I just had overheating issue, did test and such, realized it was my head gasket.
I removed head and i saw something else… cylinder 4 is badly scratched, one of em is really deep. No loss of compression though, still 180 across 4.
What do you think ? Engine was rebuilt lass winter…
what is that pariculate in the cylinder? maybe your rings didn’t seat right when it was rebuilt? maybe some rust got into the cylinder through the headgasket? not much help, i know 
hey, read this. it will help you out. I don’t know if maybe your tune was off but it looks like a lean condition is/was present. that will cause your piston to wall contact. I dunno, at this point, I would tear it down again and do it right this time. can you run your fingernail over the deepest groove? if your nail catches it, then I would bore and hone to the next size…goodluck man
i think that cylinder was geting hot or the hone job was off so there wasent anuf clearence in that cylinder.check the bore or add some fuel in that hole.doesn’t look dat bad anuf for a rebuild yet.
well my fingernail can really go into that scraatch ! i will turn crankshaft it 180 degree and poor gas in it to see if it does not leak and hold the gas.
As for the tuning, i was running 10:1 for a long period because my wideband was offset by 2 points … This article was good reading !
I’ll keep you posted for the final rebuild… see ya !