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06-26-2013
Valve Spring Basics

Valve springs are among the most highly stressed components inside any high-winding racing engine. So critical are they to the success of any race engine program that many professional racers constantly their condition. Proper spring selection, installation and periodical inspection are all important, and should not be overlooked. Understanding what the valve spring is exposed to during normal engine operation is the first step in choosing the correct spring for a given application.

At the beginning of its cycle, the valve spring must compress as the valve begins to open. It must stop at maximum lift and then quickly return, allowing the valve to close. The motion must be smooth so the lifter can maintain full contact with the camshaft lobe at all times. For this to happen, the spring’s tension must be great enough to allow the lifter to follow the contour of the cam lobe, at idle and all the way through maximum RPM, for literally millions of cycles. If spring tension is too light, valve float and eventual engine damage can occur.  If the spring is too stiff, friction-related horsepower loss and accelerated valve train wear will result. According to cam experts, one of the most common causes of premature camshaft failure is the use of improper valve springs. This can include too high or too low spring pressure, or the springs can just be plain worn out.

There are a number of maladies that can befall the valvetrain if proper diligence is not applied to valve spring selection. Valve float, which can cause a sudden, dramatic loss of power, occurs when spring tension is not great enough to allow the lifter to follow the cam lobe properly. One part of the spring is trying to compress while another is trying to expand, causing the spring to overheat and resulting in permanent damage and lost tension. The spring’s erratic action causes the valve to hang open and suddenly snap closed. This can destroy valve seats, break heads off of valves, shatter retainers, bend pushrods, and cause piston-to-valve interference, resulting in bent valves and damaged pistons. Improper tension, excessive wear, heavy valvetrain components, and repeated over-revving can also contribute to valve float.

Racers who run stiff springs and repeatedly twist their engines to excessively high RPM have experienced valve spring surge, the vibration caused by the natural frequency of the spring as it is cycled. Surge can also result in valve float, and can be avoided by using an opposing spring load or damper. Opposing type inner springs are wound in the opposite direction of the outer spring and create a dampening effect. Spring dampers of flat coiled steel may also be inserted between the outer and inner springs to prevent spring surge.

Let’s assume that the proper valve spring for our application is now in hand. What else must be done to assure that the springs live for a long time and continue to perform up to their full capacities? Installing them correctly is crucial. Because of larger diameter coils, inner springs, dampers, or all three, racing springs have larger outside diameters and smaller inside diameters. For this reason, the spring seats in the heads may have to be machined to a larger size and valve guides may have to be machined as well.

Valve spring manufacturers include any pertinent information about necessary machine work in the package with the springs and most cam manufacturers offer the proper tools to get the job done right. A specification card, packaged with every camshaft or valve spring set, lists the recommended installed height, seat pressure and open pressure. Installed height is determined by how much the spring is compressed to arrive at proper seat pressure. Open pressure is the pressure exerted on the valve when it is in the open position, while seat pressure, the most critical, is the amount of pressure exerted on the valve while it is on the seat.

Now that the right springs have been installed, with the proper height and pressures, periodic inspection, including testing the springs with a seat pressure tester, is a good idea. Use a seat pressure tester that will allow the springs to be checked without removing more than the valve cover.

05-23-2013
Engine Building Tips
Engine Building
by SPEED-O-MOTIVE ©1998
There isn't a universal set of rules that govern all engine building. The following is information that has worked successfully and should be considered when building a performance engine.

A high performance race engine, by its definition, indicates that limits are going to be pushed. The limit that is of most concern, as far as pistons are concerned, is peak operating cylinder pressure. Maximizing cylinder pressure benefits horsepower and fuel economy. Considering the potential benefit, owners of non-race engines, from motorhomes to street rods, also look to increasing cylinder pressure. Increasing the compression ratio is one sure way of increasing cylinder pressure but its not the only way. Camshaft selection, carburetion, nitrous and supercharging can all alter cylinder pressures dramatically.

Excessive cylinder pressure will encourage engine destroying detonation with no piston immune to its effects. The goal of performance engine builders should be to build their products with as much detonation resistance as possible. An important first step is to set the assembled quench distance to .035". The quench distance is the compressed thickness of the head gasket plus the deck height, (the distance your piston is down in the bore). If your piston height, (not dome height), is above the block deck, subtract the overage from the gasket thickness to get a true assembled quench distance. The quench area is the flat part of the piston that would contact a similar flat area on the cylinder head if you had .000" assembled quench height. In a running engine, the .035" quench decreases to a close collision between the piston and cylinder head. The shock wave from the close collision drives air at high velocity through the combustion chamber. This movement tends to cool hot spots, average the chamber temperature, reduce detonation and increase power. Take note, on the exhaust cycle, some cooling of the piston occurs due to the closeness to the water cooled head.

If you are building an engine with steel rods, tight bearings, tight pistons, modest RPM and automatic transmission, a .035" quench is the minimum practical to run without engine damage. The closer the piston comes to the cylinder head at operating speed, the more turbulence is generated. Turbulence is the main means of reducing detonation. Unfortunately, the operating quench height varies in an engine as RPM and temperature change. If aluminum rods, loose pistons, (they rock and hit the head), and over 6000 RPM operation is anticipated, a static clearance of .055" could be required. A running quench height in excess of .060" will forfeit the benefits of the quench head design and can cause severe detonation. The suggested .035" static quench height is recommended as a good usable dimension for stock rod engines up to 6500 RPM. Above 6500 RPM rod selection becomes important. Since it is the close collision between the piston and the cylinder head that reduces the prospect of detonation, never add a shim or head gasket to lower compression on a quench head engine. If you have 10:1 with a proper quench and then add an extra .040" gasket to give 9.5:1 and .080" quench, you will create more ping at 9.5:1 than you had at 10:1. The suitable way to lower the compression is to use a dish piston. Dish (reverse combustion chamber), pistons are designed for maximum quench, (sometimes called squish), area. Having part of the combustion chamber in the piston improves the shape of the chamber and flame travel. High performance motors will see some detonation, which leads to preignition. Detonation occurs at five to ten degrees after top-dead-center. Preignition occurs before top-dead-center. Detonation damages your engine with impact loads and excessive heat. The excessive heat part of detonation is what causes preignition. Overheated combustion chamber parts start acting as glow plugs. Preignition induces extremely rapid combustion and welding temperatures melt down is only seconds away!

For a successful performance engine, use a compression ratio and cam combination to keep your cylinder pressure in line with the fuel you are going to use. Drop compression for continuous load operation, such as motorhomes and heavy trucks, to around 8.5:1. Run a cool engine with lots of radiator capacity. Consider propylene glycol coolant and low temperature thermostats. Reduce total ignition advance 2 to 4 degrees. A setting that gives a good HP reading on a 5 second Dyno run is usually too advanced for continuous load applications. Normally aspirated Drag Race engines have been built with high RPM spark retard. The retard is used to counter the effect of increased flame travel speed with increased engine heat. "Seat of the pants" spark adjustment at low RPM will almost always cause detonation in mid to high compression engines once they are rung out and start making serious horsepower. Set spark advance to make best quarter mile speed not best ET, usually 34 degrees total advanced timing.

Top Ring End Gap is often a major player when it comes to piston problems. Top ring butting under high load and heat conditions can destroy the piston top land. Most top land damage on race pistons appears to lift into the combustion chamber. The reason is that the top ring ends butt and stick tight at top-dead-center. Crank rotation pulls the piston down the cylinder while leaving at least part of the ring and top land at top-dead. Actual end gap will vary depending on the engine heat load.

