[bmalone]

The SOHC project initially had two specific goals. One to utilize as many components as prctical from the 427 wedge motor, and two to develop enough additional HP beyond the wedge motor to make undertaking the project practical--without significant extra cost and re-tooling.

Thus, the run of crate motors planned to use iron heads. Aluminum heads were made later for specific purposes and yes, they are much rarer. I have heard the breakdown is 70/30.

Aftermarket pistons are available that bring compression down to a 11.0:1 range. That is where my motor is at. I will soon find out if that is accurate and how it behaves on the street. I do plan to use race gas.

More interesting tidbits: Series 1 and Series 2 motors. Series 1 had the exhaust valve offset from centerline and the spark plug was roughly in the center of the chamber. Series 1 had single 4 intake, which at sustained high rpm produced lean condition to center four cylinders, where the bend of the runners was 90 degrees. Also had non-adjustable rocker arms.

Series 2 brought the exhaust valve to horizontal centerline and plug was moved more to the intake side of the chamber. 2x4 became the standard intake--runners were shorter with very little bends and this produced a ton of HP. Adjustable rockers.