ok next question, i think i know the answer but just to check what you guys think....

See the picture, the Mazda piston has a cut out one one side, i assume this is for valve relief with the std mazda head.
if you install the pistons with the 'F' to the front (as i have done so far) then the cut out is on the side of the engine with the spark plugs, and with the H89 head where the Quench is.

Would it be better to install the pistons backwards? so the quench portion of the head is presented with a flat part of the piston and the cut out goes on the other side ?

That is my thinking.. the 'F' is just an aid to people rebuilding a std engine...

pretty important to decide before i start to cut the valve reliefs.....

EDIT... my bad, im getting confused with seeing the head upside down.. pistons should be fitted with the F to front as this aligns the flat part with the squish correctly.

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  mazda UC piston cutout.jpg (98.90 KB)