Thanks heeps tsillay!! thats exactly what I needed to know.
One more question; is the a14GX head any different than a oval port a15 head?
cheers
Quinn

ps ddgonzal I plan to take the lot. I can start the 1200 with a spoon handle. not so safe.

The difference, if any must be subtle!
I did once find a factory A14gx with twin hitachi SU's which had flat top pistons and huge combustion chambers in the head. This head wasnt up to much!
I swapped the head for a normal A14 oval port one, popped on a pair of 40 dellortos and headers and the thing simply flew!
It was in a coupe, with the dogleg 5 speed and some kyb shocks... To this day that's the most fun road car I've ever had....

Usually ...

A14 "GX" = high compression
A15 normal = low compression

But there might be variations, as Tsillay found.

Ive taken the head off and using a syringe (very teco) I mesured the chambers in the head

A14 = 30cc
A12 = 27cc

this is a bit rough as I was holding the heads level and porring at the same time but it pretty close i think. The a14 comes with dished pistons where as the a12 comes with flats tops (or has my coupe got aftermarket ones?).
But according to some info I found on the a series all three have the same compression ratios. maby the a12 dosent have a full stroke?

GX engine has higher compression, but was a Japan-only engine.

mmm, so very roughly, if you say an A14 cylander holds 350cc, + say 4cc for a headgasket

354/34 = a C/R of 10.4:1 with a flat top piston....
Which would be bloody fabulous for a hot road motor, that sorta compression would make a fast road/rally cam light up beautifully..

Mitsi Galant (1750?) pistons work, they're 79mm and more or less flat topped...I hear good things about the mazda ones too...