Lean, or excessively retarded timing will do it too.

What would be excessively retarded? I had it at 32-34* all in. I want to say it was 34 but might have went 32.

That's not excessive.

Oil therm , block bypass to therm housing, take valve out of thermostat , #10 lines,big coolers , transom water pick ups
New strainers, bravo pumps, keep block pressure 25 psi or less. Let er rip

I run 34 degrees timing and a conservative 650

Is that supercharged or NA?

Cause of engine damage has been discovered. When I brought the heads in, my guy said the motor went lean. The beating the bearings took also suggested the motor went lean and detonated. Well Here my friends is the answer. The most expensive vacuum cap ever!!

No pun intended but.... THAT SUCKS!!

Ouch!

Yup. I put new head gaskets in the motor 50hours ago. The motor looked good inside at that time. I only pulled the motor to switch to inconel valves. I wonder how long I had been running like that.