Lean mixture, excessive spark advance, high compression, low capacity cooling system, detonation and high HP per cubic inch all combine to increase an engine's heat load. Most new generation pistons incorporate the top compression ring high on the piston. The high ring location cools the piston top more effectively, reduces detonation and smog, and increases horsepower. If detonation or other excess heat situations develop, a top ring end gap set to the close side will quickly butt, with piston and cylinder damage to follow immediately. High location rings require extra end gap because they stop at a higher temperature portion of the cylinder at top-dead-center and they have less shielding from the heat of combustion. At top-dead-center the ring is above the cylinder water jacket.

If a ring end gap is measured on the high side, you improve detonation tolerance in two ways. One, the engine will run longer under detonation before rings butt. Two, some leak down appears to benefit oil control by clearing the oil rings of oil build up. Clean, open oil rings are necessary to prevent from reaching the combustion chamber, which is also why we do not like gapless rings. A very small amount of chamber oil will cause detonation and produce significant horsepower loss. Top ring gaps can be increased 50% with hypereutectic pistons.

Ring Options of 1/16" or stock 5/64" are offered on most performance pistons. The 1/16" option reduces friction slightly and seals better above 6,500 RPM, while being considerably more expensive. Stock, (usually 5/64" compression rings), work well and help with the budget.

Piston to Bore Clearance for hypereutectic pistons were Dyno tested at wide open throttle with .0015", .0020", .0035" and .0045" piston to bore clearance. After 7-1/2 hours the pistons were examined and they all looked as new, except the tops had normal deposit color. Even with 320 degrees Fahrenheit oil temperature, the inside of the piston remained shiny silver and completely clean. Excessive clearance has been shown to be safe with hypereutectic pistons. Loose Hypereutectic pistons over .0020" do make noise. As they get up to temperature they still make noise because they have very restricted expansion rate and do not swell up in the bore. The Hypereutectic alloy not only expands 15% less, it insulates the skirts from combustion chamber heat. If the skirt stays cool piston expansion is drastically reduced. Running close clearances is beneficial to piston ring seal and ring life. A small short term HP improvement can be had by running additional piston clearance because friction is reduced. To obtain actual piston diameter, measure the piston from skirt to skirt level with the balance pad.

Pin Oiling should be done at pin installation, whether it is pressed or full floating, prelube the piston pin hole with oil or liquid prelube, never use a grease. If you are using a pressed pin rod be sure to discard spiral pin retainers. A smooth honed pin bored surface with a reliable oil supply is necessary to control piston expansion. A dry pin bore will add heat to the piston rather than remove heat. Pistons are designed to run with a hot top surface, and cool skirts and pin bores. High temperature at the pin bore will quickly cause a piston to grow to the point of seizure in the cylinder

Marine Applications require an extra .001"-.003" clearance because of the possible combination of high load operation and cold water to the block. A cold block with hot pistons is what dictates the need for extra marine clearance.

"Compression Ratio" as a term sounds very descriptive. However, compression ratio by itself is like torque without RPM or tire diameter without a tread with. Compression ratio is only useful when other factors accompany it. Compression pressure is what the engine actually sees. High compression pressure increases the tendency toward detonation, while low compression pressure reduces performance and economy. Compression pressure varies in an engine every time the throttle is moved. Valve size, engine RPM, cylinder head, manifold and cam design, carburetor size, altitude, fuel, engine and air temperature and compression ratio all combine to determine compression pressure. Supercharging and turbo-charging can drastically alter compression pressures.

The goal of most performance engine designs is to utilize the highest possible compression pressure without causing detonation or a detonation related failure. A full understanding of the interrelationship between compression ratio, compression pressure, and detonation is essential if engine performance is to be optimized. Understanding compression pressure is especially important to the engine builder that builds to a rule book that specifies a fixed compression ratio. The rule book engine may be restricted to a 9:1 ratio but is usually not restricted to a specific compression pressure. Optimized air flow and cam timing can make a 9:1 ratio but is usually not restricted to a specific compression pressure. Optimized air flow and cam timing can make a 9:1 engine act like a 10:1 engine. Restrictor plate or limited size carburetor engines can often run compression ratios impractical for unlimited engines. A 15:1 engine breathing through a restrictor plate may see less compression pressure than an 11:1 unrestricted engine. The restrictor plate reduces the air to the cylinder and limits the compression pressure and lowers the octane requirements of the engine significantly.

At one time compression pressure above a true 8:1 was considered impractical. The heat of compression, plus residual cylinder head and piston heat, initiated detonation when 8:1 was exceeded. Some of the 60's 11:1 factory compression ratio engines were 11:1 in ratio but only 8:1 in compression pressure. The pressure was reduced by closing the intake valve late. The late closing, long duration intake caused the engine to back pump the air/fuel mix into the intake manifold at speeds below 4500 RPM. The long intake duration prevented excess compression up to 4500 RPM and improved high RPM operation. Above 4500 RPM detonation was not a serious problem because the air/fuel mix entering the cylinder was in a high state of activity and the high RPM limited cylinder pressure due to the short time available for cylinder filling.

Before continuing with theory, a little practical compression information is in order. If you have a 10:1 engine with a proper .040" assembled quench and then add an extra .040" gasket to give 9.5:1 and .080" quench you will usually experience more ping at the new 9.5:1 ratio than you had at 10:1. Non quench engines are the exception to this rule. Some racers make the effort to convert non-quench engines to quench type engines, as with our Mopar Squish Deck Heads. Compression ratios that work are as follows:

PUMP FUEL

8.5:1- Non-quench head road use standard sedan, without knock sensor.

8.5:1- Quench head engine for tow service, motorhome and truck.

9.0:1- Street engine with proper .040" quench, 200° @ .050" lift cam, iron head, sea level operation.

9.5:1- Same as 9:1 except aluminum head used.

Light vehicle and no towing.

10:1- Used and built as the 9.5:1 engine with more than 220° @ .050" lift cam. A knock sensor retard is recommended with 10:1engines.

RACE GAS

12.5:1- Is the highest compression ratio suggested with unrestricted race gas engines.

ALCOHOL

15.5:1- Is the highest compression ratio suggested for unrestricted alcohol fuel engines.

Satisfactory use of 14:1 - 17:1 compression engines can be made when restrictor plate or small carburetor use is mandated by the race sanctioning. High altitude reduces cylinder pressure so if you only drive at high (above 4500 feet altitude) a 10:1 engine can be substituted for a 9:1 compression engine. General compression rules can be violated but is usually a very special case such as a 600 HP normally aspirated engine in a 1500 lb. street car with a 12:1 compression ratio. The radical cam timing necessary for this level of performance keeps low and medium RPM cylinder pressure fairly low. At high RPM detonation is less of a problem due to chamber turbulence, reduced cylinder fill time, and the fact that you just can't leave the above combination turned on very long without serious non-engine related consequences.

Piston temperature and horsepower are interrelated. High horsepower per cubic inch engines not only make more horsepower but they make more heat. How the excess heat is handled has a significant effect on total engine power and longevity.

