Sooo, car was fine with 178k miles. Was driving it last fall up a long freeway climb, steady power, consistent RPMs, all was well. Felt engine kind of go off song. It started to lose RPMs, temp normal, power dropped off, saw smoke in the rear view, let off worked over from #1 lane to shoulder. Temp had begun climbing quickly. By the time I pulled over the engine wouldn't idle. Died.
Got it to the shop next day, they said HG, coolant in the #4 cylinder, $3k to repair. I said no thanks. Threw it on the side of the house and forgot it for awhile.
In the last month or so got motivated to replace it, seemed like a big, but not overwhelming task. I used to race karts, did my own engine work on those, and have built a handful of engines, set up differentials and even a couple of transmissions.
Via a poorly titled thread, I've used your help to yank the head, pull the cams, remove the valves, clean up the head, prep for reassembly and reinstallation.
I found the gasket remarkably intact, had expected a "blown" hg to be self evident. It was not. Expected the head to have problems, none. It's flat to within .002" in every direction, no cracks, valves and seats look good.
Today I went to clean up the block deck and my heart dropped. Partly because of the gravity of the situation and partly because I'm disappointed I didn't see the damage earlier.
Aaaaagh!!!
The cylinder walls of #3, #4 and #5 where the 3 cylinders adjoin look scorched from overheating and lightly scored. There appears to be some aluminum transfer from the pistons, but only at the very top of the cylinder above the ring level.
When racing a kart and letting the motor get too hot, many a karter "stuck" a piston. In those cases the piston would stick in the bore and the aluminum transfer would be in the middle of the stroke. We'd use acid to remove the aluminum, hone the bore, drop in a new piston and ring and be on our way.
This seems more mild than that and concentrated to the tops of the adjoining cylinders.
Any guesses on what transpired? How did just those areas get so hot?
What would you do in this situation?
Replacement engine time?
Hone and rings?
Other?