I've searched the forum and couldn't find an answer to my question:



Due to the irregular shape of the head gasket bore opening can someone tell me the correct diameter to enter into the compression ratio calculation formula? I measured the length of the opening with a piece of string and it is 13 5/16". If this was considered to be the circumference of a circle, the diameter would be 4.237". But is an irregular shape treated differently. I just barely scraped through geometry in H.S. and that was a long time ago!!! Thanks.








FIGHT CONFORMITY! 

Once you find the theoretical diameter by measuring the circumference of the irregular sized hole, the rest of the calculation is treated like a circle.  You didn’t mention the gasket thickness, but with a 4.237” diameter hole and a 0.041” thick gasket, head gasket cc’s will be 9.47cc’s.

 

Here’s the calculation.

(4.237) X (4.237) X (0.041") X (12.87) = 9.47cc

Lorena, Texas (South of Waco)