Cams determine the characteristics of an engine. If you know the intended use of
an engine you can quickly determine the cam that should be used. You must be
realistic. If you are looking for maximum acceleration, you won't be able to drive
that engine on the street. For example, maximum acceleration means a fuel other than
gasoline, Alternative fuels mean extremely high compression. Exotic fuels are
simply not appropriate for street use.
Speed is money how fast do you want to go? Determine how much you want to spend
on an engine. With that information you can then determine which cam you need.
As an example consider a US made V-8 of about 5 to 6 litres displacement.
Up to $3,000 - That's a total investment. An engine with less than $3,000
invested will probably have an OEM crank, stock rods and stock heads. That type of
engine is not suitable for high RPM use, so you need a hydraulic cam with a torque peak at
about 4,500 RPM and redline of about 6,500 RPM. If the engine was originally
equipped with a roller cam then by all means retain the roller setup. A hydraulic cam is
excellent for this type application. A dual plane intake manifold and stock or small
tubular headders are appropriate. If the rear end ratio is changed it probably will
be 4.11 or less (numeric.) Horsepower output will mostly be a function of the
engine.
Up to $6,000 - Now we're talking about an improved crank, pistons, and rods.
Probably there will be a set of aftermarket heads. An inproved
valvetrain will also be affordable. The RPM range will be 7,000 RPM and above. A 180
degree intake manifold is the best choice for induction. Large diameter headers are
most effective. A light car might not need more than two speeds. A high stall
speed converter is indicated. A solid lifter cam is appropriate at these power
levels and a roller cam is not too much to expect.
Over $6,000 - This is all out roller cam terrority. As before, the cam should be
inline with engine modifications. High speed is the thing and 9,000 RPM engines are
not uncommon at the more expensive levels. All out racing cranks with extra large
fillets and other strength features are needed along with special rods and pistons.
No head is too good for such an engine and the more air flowed the better.
Two carburetors are appropriate to an engine like this. There is not much of
a cam difference between over and under $6,000 but valve train components such as valves,
rocker arms, keepers and pushrods are more exotic and expensive.
To sum up, the steps of cam evolution are hydraulic, solid, hydraulic roller and solid
roller. The technology is determined by other engine components. The final cam
choice might be between a number of grinds. Professional racers find that traction,
temperature and similar concerns can change the best running cam, with no other changes.
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Competition Cam camshafts
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Crane Cams
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