tomcat

I have GM aluminum oval port heads with 110cc chambers. They make about 9.5:1 compression on a 502. I would like to lower the compression to at least 8.75:1 so I need to add at least 10cc. Is the oval port head cut from the same casting as the rectangular port head with its 120cc chambers? Can I get to 120cc just by removing material from the chamber? How much material is removed when unshrouding the intake valve?

Thanks

Tom

JimV

tomcat


I believe the castings are different so you would not be able to duplicate an open chamber head. You should be able to come close to an 8cc gain by unshrouding the intake and exhaust. 5 cc's is easy to get on a normal chamber port with an open chamber head. You will problaby gain more airflow on the exhaust side. Keep .040 to .050 inside the gasket near the bolt hole on the exhaust. This will help protect the gasket from heat. Airflow gains on the intake will depend on the valve size, you may see a 2-3cc increase for volume depending on how much you can lay the chamber back