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 Your camshaft selection will be one of the most important
purchases
The camshaft acts as a "traffic cop" in your engine. It is there to make sure the valves and pistons do their jobs as efficiently as possible, but at the same time never make contact with each other. In simple terms, a camshaft's lift determines how far the valve rises from its valve seat.The lift has a dramatic effect on low R.P.M. performance, but has a lesser effect at higher R.P.M.'s Duration is also important. If you looked at a long duration you would notice that it is wide and blunt. This enables the valve to stay open for a longer time or duration. Duration has the opposite effect of lift. The longer the duration the more the higher R.P.M. horsepower will be boosted, however, at the expense of lower R.P.M. horsepower. The lobe centers of your camshaft are very important, but often not discussed. The lobe centers of a camshaft are the placement of the intake lobes in relation to the exhaust lobes. Example: you can't put an early "S" cam in a C.I.S. or turbo engine, because in a C.I.S. engine, the fuel injection is regulated by the engine's vacuum which draws air into the engine. When the lobe center is at 113 degrees, which C.I.S. cams are, the intake and exhaust valves are not open at the same time under most R.P.M. conditions. If they were the resulting condition would be called "overlap" of the valves. When there is a lot of "overlap", the vacuum of the engine drops dramatically! This makes the C.I.S. injection lose its controlling feature. Turbos have very little overlap because under "boost" conditions the pressure generated by the turbo would be blown out through the exhaust valve during the overlap. On carburetored engines there are no vacuum problems, except that sometimes power brakes don't have enough vacuum. An example of a high overlap or lobe center is an early "S". It has 97 degree lobe centers. At most R.P.M. ranges , intake and exhaust valves are open at the same time for a split second. Notice "hot rods" and other engines with a single carburetor. At idle there are exhaust gases contaminating the fuel and air charge in the combustion chamber. That is why they idle so poorly. They can't adjust the fuel mixture for each cylinder as we can with our three-barrel carbs. The reason "overlap" produces horsepower is because at high R.P.M. when exhaust gases are escaping they draw or pull the intake charge into the combustion chamber for a larger volume of fuel and air. For this reason, Porsche's newer engines and others have used two camshafts on each side, one for exhaust and the other for intake. They hook up a mechanism to "vary" (as in vari-cam) the overlap at different R.P.M. This way you get the best of both worlds. As you can see, the requirements of your engine must take into account many different factors. Call us today for a complete evaluation of your requirements. Every camshaft is precision ground and polished and then "parkerized" for oil retention to assure easy break-in and longevity. You will receive cam lube and installation instructions. We recommend your rocker arms be resurfaced to remove the "glaze" on the surface of the mating surface. We can do this for you, or just follow the directions on our instruction sheet. Performance Cams for Porsche Motor Meister's Performance and Racing cams are the perfect compliment to our current stock of performance and racing line for your Porsche needs.
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Misc Camshaft parts available for Porsche motors:
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Many racing cam applications not even shown, please call for needs! |
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Is the engine to be used
for street, street and track, or track only
