Hey ddgonzal, Ive got a h75 head which looks like its got great open chambers for turboing... would this be correct? am I going down the right path here?
cheers.
Adam.

The open chamber heads are not any lesser compression. Not sure if they'd be better for turbo or not.

With factory A-series engines, the compression is controlled mostly by the piston dish.

gx1200, use a h89 head or shave your h75 to make it
a close chamber kidney shape & use e15et dished pistons.
Open chamber heads where mainly for poor fuel quality.

mainly for poor fuel quality and for lower NOx emission i guess?

My h89 has 24cc chambers

Is your H89 head factory-stock, or has it been ported?

Yes, open chamber is for lower NOx emission. Not anything to do with fuel quality. For lower octane fuel they make the compression ratio a little smaller, like 9:1 instead of 10:1 which calls for high-grade fuel.

Interesting that it will get better Nox ratings
I thought closed chamber heads have much better
Nox ratings due to efficiency.

NOx emissions are related to combustion temperatures and the fuel mix.

A very poor low Nox design compared to the Z series
pro swirl open chamber dual spark heads :)
Either way the h75 is not a good performance choice unless
its milled for gx1200`s turbo setup.

That was was I had been planning to use for an A14 turbo. Those e15et pistons have a MONSTER dish. My concern was though that having the H75 head shaved that much could create valve to piston issues wheh run in conjunction with a monster cam. (I was planning to zero deck the block as well) Baring in mind that the E15et chamber is something like 18cc. (Thats a lot of meat to shave off an A sereis head)