In part 2, we discussed how family characteristics would make an engine react differently to modifications. As an introduction to this part, we will go back to 1970 to review two road tests in the April, 1970 issue of “Car Life” magazine. These tests show how engines from the same manufacturer react with “high performance” modifications. “Car Life” tested two new GTO’s; One was a Ram Air 400 rated at 366 HP @ 5100, 445 ~ torque @ 3600, with 4 speed, 4.10 gear, PS, and PB. The other was a 455 rated at 360 HP @ 4300, 500 # torque @ 2700, with automatic, 3.55 gear, PS, PB, and air conditioning. Following are some pertinent excerpts from the “Car Life” article pertaining to the engines/performance of each. Read more

Static compression, (C.R.) on a Pontiac is a function of the chamber volume and the engine displacement. If the chamber volume is increased, the C.R. goes down; if the displacement is increased, the C.R. goes up.

Following is a listing of the chamber volume in cubic centimeters (cc) of selected Pontiac heads used from 1966 to 1979. Read more

I’m always trying to improve the quarter-mile performance of my 1971 455 LeMans wagon, while retaining derivability, a 3.55:1 axle ratio, and a 5,500-rpm shift point. I recently tried several custom-ground cams, and I want to share the results with you. Read more

We have found that certain modifications to the rear suspension on all A Body cars will cause wheel hop during hard acceleration. The use of air shocks or booster shocks (small springs mounted around the shocks) will almost always cause a wheel hop problem. These two devices keep the rear axle assembly from rotating through its normal arc under acceleration. The result is wheel bounce, and if not stopped immediately, broken transmission cases, U-joints, or rear axle assemblies can be expected. Read more

We often read and hear about “adjusting” rocker arms for more performance. How is it done and what actually is accomplished by adjusting rockers? A quick description of the valve train will help clarify the operation. Read more

Note: This article has been published several times in various forms. This slightly revised version is for those that have not seen previous versions. This article is oriented towards drag racing. However, it is generally applicable to all cars.

FRICTION MATERIALS:

Asbestos, the cause of many health problems around the world, is also the cause of many of our brake problems. The health risk from asbestos in brake friction materials has spurred the development of replacement materials. Unfortunately, although some of the new materials are superior in many ways, none of them provide equal friction coefficient as asbestos at the same application pressure. Therein lies our problem. Read more

The Q-Jet intake manifolds from 1967 to 1972 are functionally equivalent (except for type of chokes) and will bolt up to any 1965 and up heads and front cover. The 1973/74 manifolds are similar in function (and will bolt up) but have the EGR provision which requires a matching push rod cover (1973 to 1979). The 1975 and later Q-Jet manifolds have the EGR, restricted secondary openings, and poorer overall design. Read more

The harmonic balancer is installed on the front of the crankshaft primarily to dampen the torsional vibrations of the crankshaft that is caused by the power pulses of each cylinder/rod. The secondary purposes of the balancer are to provide an ignition timing mark as well as a mounting point for the various drive pulleys. Read more

A cooling system consists of: The radiator, radiator cap, overflow tank, water pump, thermostat, fan assembly, fan shroud, hoses and the coolant. (The water passages inside the engine block technically are part of the system, but other than cleaning them during an engine overhaul, there is no practical method of changing their operation.) Read more

The most significant advantage of tube headers (with a common collector) is their ability to lower the atmospheric pressure within the collector. This provides scavenging of the combustion chamber, which more effectively removes the exhaust gases and tends to “suck” the intake charge into the chamber during overlap. The effectiveness of the scavenging is dependent on proper matching (tuning) of the header pipe sizes to the engine RPM and application. Read more