Even though you have good compression you probably have a bad headgasket. Was the head machined when everything was apart for the rebuild? If not then I'd put money on the headgasket.

I recently did a head swap where I didn't machine the head, and even though I have 190 compression across the board there's a small coolant leak across the back where the head is slightly warped.

Now I get to do it again... At least I don't need to rebuild the head this time.

Erik P.
Official 2GNT thread Hijacker
Some say that he's driven over more Covenant than he's shot, and that his grenades aren't where you'd expect them to be...
All we know is, He's not The Stig... But he is The Stig's Spartan cousin!