Various piston, cam, valve, chamber and port configurations have been and are currently being tested to optimize engine internal temperatures. Some engines have ceramic exhaust port insulation coatings that allow cooler cylinder head operation while keeping exhaust temperatures elevated for efficient catalytic converter operation. The same ceramic type insulation on a piston top has been quite successful. Ideal piston temperatures in an operating engine would suggest refrigeration during the intake and compression stroke, and incandescence during the combustion and exhaust stroke. The advantage of a hot piston on the power stroke is that less combustion energy is going to be absorbed by the piston. So far, it is not practical to heat and refrigerate a piston 6000 times a minute. However, if the incoming air is not heated by the piston and the piston reflects the heat of combustion, you start to approach ideal conditions. A polished hypereutectic piston will reflect combustion heat back into the combustion process. This reflection, combined with the insulating qualities of the hypereutectic alloy, keeps the heat in the cylinder during the power stroke. A smooth polished piston runs cooler than a non-polished piston, even after combustion deposits have turned both pistons black. A cool, smooth piston will transmit a minimum of heat to the incoming fuel air mix.

The Hypereutectic piston gives the racer a real out of the box advantage with smooth diamond turned piston heads. A polish is relatively easy to achieve and does improve the already excellent reflectivity of the hypereutectic piston. If a buffing wheel is used, you will note a gray cast to the finished piston. The gray results from the exposure of the Silicon particles that are dispersed through the piston.

Experimental work to reduce piston heating of the incoming fuel mix has been very limited but, in theory, a thin ceramic coating may prove to be beneficial. A thin, smooth coating over a polished piston should still reflect combustion heat while reducing carbon buildup and protecting the piston polish. It is easier for a thin film to change temperature with each engine cycle than it is for the whole piston to do the same. A thin film can be cooled by the first small percentage of inlet fuel mix, allowing the main quantity of fuel mix to remain relatively cool. Tests have shown that polishing the combustion chamber, valves and piston top can increase horsepower and fuel economy by 6%.

All this polishing probably sounds counter to the practice of cimpling the combustion chamber. Dimpling has been show to put wet flow back into the air flow and improve combustion. We do not recommend dimpling, but do suggest cutting a small discontinuity close to the valve seat to turbulate wet flow. Some bench flowed cylinder heads encourage fuel separation at the inlet pot. If a small step is added at the valve seat to force the wet flow over the resulting sharp edge, fuel will reenter the air stream and give you the same affect as dimpling only without losing the benefit of a completely polished chamber. As you reduce wet flow you will improve combustion and most likely need to install leaner carburetor jets. Leaner jets compensate for the excess fuel that is available when wet flow is put back into the air/fuel mix. Significant additional horsepower gains can be had with careful attention to cylinder-to-cylinder fuel distribution by allowing all cylinders to be set "just right".

Combustion chamber design work has increased steadily the last ten years. Some of the work is mandated by the EPA and some is the result of race engine development. Some of the smog work has actually enhanced race engine development. Combustion chamber science is now more concerned with the effects of swirl, tumbling, shrouding of the valve, quench, flame travel, wet flow and spark location. A combustion chamber shaped dished piston can improve the flame travel in the combustion chamber. A dish allows the flame to travel further and expand more before it is stopped by a metal surface. This rapid flame travel makes it unnecessary to run big spark advance numbers. Ideally, we would like to be able to initiate ignition at top dead center since this would reduce negative torque in the engine that is now cause by spark advance. We are some time away from a practical spark ignition system that will make optimum power with a TDS setting. Some day it will happen. Don't go out and buy dished pistons for your open chamber 454. The advantage in flame travel is more than offset by the low compression ratio this combination yields. Small combustion chambers respond well to dished pistons, especially reversed dome or "D" cups. A 400 small block Chevy can use a 22CC D Cup piston and still have 10.4:1 compression. The trend in modern engine design seems to be smaller combustion chambers with recessed piston tops for more HP per cubic inch.

Ignition timing on most installations should be 34 degrees total with full mechanical advance dialed in. More advance may feel better off the line but the engine lays down as the combustion chamber components come up to temperature. At the drag strip set timing for maximum MPH not best ET. Too much spark advance will shorten the life of any performance engine, sometimes drastically.

Nitrous oxide can double the horsepower of most engines with less effort and money being spent than any other modification. Even the "smog people" are usually happy, as the nitrous is activated only during full throttle "open loop".

A nitrous engine can be built as a stock rebuild or it can be a dedicated effort to maximize the total performance package. As more power is generated, more waste heat, exhaust air flow and combustion pressures push the limits of engine strength. Often more beef is needed in the drive train and tires.

All stock factory engines are built with a safety factor when it comes to RPM, HP produced, cylinder pressure, engine cooling, etc. If you are only going to use a 100 HP nitrous setup on a 300 cubic inch or larger engine, built in factory safety factors are probably sufficient. As power output levels are raised engine modifications are usually prudent.

The most common mistake made when using nitrous oxide injection concerns ignition timing. A normally aspirated engine makes its best power when peak cylinder pressures occur between 14 and 18 degrees after TDC. Pistons usually require 34 degrees BTDC ignition timing at full mechanical advance to achieve proper ATDC peak cylinder pressure. The total time from spark flash to the point of peak pressure is typically 48 to 52 degrees. If an engine is producing 30% of its power from nitrous, the maximum cylinder pressure will occur too close to TDC to avoid run away to detonation. If ignition does not get retarded, good-bye horsepower and head gaskets. The key to getting max HP from a max nitrous engine is to shift the maximum cylinder pressure event progressively further after TDC.

Cylinder pressure of 1000 PSI at TDC, (FIG. 1), can drop to 500 PSI with less than 3/8" of piston travel, (FIG. 2). If you can manage to get 1000 PSI in the same engine after the 3/8" travel, (FIG. 3), the pistons will have to travel an additional 3/4" to lower the cylinder pressure to 500 PSI, (FIG. 4). Work is defined as a force times distance. An average pressure, (750 PSI X 12-1/2 sq. in.), times distance in feet, (3/8" divided by 12), equals 293 foot pounds of work. Our second example, because it has twice the chamber volume above the piston location, must move twice as far to lower the cylinder pressure by 1/2. Since all the other numbers, by our own definition are the same, the force multiplied by a distance twice that of the first example will equal twice the work done, 586 foot pounds of work. There is no free lunch in horsepower equations because to get 1000 PSI above the piston in the second example takes twice as much fuel and energy as the 1000 PSI in the first example. What this offsetting of the peak pressure does is allow us to use the extra fuel mix available to a nitrous engine without breaking and melting things. The system that allows us to postpone maximum cylinder pressure is ignition timing retard. To a lessor extent short rod ratios, lower compression ratios, high RPM, aluminum heads, a tight quench, a rich fuel mixture, a small carburetor and hotter cams tend to delay maximum cylinder pressure.

Understand that, in our quest to delay cylinder pressure's peak time, more is not necessarily better. Instead, consider that the ideal cylinder pressure would be just short of detonation pressure and this pressure would be maintained from top dead center, and as long as possible after TDC. If timing is really late, you won't build enough cylinder pressure to start the car, let alone drive it. The 1000 PSI pressure in the example is not the maximum allowable combustion pressure but, rather, a comfortable pressure for illustration of the work principle.

Some nitrous manufacturers recommend, "retard the timing two degrees for each fifty horse power of nitrous". Other nitrous kits have the flame speed artificially slowed by the intentional use of a rich fuel to nitrous ratio. The maximum performance engine with a heavy nitrous load must achieve peak cylinder pressures, with the combustion chamber size being drastically increased due to the piston being on its way toward bottom dead center. The strongest engines have less compression ratio, less spark advance, and more nitrous.

