The HD maintenance manual publish the 103 compression ratio at 9.6-1. Does anyone know what the installation of the 0.30 cometics head gasket will increase this to?

 

Whats the stock head gasket thickness?

If you know that then it is easy to work out the change in volumes and the new comp ratio.

 

I'll take a stab a this since no one has come in. I THINK the OEM head gasket is 0.040 or 0.045. If it's 0.045 and you want to run a 0.030 gasket your effectively taking 15 thou off the head.

I THINK you would be around say 9.8-1 or 9.9-1 but it's very approximate. I hope someone comes in with the knowledge to assist more accurately.

 

I found a calculator on big boyz web page that actually takes the cam info into consideration also. Static they said approximately 10.2ish correct with cams varies from 9.3 to 9.9. Don't really understand it all but the cam I am looking at is for 9.5 to 10.5 so I guess I will be good! Thinking about the HQ575H
thanks.

 

..static refers to the engine being turned over, but not firing..compression is a little lower when you have the engine running...