Modifying an engine, be it a complete assembly or a bare block, requires experience and know-how. If you don’t know, ask someone who does. Increasing the compression ratio (CR) is often one of the first engine performance modifications. Squeezing the air-fuel mixture into a smaller space increases its temperature and ease of ignition; thus the rate at which heat is extracted from the fuel. Engineers call it “thermal efficiency.” Simply put, it means that increasing the compression ratio increases horsepower.
Henry Ford’s Model “T” has a CR of 3.6:1. High performance engines operate in the area of 12.5:1. Most of today’s stock production engines are about 8.5:1. FORD RACING CAMSHAFT USAGE The durations shown in this chart are S.A.E. durations.
