As usual, information on these and other heads is all different from one source to another. Some say they are 64 cc chambers, others say they are 76 cc chambers, some say they have 1.94/1.50 valves, others say they have 2.02/1.60 valves, some don't list the intake runner volume, others say it is 165 cc's.

I suggest that you procure a burrette and measure the chambers and runners yourself. If you're unfamiliar with the procedure, here is a paper I wrote....
http://streetmachinesoftablerock.com...opic.php?t=124

If you find that they're 64 cc chambers, I suspect that would explain the motor spitting out the head gaskets....to high static compression ratio / deck and head not parallel / detonation from insufficient fuel quality / early intake closing point on camshaft resulting in excessive cylinder pressure for available fuel....