81 and 84 GPZ1100 cylinder head comparisons

The j head can be used on a kz block if u add the APE cam chain adaptor. This head will drop the compresion 2 full points.
The 82/85 GPZ heads will work but u get a larger bathtub shped chamber and a 2.4 poit drop.
The Z1/KZ head has 36mm intake, 30mm exht valves, J= 37mm, xht= 31 GPZ= 38mm, xht= 32mm.
Here is APES info:
www.aperaceparts.com/tech/techkz1000.html
The GPZ head can be used with the J block but i believe u would have to change the tower to accept the dif cam chain.and adjust to corect for the .4 compresion loss.

the 81-82 gpz uses a 17mm wristpin same as the 73-80 z1 and kz also the same as 1000 j motor,while the 83-84 1100 uses 18mm wrist pins in the pistons.thats why i say stick with the 81-82 gpz or j motor head to save a lot of head scratching

heres the bath tub from the late gpz

heres an early j motor head with the hemi type combustion chamberB)

Thanks for everyones input. On second thought I'll hold off till I can find a 1982 Gpz 1100 head