Many people just don't like the idea of any retard. They say, "retard timing and exhaust heat goes up". It usually does in a stock non-nitrous engine because lower peak cylinder pressure slows the burning. If the timing is retarded in a non-nitrous engine, the exhaust opens before the fuel mix is finished burning and exhaust temperatures go up. Piston temperatures usually go down and exhaust valve temperature goes up. In the nitrous engine, exhaust temperature goes up for several reasons. The first is that the power output has gone up considerably. More power usually produces more waste heat. Second, the need to keep maximum cylinder pressures within reason has dictated that the biggest part of the fire happens closer to the exhaust valve opening time. There just isn't enough piston travel to extract all the energy out of the charge before the exhaust valve opens. Now, we could and sometimes do, open the exhaust valve later so more combustion pressure energy can be used to turn the crank. The trade off is negative torque on the exhaust stroke. If we still have significant cylinder pressure in the cylinder as the piston moves from BDC to TDC on the exhaust stroke, your net HP falls drastically. A real problem at higher RPM.

You can improve maximum power stroke efficiency and minimize exhaust pumping losses by running the engine at lower RPM and/or improving the exhaust valve size, lift and port design. A big nitrous engine likes everything about the exhaust to be big. If it flows good enough the cylinder will blow down by bottom dead center, even at high RPM with relatively mild exhaust valve timing. There are many variables in the design and development of an all out nitrous engine. A mistake will cause the melt down of any piston. The high strength of the hypereutectic piston will withstand detonation and severe abuse. Unfortunately, all pistons, even forged will melt and when cylinder pressure limits are exceeded, run away detonation can occur. The excess detonation heat makes the plugs, valves and pistons so hot the ignition system alone cannot be used to shut the engine down. Continued operation worsens the situation to the point of a total melt down. Designing a maximum performance nitrous engine is more of an exercise in heat management than it is in engine building. Serious nitrous users should review our list of ceramic coatings.

A lack of a sufficient fuel supply is probably the most common killer of the nitrous engine. If you add a 300 HP kit to your present 300 HP engine, your fuel requirements roughly double and a shortage doesn't just slow you down, it melts things. An electric fuel pump and fuel line devoted entirely to the nitrous equipment is recommended. If you are using a diaphragm mechanical pump to supply fuel to the carburetor, it is worth while to increase the fuel line I.D. If the carburetor goes lean while the nitrous is on, the pistons can melt even with a rich fuel line trick (1/2" dia.) only makes a major improvement in the operation of diaphragm mechanical pump is not recommended and does not do well at high engine RPM. A large size line is effective with a mechanical pump, even if you use smaller fittings at the tank, fuel pump and carburetor. The advantage of the 1/2" large line is not related to the steady state flow rate of the line.

The advantage relates to the acceleration time and displacement of the pulsating flow common to the mechanical pump.

High compression ratios can be used with nitrous but shifting the maximum pressure after top dead center becomes more and more difficult. I prefer to use street compression ratios and then just work with adding more nitrous to get desired horsepower levels.

We are currently testing some pistons specifically designed for Nitrous use. Current "off the shelf" pistons have been successfully run with a 500 HP nitrous kit combined with a nitrous control system. Most of our effort has been to develop new ideas that will push the limit of nitrous technology. More testing is planned with a piston especially coated to reduce detonation.

When choosing piston rings for an engine the most important factor is the intended use of the vehicle. A piston ring set that delivers excellent street performance may not be correct for an engine that will see competitive action, or for one that will be used with nitrous oxide.

Piston rings serve two purposes - to contain the cylinder pressure, and to prevent oil from getting into the combustion chamber. Sealing against pressure leakage, or "blow by", is the responsibility of the top ring. The keys to good ring sealing are cylinder wall finish and piston ring groove condition. If pressure gets past the top ring it is already "lost". Any such leakage will not be ignited by the spark plug, and is unlikely to produce any significant power, even if captured between the first and second ring. The second ring is primarily an oil control device. If the top ring is doing the job, the second ring will see fairly limited combustion pressure. Some companies sell second rings that use complex or fragile designs for sealing. These are prone to premature wear and have unpredictable behavior at high RPM levels. Cylinder leakage test percentages are only useful for comparison to data generated when an engine was fresh. Unfortunately this kind of information can be misrepresented to show very low leakage numbers by folks trying to sell "trick" parts. Leakage tests are steady state - they do not account for time, piston movement, or true operating pressures. "Blow-by" measurement will give a better picture of ring condition, but on track performance is the only real measurement of success. Our moly rings are intended for applications where cost is of prime importance.

Engines being built for serious competition will be far better off using Plasma Moly ring sets. These feature an extremely durable ductile iron top ring with Plasma Moly facing. This design allows the ring to seat quickly and to maintain its sealing integrity under the severe stress of racing. The second ring is a special low tension plain iron design. These taper faced rings are specifically designed to break in quickly and to keep oil from migrating into the combustion chamber. The SS50U stainless steel oil control rings are the absolute best in the high performance industry. This ring combustion gives dependable sealing and allows maximum power production.

RING TENSION

Piston ring sets are available with either standard or low tension oil rings. The standard tension rings are recommended for street driven applications, and for race vehicles which may see frequent open to closed throttle transitions in use - such as road racing. They are also useful in engines that may experience cylinder bore distortion during operation.

Low tension oil rings deliver increased performance due to their reduction in cylinder wall drag. These are highly recommended for many racing applications. Engines using low tension rings should be built with particular attention to cylinder concentricity, and often benefit from the use of a crankcase vacuum system.

RING END GAP CLEARANCE

The piston ring's end gap can have a significant effect on an engine's horsepower output. Rings are available both in standard gap sets, and in special "file fit" sets. The file fit sets allows the engine builder to tailor the ring end gaps to each individual cylinder. Ring gaps should be set differently dependent upon the vehicles use, within the range of .003" (for the 2nd. ring) to .004" (for the top ring) per inch of cylinder diameter. The more severe the use, the greater the required end gap (assuming the use of similar fuels and induction systems). Engines having low operating temperatures, such as those in marine applications is too small. The chart below is a general guideline for cylinders with a 4.00" bore, adjust the figures to match your engine's cylinder diameter:

Top Rings (ductile iron, 4" bore)

Supercharged

Nitromethane .022 - .024"

Alcohol .018 - .020"

Gasoline .022 - .024"

Normally Aspirated - Gasoline

Street, Moderate Performance .016 - .018"

Drag Racing, Oval Track .018 - .020"

Nitrous Oxide - Street .024 - .026"

Nitrous Oxide - Drag .032 - .034"

2nd Rings (plain iron, 4" bore)

Supercharged

Nitromethane .014 - .016"

Alcohol .012 - .014"

Gasoline .012 - .014"

Normally Aspirated - Gasoline

Street, Moderate Performance .010 - .012"

Oval Track .012 - .014"

Pro Stock, Comp. .012 - .014"

Nitrous Oxide - Street .018 - .020"

Nitrous Oxide - Drag .024 - .026"

INSTALLATION NOTES -

CYLINDER WALL FINISH

When installing new rings, the single greatest concern is the cylinder wall condition and finish. If the cylinders are not properly prepared, the rings will not be able to perform as designed. The use of a torque plate, head gasket, and corresponding bolts are necessary to simulate the stress that the cylinder head will put on the block. Main bearing caps should also be torqued in place. The correct procedure has three steps. First the cylinder is bored to approximately .003" less than the desired final size. Next it is rough honed within .0005" of the final diameter. Then a finer finish hone is used to produced the desired "plateau" wall texture. Use a 280 - 400 grit stone to finish cylinder walls for Plasma Moly rings.

Note - the "grit" number we are referring to is a measurement of roughness, it is not the manufacturers stone part number (a Sunnen CK-10 automatic hone stone set #JHU-820 is 400 grit). The cylinder bores should be thoroughly scrubbed with soap and hot water and then oiled before piston and ring installation.

