Cam selection

Cams determine the characteristics of an engine.  This one component will determine the basic characteristic of an engine.  If you know the intended use of an engine you can quickly determine the cam that should be used.  First, 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, exotic fuels are simply not appropriate for street use.  Alternative fuels mean extremely high compression.  High compression and high RPM mean new crank, rods and pistons .... and so forth.  Just putting a high performance engine cam in a stock engine will cause a loss of power and disappointing results.

There is a lot to the saying "Speed is money how fast do you want to go?"  Determine how much you want to spend on an engine. That's a total investment.  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 litters displacement.

Up to $3,000 -  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.   A hydraulic cam is excellent for this type application.  A dual plane intake manifold and stock exhaust manifold 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.  NOTE: If the engine was originally equipped with a hydraulic roller cam then by all means retain the roller setup.  You can replace the stock roller cam with aftermarket and enjoy more power with the reduced friction.  A stock roller cam reduces friction and you get increased increased horsepower without fuel expense.   

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 improved 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 territory.  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.