Blew the hell out of my headgasket earlier this week (t-stat stuck about 1/16" open and overheated). I straight edged everything and it looked good. This is a freshly built Z6 with forged internals and I have barely 450 miles on it. Z6 block D15B head/cam with Wiseco 75.5mm 8.5:1pistons on eagle rods. Opinions on these numbers?

175
165
170
160

I did the test twice and came up with the same results both times. I am not new to this but am new to low compression engines. The numbers are within 10-15% of eachother but a variation of 15psi has me a bit concerned. I recall my 75k milke D15B had 190psi on all 4 using the same guage. Could it possibly be due to being relativly new and not fully broken in yet? Opinions, comments and knowledge welcome. This was a dry test and I did it hot after a few hot and cold cycles.

 

first of all 8.5 compression gives about 170 so u should be good
and secondly on the last few hgs ive replaced it had taken a couple heat cycles for the gasket to fully seal

redo the test in a week