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Frequently Asked Questions (FAQs)

PMS Frequently Asked Questions

When you specialize in building muscle car engines and rebuilding custom vintage car engines for 40+ years you tend to hear a lot of the same questions over and over.  Our FAQ page will start off with a few questions and answers, adding more as we discover the most important ones. More FAQs will be added, in hopes of answering our customers questions, as time permits.

Q. How much compression can I have in a pump gas engine?

A. In a normally aspirated engine with 93 octane ethanol enriched fuel you can safely run 9.5:1 compression with cast iron heads. An aluminum cylinder head on the same engine will allow you to run 10.2:1 safely. Ignition timing and timing curve must be precise, based on you vehicle’s weight, transmission, rear axle ratio and more. Camshaft choice is also critical.

Q. What camshaft do I need?

A. With very little exception, everybody wants to over cam their engine. The premise being, bigger is always better. The truth is, camshafts that work well for your particular application are very specific. To determine the best cam for you, vehicle weight, transmission, rear axle ratio, compression ratio, tire size and primary use of the vehicle (Race, Street, Drag Strip, Daily Driver, Mud Bogger, etc). A very large consideration is the choice of a flat tappet cam or a roller cam. A roller cam is the preferred choice, however cost is a big factor, especially in vintage engines requiring a retro kit. I always encourage my customers to go the roller route if they can afford it. Using a flat tappet cam requires the use of Nostalgia Motor Oil or a zinc phosphate additive since the EPA, in their infinite wisdom, forced the removal of zinc phosphate from motor oil. Roller Cams allow the use of asymmetrical and involute cam lobe profiles, opening and closing valves rapidly with preciseness. Comp Cams is our exclusive provider of quality custom ground roller cams for every engine application.

Q. What carburetor and intake manifold should I use?

A. Carburetor selection is based on the maximum air flow the engine will require at maximum RPM (revolutions per minute). To get this accurate is a mathematical calculation, not a guess. Your carburetor style is based on the engine’s basic use (Street, Strip, all out Drag Racing or Circle Track Racing, etc).

Intake manifolds come in many configurations single plane, dual plane, tunnel ram, high rise, medium rise and low risers, where hood clearance could be a problem. The same as compression ratios, camshafts and carburetors, intake manifolds should be selected for the primary use of the engine.