Piston ring grooves are also sealing surfaces, and must be clean, smooth and free of defects. Ring side clearance, measured between the ring and the top of the groove, should be between, .001" and .004".

by SPEED-O-MOTIVE ©1998
http://www.speedomotive.com
04-26-2013
Engine RPM and Valvetrain

It’s all about rpm, baby. In just about every racing class in existence that limits maximum displacement, the quest to turn more rpm than the next guy rules the day. In classes where power adders are prohibited, it’s quite easy to understand why this is the case. Once an engine builder has squeezed every last cfm out of a cylinder head, and torque output plateaus, the only way to increase horsepower is to turn more rpm. For proof, you needn’t look farther than an 11,000-rpm NHRA Pro Stock motor, or the 9,500-rpm mills in NASCAR Sprint Cup. The most extreme example of the importance of rpm is in Formula 1. Not long after the sanctioning body cut down max displacement to 2.4 liters in 2006, engines started spinning up to 20,000 rpm. Consequently, now in F1 there’s a cap on both displacement and maximum rpm. As impressive as those lofty revs may be, the use of pneumatic valvesprings in F1 motors makes them difficult to relate to for 99.9 percent of hot rodders. In some respects, it’s much more difficult to turn half as many rpm with mechanical springs. To learn the intricacies of building an ultrahigh-rpm valvetrain, we contacted some of the best in the business. Our panel of experts includes Judson Massingill of the School of Automotive Machinists, Darin Morgan of Reher-Morrison, Phil Elliot of T&D Machine, and COMP Cams. Follow along as we show you how to give your tach a beat-down.

 

 

Valvetrain Advances

 

Judson Massingill: Valvetrain technology has gradually progressed over the years, addressing one weak link after the next. In the late ’80s, we had the ramp technology built into the cam lobes that would have enabled the level of rpm engines are turning today, but we didn’t have the valvesprings to control them. Then by the early ’90s, the valvesprings were much improved, but the lifters started breaking due to all the additional spring pressure. Typically, the axles for the roller wheels or the axle supports were the first area to fail. To address this issue, the aftermarket came out with true race lifters that moved the limit of rpm back to the springs. At this time, the valvespring and lifter technology were adequate for the rpm motors were turning, but racers being racers, they always tried to wring a couple of hundred extra rpm out of their motor. If a company like COMP Cams tested a valvetrain to 9,000 rpm on a Spintron, sure enough, racers would spin their motors to 9,200 rpm. At this point, the weak link became the rocker arms. The stud-mounted rockers of the day just weren’t able to handle the spring loads and rpm that race motors demanded. Once again, the aftermarket responded by developing shaft-mounted rocker arms. Shaft-mount rockers were around long before this time, but they weren’t really necessary because we didn’t have the spring and lifter technology to take advantage of them. With the rocker issue solved, that put the rpm limitation back on the valvesprings. As you can see, it’s not a single component that’s responsible for what has enabled modern race engines to turn more rpm than anyone could have imagined just 5 to 10 years ago. It’s a tapestry of elements that had to come together to make it happen.

Darin Morgan: Valvetrain technology has come a long way in the last 10 years, but like anything else in the development process, you can’t put your finger on one single thing that’s responsible for the forward progress. It’s been a combination of many small advances and failures that got us to the point where we are now. Back 20-25 years ago, we were running stock diameter cams that had lots of resonance. Even if we had the best springs in world, we couldn’t turn more than 9,500 rpm. As soon as engine builders stepped up to 55mm cores, the valvespring technology wasn’t there. Between 1999 and 2003 is when big changes started to happen. By then, we had even larger 60mm cam cores along with the valvespring and cam lobe ramp technology to turn lots of rpm. Before, we used to brutalize the valvetrain, which is the wrong way to do it. Now we finesse the valvetrain to loft it over the nose of the cam. It’s hard to predict where things will go in the future, but the current trend is stepping up to larger core cams and using lifters with bigger wheels to improve valvetrain control at higher rpm. At the Pro Stock level, we start losing control at 10,800 rpm. For engines in the 350 to 380ci range, the ceiling is 11,000 rpm. At Reher-Morrison, we just built a 363ci small-block that makes 1,040 hp at 10,100 rpm naturally aspirated. Numbers like that would have been unheard of just five years ago. The important thing to remember is that every engine is its own animal. You can’t take the valvetrain from one engine and put it in another one and expect it to work perfectly.

 

Shaft Rockers

 

 

 
How To Increase Engine Rpm Rockers
 
Judson Massingill: As rpm and valvespring pressure increases, the studs on a pedestal-mount rocker arm’s setup will flex and eventually break. Mounting the rocker arms on a shaft instead of a stud increases rigidity tremendously, and therefore shaft-mount rockers are a must in high-rpm race motors. That said, rigidity is just part of the equation. Shaft-mount rockers also make it much easier to achieve proper valvetrain geometry. With a stud-mounted rocker system, the only way you can adjust the geometry is with different length pushrods. On the other hand, with shaft-mounted rockers the centerline of the pivot point of the rockers can be positioned perfectly in relation to the tip of the valve, since the rockers are mounted on a stand. All you have to do then is measure for the correct length pushrods afterward. It is this combination of improved geometry and rigidity with shaft-mount rockers that enable turning more rpm.

 

Phil Elliot: Valvetrain stability is what everyone is after, and shaft-mount rockers are a great way to accomplish this. Years ago, people put plexiglass on valve covers, and recorded the valvetrain movement with a high-speed camera. They were scared by how much things moved around even with stud girdles. This reinforced what racers had known all along, which is that stud-mounted rockers didn’t provide enough stability in race motors. The notion that you need to step up to shaft-mount rockers at a certain rpm is a bit misleading. The stress imparted on a rocker arm is a product of both spring pressure and rpm. Spring pressure is actually what tries to rip the stud out of head. Fortunately, race engine builders don’t have to deal with all the design parameters that the OEMs have to. In racing we don’t need to worry about whether or not the valve covers will fit under an A/C compressor. We just build a new valve cover that will fit around the cylinder head and rocker arms.

 

Lofting

 

Darin Morgan: At the Pro Stock and Comp Eliminator level, the increases in horsepower we’re seeing today are directly related to the loft curve built into the cam. Do it right, and it’s like having a variable-duration camshaft. At 8,000 rpm is where the loft curve comes into play. Generally, a smooth loft curve will give an additional 0.008 inch of lobe lift by 8,000 rpm. That figure increases with rpm, so by 10,000 rpm you end up with an extra 10-15 degrees of duration. However, accomplishing this is much easier said than done. You want as much valve speed as you can get, but you have to balance it with the proper rate of valve acceleration to maintain valvetrain control. The rate of the springs, and the weight of the coils, retainers, and locks must all be optimized. With larger base circle cams we can now get up to 0.600-inch lobe lift. This allows us to use lower ratio rockers so the initial valve acceleration isn’t as quick, which helps stabilize the valvetrain.

