A question for engine builders: What thickness of head gasket, and what piston will yield 10:1 compression when building a Twin Cam 96 into a 107?

 

PMCBURNE,
There are a number of things that you want to consider first in order to achieve your goal of 10:1 CR
1) Compustion chamber volume in CC's
2) Cylinder volume in CC's
3) (Compustion chamber Volume + Cylinder volume) divided by combustion chamber volume = compression ratio.

That is a basic formula.

A more advanced formula uses head gasket thickness measured in CC's, but where you piston is sitting at TDC is critical too. If you go too thin you run the risk of pounding your piston into the bottom of the head at high RPM's. The safe gap in the squish area is .035. There is a method to measuring this without having the heads on and torqued down.

Some pistons at TDC are at the top of the cylinder and some are roughly .015 above the top of the cylinder and again some are below the top of the cylinder.

If you use a squish gap of more than .045, you run the risk of having detenation issues, because carbon will build up in this area and carbon holds heat like glowing charcoals.

 

PM sent

 

thanks for the info

 

You may find the calculator from BigBoyz helpful:

http://www.bigboyzcycles.com/TwinCamComp.htm

Carl

 

excellent. Thank a lot