Hello All,
Well big bore build did not last long. Started up well, two heat cycles to set rings, then at the track exhaust overheated the top of the new piston right off. No clear root cause. Fuel/oil and jetting was good.
Symptoms.
1. Top of head bolts were leaking coolant after first hot laps ( 5 laps).
not using stock acorn cap style head bolts.Motor temp was reaching operation temp more quickly then in the past. ( up to 150F very quickly!! This is your first clue Mr. Dumbass)
2. Torque of head bolts originally set to 18 lbs then went up to 22 lbs. ( Stopped coolant leak for next heat race.)
3. During that race notice lack of smoke out the tail pipe. (Driver does not know) Within 3 laps it was all over. Motor loss power and over heated, was very hot (190F - 200F) and leaking more coolant out of top of head bolts.
Recover:
NA, cylinder wall is scored and can't bore any larger due to power valve interference. Cylinder needs a new sleeve.
Our guess is if the head bolts were leaking coolant then it very well have been sucking air also, made a lean condition and over heated. However: confused by why only exhaust side of piston melted down, Intake side looks well. ? &*^%???
Any suggestions out there?
Lesson learned.
Use new stud bolts when in doubt, use quality gaskets, ( Cometic from now on, not moose fiber) when there is a coolant leak and reaching temp quickly you have a larger problem than you think.
Thanks