 

Valvesprings

 

 

 
How To Increase Engine Rpm Springs
 
Judson Massingill: Getting the valvesprings to live isn’t difficult if you have a limited amount of valve lift. However, cylinder head technology has improved dramatically in the last 10-15 years, so now we’re picking up the valves much more than ever before. That puts much more stress on the valvesprings. For a while, the focus was on the metallurgy, wire thickness, and alloy of the springs, but several years ago manufacturers realized that impurities in the spring wire were causing them to break. As a result, using clean wire in the springs is a top priority these days. Furthermore, what we’ve learned in the last four to five years is that you don’t need enormous spring diameters anymore. Not too long ago, we used to have double- and triple-duty springs with 1.600-inch diameters. What happened was that the springs were getting so big and heavy that you needed higher spring rates just to control the weight of the spring. With the better, cleaner metal we have these days, engine builders are using smaller-diameter springs. Smaller springs also let you use smaller retainers, which further reduces valvetrain mass. A great example of this is a beehive valvespring. By reducing the diameter of the top of the spring, it cuts down on mass as well. Our ’99 Camaro drag car has an LS motor that turns 9,600 rpm. The exhaust valvesprings are just 1.550 inches, but they have 1,000 pounds of open pressure.

 

COMP Cams: In recent years, a lot of progress has been made with regard to valvesprings. One of the newer trends is that we are now designing springs for specific applications. In the past, we would try to find a spring that we thought would suit a specific engine combo. In a lot of cases now, we will create a clean-sheet design to get the spring ideally matched to the rest of the system. The biggest advantage to the newer springs is the reduction of mass. I’ll also say we have only started to scratch the surface with regard to spring design and materials. The metallurgy, spring design, and overall size of the spring all contribute to the performance of a spring.

 

Fighting Flex

 

 

 
How To Increase Engine Rpm Valves
 
Judson Massingill: You can spend all kinds of time and money designing the best cam in the world, but unless you can get the valve to properly follow the lobe profile, all that R&D work is worthless. Any flex in the valvetrain means that the valves are not doing what the cam wants them to do. The goal is to have extremely stiff parts, and this is particularly true with the pushrods. Up until the early ’90s, engine builders thought that as long as the pushrod didn’t bend, everything was OK. Now we’ve learned that even if a pushrod doesn’t bend, it can still flex tremendously. To combat this, the trend these days is to use giant diameter pushrods. In racing classes that allow it, using a shorter deck height block is also common. This allows using shorter pushrods, which reduces both pushrod flex and mass. In fact, GM Performance Parts sells low deck height small-block Chevy blocks that have an 8.325-inch-tall deck opposed to a standard 9.025-inch tall deck.

 

 

Spintron Testing

 

Darin Morgan: The Spintron is a great tool that helps simulate valvetrain dynamics, but it by no means has the final answer for everything. Interestingly, a loft curve that looks great on the Spintron does not necessarily correlate to good numbers on the dyno and at the track numbers. That’s because a Spintron can’t simulate the crankshaft pulsations that are transmitted into the cam belt and valvetrain. It’s just another example of why there is no substitute for real-world testing. Only after dyno testing can you begin fine-tuning the loft curve.

 

Big Journal Cams

 

Judson Massingill: Camshafts with larger journal diameters definitely decrease how much the cam flexes, but one of the biggest advantages of larger journals is much simpler to understand. When you’re sliding a cam into a block, the amount of lift you can pack into the lobes is limited by the size of the cam bores. If you make the lobes too big, the cam won’t physically fit inside the block. That’s where big journal cams come into play. Many aftermarket blocks are available with larger diameter cam bores. This allows installing a cam with larger, more aggressive lobes. To achieve any given amount of valve lift, you generally want the most lobe lift as possible with the lowest rocker arm ratio possible to help stabilize the valvetrain. The reason why NASCAR Sprint Cup teams use 2.4:1 rockers is because they have to run flat-tappet cams that can’t accelerate the lifters as fast as a roller lifter motor. Since they can’t run as much lobe lift as they’d like to, they have to make up for it with higher-ratio rockers. If you’re racing in a class that allows it, using a larger journal cam with bigger lobes and a lower rocker ratio is a better way of achieving high valve lifts. With a 50mm cam, about .440-inch lobe lift is the limit and with a 60mm cam you can get about 0.590-inch lobe lift.

COMP Cams: The barrel diameter of a camshaft plays a big role in the overall stiffness of the valvetrain. In high-rpm applications, it’s best to opt for the largest journal diameter you can get for a specific engine. The base circle of a cam lobe is determined by journal diameter and lobe lift. When starting from a standard journal, whether small- or big-block, going to a larger journal will increase your barrel diameter and base circle size. There are blocks available now that feature raised cam locations. Furthermore, I would advise anyone not to let the stroke or rods dictate your base circle size. When designing the 400 small-block, there is a reason why Chevrolet made changes to the connecting rod in order to clear the cam instead of using a smaller base circle cam. Doing so would have been cheaper than designing a new connecting rod, but bigger is always better with regard to the size of the base circle.

 

Resonance

 

 

 
How To Increase Engine Rpm Valvesprings
 
Darin Morgan: Every component in the valvetrain has a natural resonant frequency, so you have to design a motor to avoid those points. Sometimes, the only way to do that is through trial and error. One example that comes to mind is a particular valvespring we used in one of our crate motors that worked great in drag cars. When those same motors were used in boats, however, the springs started breaking. What we discovered was that the springs had a natural resonance at 7,400 rpm, and if held there long enough, they would get excited and eventually break. That wasn’t an issue in a drag application, but became a problem in boat motors that ran at sustained engine speeds. The adverse effects of resonance are also why it’s so important to use the stiffest pushrods possible. When a pushrod flexes, it stores energy and then releases it later in the lift curve, causing resonance. Reducing weight isn’t as important on the pushrod side of a rocker as on the valve side, so we now use large 9/16- and 3/4-inch diameter pushrods on high-rpm race motors.

 

 

Where to Cut Weight

 

COMP Cams: Reducing mass, or weight, is more critical on the valve side of the rocker arm than on the pushrod side. From the rocker arm to the lifter, increasing stiffness will be more advantageous than reducing mass every time. The goal here isn’t to go after the lightest weight parts when considering a lifter or pushrod. The top priority is increasing stiffness and reducing flex. With regards to pushrods, I would recommend going with the largest diameter, thickest-wall pushrods you can fit in an engine. On the valve side of the rocker arm, weight is much more important. Here, it’s critical to get the locks, retainers, and springs as light as possible to reduce inertia.

 

Reducing Mass

 

Judson Massingill: After a valve is accelerated to maximum lift, it comes to a stop and then completely reverses direction as it closes. This makes it difficult to stabilize the valvetrain and keep it out of float since it is constantly fighting this inertia. That’s why reducing valvetrain mass is so important. Titanium engine parts have been around since the ’80s, but now they’re more readily available. To shave every last gram possible, modern race engines have titanium valves, retainers, and locks. Engineers are literally looking everywhere to reduce mass. It wasn’t enough to just make a valve out of titanium. Valve manufacturers started reducing the diameter of the stem, down the 7mm in some cases, and now they’re hollowing out the stems as well. That might seem extreme, but a motor doesn’t know what cam it has in it. All it knows is valve movement, and reducing mass and inertia is critical to achieving valvetrain stability. To put things into perspective, there’s a story of a motor Richard Childress Racing built for its NASCAR Sprint Cup cars several years ago. It had a cam that was worth 8-10 hp more than the grinds they were using before, but the motor would only last 300 miles before the valvetrain broke. By simply removing three grams off the valve side of the rockers, the motors lasted the full 500-mile race distance.

Phil Elliot: Every time a rocker arm moves, it has to start, stop, and then change directions. Naturally, at T&D we’re always trying to reduce mass as much as possible to cut down on inertia. When you remove mass, it’s easier to keep the valvetrain in control. In addition to working closely with race teams, we perform extensive stress tests to see how much we can get away with. We put our rockers through fracture tests that bend the rockers until they break. Likewise, we put our parts in Sprintrons and really try to wreck them. An analogy we like to use is that if a 2x6 is too big, then we use a 2x4 instead. Even so, you can’t take things too far and compromise durability. Lighter is better to point, but parts can’t get too light.

