Does anyone on here actually know how all of this is calculated? What parts in a motor to replace to actally get some gains? Im just interested to know a bit further on how this stuff is calulated. For example if you replace a gsr head with a type r head on a B18C1 does this increase compression and why does it increase it? what parts make it increase? what's an example of higher compression, is 11:1 higher than 8:1? Thanx to anyone who can answer these for me.

 

11:1 is higher than 8:1. In order to raise compression, you decrease the size of the combustion chamber relative to the displacement. You can do this by milling the head, installing domed pistons, welding material to the head, etc...

I don't think there's a simple formula to claculate how compression affects horsepower/ torque. A complex formula could probably be derived from extensive tests on various motors. I guess its accepted though, that a point increase in compression (from 8:1 to 9:1, for example) would net a 4% increase. I doubt this is accurate except maybe over a narrow range of compressions, and only with certain motors.

Horsepower = Torque (lb-ft) x RPM/ 5252