Combustiom chamber vs compression ratio

[DAVID GAGNARD]

Galaxy;

You do not need to change the heads,you could simply cut (shave/mill) the heads down to the desired cc's.... Most closed chamber heads go like this, for every .006 you shave off the head you lose 1cc in the combustion chamber....You would have to calculate how much you would need to get from 9.5 to 1 to 10 to 1....You will also need to check for valve clearance....I would not cut more than .020 but it depends on the heads you are using... .020 would take the 65cc heads to approx.. 62cc and raise your compression some.....

Performance on a 58 cc head vs. a 65cc head assuming all other things being equal should only amount to the increased compression and corresponding increase of hp by the increased compression....

Another way to raise compression cheaply is decking or cutting the top of the block. First install the crank and a couple of pistons and measure the piston height at top dead center,I've seen some pistons as low as .075 from the factory,then you can determine how much you could deck the block down to without the pistons popping out of the block....

David