 

Little Tricks

 

Judson Massingill: Oftentimes it’s a combination of lots of little tricks that help extend the rpm potential of an engine. For example, longer valves enable using taller valvesprings. Likewise, these days it’s common to run cupped pushrods in race motors. Instead of having a cupped section in the rocker arms, with cupped pushrods the ball portion is on the rocker arm and the end of the pushrod is cupped. This allows running much higher rocker arm ratios and spring pressures before everything binds up. Circle track racers were the first to experiment with cupped pushrods, and now they’re trickling over to drag motors as well. Interestingly, some factory FE Ford and Chrysler motors used cupped pushrods. Another trick we’ve learned from the NASCAR guys is building aluminum tubes with oiling jets into the valve covers that direct oil directly onto the valvesprings. This helps keep them cool and extends durability. Another benefit of this arrangement is that it allows running less oil to the top end of the motor. While we’re on the topic of springs, it’s worth mentioning that we’re no longer setting them up like we used to. In the past, we used to think that running them close to coil bind was a bad thing. Now we’ve learned that in motors that turn 9,300 rpm or more, regardless of what the spring pressure is, we set them up 0.060 inch from coil bind. This helps kill harmful valvetrain harmonics. CHP



Read more: http://www.chevyhiperformance.com/tech/engines_drivetrain/cams_heads_valvetrain/1111chp_how_to_increase_engine_rpm/viewall.html#ixzz2Ra1QO5IJ

03-28-2013
How Valve Springs Work

Although the basic purpose of a valvespring is to close the valve while also ensuring that the valvetrain stays in contact with the cam lobe, it must perform this feat under grueling conditions that vary tremendously several times every minute. The expected rpm range, camshaft profile, and cylinder-head design just begin the list of criteria for choosing the right valvespring. Yes, like almost everything in the automotive arena, parts need to be matched to the performance level of the engine to perform their best. Use old valvesprings, ones with the wrong pressure, or install them improperly, and you'll wonder why your engine doesn't perform as well as your buddy's. For this month's "How It Works" segment, we're going to look into the world of valvesprings as they pertain to a conventional Chevrolet engine. As we often mention, volumes could be written on this ever-evolving topic (and have been), but in these next few pages we'll cover the overall qualities of valvesprings and some important things to consider when purchasing or installing your next set.

It's a Spring Thing
In general, a valvespring produces a load based on how much it is squeezed. The valvespring's rate is dependent on the number of coils, wire diameter, shape (not all valvesprings are uniform), and outer diameter (OD), and its pressure can vary depending on how it is installed. A valvespring's rate is stated in pounds per inch (lb/in), not psi as is often mistakenly applied. But most importantly, so that the valvespring works in direct harmony with the camshaft, it is critical that the valvesprings are installed and matched to the camshaft design (profile) and intended engine operation.Each valvespring (fitted with a retainer and keeper) acts to produce constant pressure to draw the valve closed so that it fits tightly against the seat in the combustion chamber. As the engine operates, the valve lifter moves over the nose of the cam lobe, and that movement transfers up to the rocker arm to push the valve open against valvespring pressure. As the lifter travels off of the nose of the cam lobe, the valvespring closes the valve. As the engine speed increases, so does the inertia. Here the weight of the valvetrain begins to play a big role, and if the valvespring is not properly matched and installed to the application, engine power and valvetrain life may suffer. Valve float may occur (even from 3,000 rpm and beyond) as the valve bounces off of the seat upon closing. Because of this, high-dollar race engines often utilize valvetrain components made from weight-saving titanium. To avoid this pitfall, do your homework, choose the right valve springs (typically recom-mended by the cam manufacturer), and install them correctly. Your engine will reap the benefits.

The Spring Opening
The valvespring's open pressure is the pressure measured against the retainer when the valve is at its maximum open point, and it is a function of seat pressure, net valve lift, and spring rate. We can determine the open load pressure if we know the rate and the installed height load. To demonstrate this, we'll use a seat pressure of 115 pounds, a rate of 400 lb/in, and 0.500-inch lift. Now, we add one-half of the spring rate to the seat pressure (200 + 115 = 315 pounds of open pressure). The proper amount of open pressure is required to control the valve lifter as it runs up the opening ramp of the camshaft lobe and quickly travels over the nose of the cam, which causes the valve to move in the opposite direction. If valvespring pressure is insufficient here, valve float may occur and reduce camshaft life as well as upper-rpm performance. Also, excess open pressure may reduce the life of the camshaft. Additionally, as valvesprings age (even if the engine is not being operated) their pressure and performance may be lost.

A stock Chevy small-block valvespring typically uses a valvespring that measures 1.250 inches across. Most performance small-block Chevy heads use a valve-spring with an OD of 1.450 or 1.550 inches. Another benefit of a larger valvespring diameter is that it may allow for larger wire diameters and the added space needed to run an inner valvespring (dual springs). Some single-valvespring setups (typically found on low-performance applications) incorporate an inner valvespring (ribbon), a flat wire that serves to dampen the valvespring's natural frequency that develops at certain engine speeds.

Installed Height
A valvespring's installed height is the dis-tance (measured with the valve closed) from the bottom of the outer edge of the valvespring retainer (where the outer valvespring locates to the spring pocket in the cylinder head). Two simple methods of shortening a valvespring's installed height are a shim in the spring pocket below the valvespring, or using a different type valvespring retainer. Retainers that incorporate a deeper dish will provide added installed height; a shallower dish, less installed height. Another option is to use a valve lock made to change where the retainer is held on the valve stem. The installed height affects what the valvespring tension will be. To see what your valvespring's installed height should be, consult your cam card. And remember that all valvesprings should be checked at a given height to be certain that the spring pressures are equal.

After the valvesprings have been installed, it is essential to check for coil bind. This occurs when the valvespring is compressed so far that its coils touch one another and the spring bottoms out. To measure for coil bind, install the retainer in the valvespring, compress the spring until it coil binds, and then measure from the bottom side of the retainer to the bottom of the spring. This dimension is the coil-bind height and can be measured on the cylinder head with a spring compression tool. With the valve fully open there must be at least 0.050-inch clearance between the coils of the inner and outer springs. This equates to about 0.010 inch between each of the active coils.

Another way to perform this test is by taking the valvespring (off the engine) and compressing it in a vise until it bottoms out. Now measure the height of the valvespring in the vise. The minimum clearance will be just enough to insert a 0.010-inch feeler gauge between each of the active coils. Assume we have an installed height of 1.700 inches with a valvespring that coil binds at 1.100 inches. If we subtract the coil-bind height from the installed height we have 0.600 inch (1.700 - 1.100 = 0.600 inch). Now subtract our 0.050 minimum clearance to get a maximum lift allowance of 0.550 inch. However, running a valvespring this close will be hard on it, so in this example we might even want to add another 0.050-inch clearance limiting our maximum cam lift to 0.500 inch (0.550 - 0.050 = 0.500). If we wanted to run more lift (above 0.500 inch) we could replace either the retainer or the valve to gain more installed height, change to a valvespring that will allow more lift, or machine the spring seat for extra depth.

Conclusion
If you want to make sure that your next engine is making all the power you paid for, don't forget to spend the time to check your valvetrain. Equally as important is that you select and install the valvesprings per the cam manufacturer's recommen-dations. A little time spent here will pay big dividends in the power game.

