I did a total rebuild on my motor, new bearings, bigbore kit the lot. Even a totally new head.

It ran great and made good power (93bhp at the wheel), but started burning oil. Strange though as the smoke was black, not blue. Anyway I was on track and got told a few times people could see puffs of smoke. Last session out I get black flagged for smoke, I check the oil and it's gone from max to empty in one session (we were checking it all the time).

After testing the motor and now a strip down i'm pretty sure it was the valve guid seals. I used a cheapo replacement set that came in one of those ebay gasket kits.

first off i thought it was just cheap seals, but i measured the valve guide projection this time (i.e. how far they had been pressed into the head) which was the only thing i didnt measure when i built the motor up. Quite a few of the guides arn't pressed in enough, with two of the worst being about 0.25mm too far out of the head.

My question is, is 0.25mm enough for the valve keeper to tap the seal and cause it to fail? I'm running standard cams.

thanks in advance

Phil

p.s. this is it:


other side: