Skimming the head

[Johnnyg]

I'm thinking of skimming he head to increase the compression ratio, but was unsure how to calculate how much material can be removed

[Johnnyg]

I'm thinking of skimming he head to increase the compression ratio, but was unsure how to calculate how much material can be removed

[Perry Harrington]

Most manufacturers in the auto world publish a specification saying how many thou per CC flat milled and angle milled.

Regardless, the amount you remove is going to be equivelent to removing that amount from the head gasket thickness. Then it becomes a simple cylinder volume calculation.

For instance, on a Ford, .040 x 4.100 is a common head gasket size for the SBF. You can get various smaller gaskets, such as .038 and .020.

On a bike engine, milling the head will make very little difference to the CR because the cylinder is so small (on most 4 bangers). On thumpers it's different, with the WR450 having a 95mm bore.

You'd have to deck the block and mill the head to make a substantial volume difference. However, CR is also the difference in compressed volume to uncompressed, so you are doubly affecting the CR by milling.

--Perry

[DaveC]

This has been beaten to death. Search (wheres the :flipoff: smiley when you need it?)