Valve Float causes* Valvetrain too heavy for the valvesprings
* Worn or weak valve-springs
* Valvesprings mismatched to camshaft profile
* A high rocker-arm ratio that produces excessive valve accelerations



Read more: http://www.chevyhiperformance.com/techarticles/0508ch_valvesprings_guide/viewall.html#ixzz2OrlDJWhh

02-07-2013
Supertech Valve Tech

STAINLESS STEEL ALLOYS:
Made as a one piece forged valve for higher strength and reliability.
We use mostly EV8 (21-4N) for Intake and Exhaust valves but there are other alloys that we use along with different heat treatments to manufacture valves for different applications.
Other hard metal alloys may be welded to harden certain areas like the tips or seats.
We use mainly two different type of coatings:

CHROME COATING:
Widely used in high performance valves.

BLACK NITRIDE:
This is a hardening treatment that even though it is not widely used as the chrome coating, it has several benefits and is becoming very popular, mainly for European and Japanese applications.


The microhardness is higher than the stainless steel base material, keeping good ductility beneath the hard nitrided layer (microhardness is 800HV minimum).
Surface finish is smoother than with chromed stems, having less friction between stem and guide.


Valve seat surface is harder with the nitrided layer, lasting longer with lead free fuels, alcohols, nitro or other "explosive" mixes. Matches any kind of seats (nodular iron seats, steel powder metal seats, hard aluminum-copper seats or beryllium copper seats).


Higher rpm's engines take full advantage of all previous features. The higher the engine speed the bigger the power loss due to internal engine friction! The black nitride layer reduces this power loss due to less valve-guide friction.


The nitrided layer is adhered to the base material at a microscopic level, so does not "flake" or break when the valves bend due to impacts with the pistons.


The Black Nitride applies to the whole valve while the chrome coating is only applied to the stem.


All valves are swirl polished, have stem undercut and a hardened tip.

01-23-2013
Tuesday Ten: Norris Prayoonto

You can’t go to any large Sport Compact drag racing event without feeling the presence of this Tuesday Ten interviewee. He brings a lot to the table every time he comes to compete for his team, fans, rivals and sponsors.

Thanks for your time Norris Prayoonto.

#1 – What keeps you busy? Daily activities? Normal work schedule? What does a day in the life of Norris Prayoonto look like?

My mornings are mostly taking care of my newborn son until about 10 or 11, then off to the shop. At the shop we are there every day working on our race cars and/or customers motors. My duties are to make sure everything is done on time whether it’s ordering parts for us or our customers. After that I spend a lot of time in THE room. In this room, I’m finding new things to test on the dyno. It doesn’t matter if it’s one or two hp. At the end of the day it all adds up. Oh these so called one or two hp is expensive I’ll tell you! But that’s just the way things are at the level we are at! The rest of my days are answering emails and communicating with sponsors.

#2 – Just like everyone else I assume that you have plans of making moves and doing big things in 2013. What can we expect to see from Norris Prayoonto and the Prayoonto Racing Camp?

Every year it’s the same goal and it’s to rule the world! Lol. Just taking it day by day and try to go faster and produce more parts for the public from what we have tested to work on our race cars.

#3 – Sport Compact Racing pulses through your veins as you have been doing this for so long. How do you see the next couple of years shaping up for the sport and industry as a whole? What can be done better now to aid in the continued growth of Sport Compact Drag Racing?

People need to stop complaining and be thankful on what we have today. I used to be one of those guys complaining about this and that. But now that I look back on it, I shouldn’t have. Complaining does nothing for the sport; it just makes drama and makes us look bad for the people who would like to be involved with us.

#4 – Your ability to field top level race cars and have great corporate partnerships to help campaign them is the most impressive in the sport compact industry. What do you credit your ability to have maintained these partnerships year in and year out?

In the past 9 years I have been backed by great manufactures in our industry. The main thing is I do what I tell them I am going to do. I make them look good and bring business to the table, that’s what really matters. Is what we can do for them and not what they can do for us. That’s my model!

#5 – If you didn’t have such a great partnership support system would you still push as hard to campaign the amount of cars that you do at the level that you do?

Racing used to be a hobby, it’s now my profession. If I didn’t have such great backing I would do it more on a lower scale and definitely not 4 cars. 4 cars takes a lot. Ask you yourself, what you would do if you had to do what you do now with one race car x4! It sounds impossible. But it all comes down to getting the job done and dedication.

#6 – You are one of the master minds of FTW fuel. There is much controversy over the fuel, what it contains, how it makes the power it can. What is your take on the discussions that both the racers have amongst themselves and the sanctioning bodies have regarding the legality and future of the fuel?

This fuel isn’t for everybody. It’s for the people who have spent tons of money on their race cars and are looking for more hp, without having to spend $1000s more! The fuel is 110% legal. I make sure all the fuels are within .1 percent of each other before it leaves the door. This year we are looking to expand the FTW Company into other fuel mixtures including racing gasolines. Stay tuned on this!

#7 – What are the long term goals when it comes to your business actives? What are you doing to ensure that you meet these goals and continue to push forward?

My goal is to have people realize who is the best out there. At WORLD CUP FINALS we secured 3 records in 3 classes. That was a goal I was hoping for a very long time and it happened. People need to realize our motor programs and setups are available to the public, it’s not a secret. People who follow me on social media know! We are always promoting what we do and what we have.

#8 – Racing has always been a family affair for you. We all know how much time this passion takes. Would you be able to have the committed racing program that you have if you didn’t have the support of your family?

With such a big team like I have now, family plays a big role. My dad helps me out a lot in the past 10 years. Loan my wife, has backed me since the day she met me. She even offered to learn the ways of my life in racing and look at her today! I think in any sport we need family love to keep pushing you to work hard. That’s just the nature of life.

#9 — What are your off the track and non-business hour hobbies and passions?

To be honest my life is racing and spending time with my newborn. Just as much as I want to do other things, the family and my business is what’s important to me right now. Hard to venture off to other things.

#10 – Everyone loves to learn new unknown things about a person. Tell us something that we don’t know about Norris Prayoonto?

Ummm… Let’s just say I love music and remixing them. LOL That’s all I’ll say.

09-12-2012
Supertech Engine Valve Technology

We apply more than 30 years of experience in the development of each and every Supertech racing valve we sell. Combine this experience with state of the art equipment such as ultrasonic tests, x-rays, laser measurement equipment, and applications like computerized Finite Element Analysis (FEA) and it is no wonder why supertech has some of the best performance products on the market. 

While this is more than most manufacturers we don’t stop there. We also do extensive testing working very closely with many of today's top engine builders in order to  continuously improve our products. All of this is meant to insure Supertech's industry leading reputation for high flow rates, durability and uncompromising quality.

Higher Flow Rates Our valves are not finished from generic blanks rather they are specifically designed for each and every application. We work relentlessly, testing and researching every aspect trying to improve the air flow of our designs.

Durability With every valve design we strive to maximize durability through higher fatigue resistance and tensile strength. Each valve tip is hardened beyond 52HRc.

Stem Super finishing In 2006 we introduced our stem Superfinishing as a standard addition to all of our valves and provided it at no additional cost. When our Superfinish is combined with our Black Nitrided valve it reduces the surface roughness to 1/3 of our chrome coated valve. The end result… unsurpassed performance and durability.

Strict Dimensional Tolerances It's unlikely you will find any of our competitor’s valves with stricter dimensional tolerances than our Supertech valves. Combine that with finished seats with equally strict run out tolerances and you won’t find a better sealing, better performing and easier to install solution anywhere!



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