I checked and got 28cc in both heads so DD would be spot on cause both heads have been shaved.

What purpose? The open chamber is to reduce nitrous oxides, not to lower the compression. For the high-comp GX they used flat-tops pistons instead of dished pistons.

For the Datsun 1200, open and closed chamber heads are the same CCs aren't they? 29.3 ccs. I could be wrong.

Why don't you measure the chambers of your head and tell us what they are. I don't have an A14 head or I'd do it.

wouldent that defeat the purpose? wether that purpse be economy or power?

I thought open and closed chambers have the same CCs?

I think they came with difernt dish pistons achieving the same comp.

I thought this was a lower comp head?

Oh the H75 doesn't have the quench chamber. It'll run OK but it's not the optimum power. It's the only kind we got here in USA (we didn't get any closed chamber heads expect 1971 A12).

Either way, it's the same compression ratio as closed chamber heads.

H75 head slightly ported to match GX manfold (NZ GX).

Attach file:

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  H75 head 1.JPG (71.49 KB)


  H75 head 2.JPG (83.46 KB)

H75 heads have open chambers ports are of the low variety I think
don't look as open as the pics above
check my build thread for some average pics of a h75

First post on my new iPod touch what a cool freAking device

What version of the A12 are you using, & this is important.
If you are using the 1970 to '73 1200 engine, then you will need a modification to use the A15 head to allow oil to reach the rockers.

If you are using a 1974 or later engine with the set-back distributor, then just bolt it on.