Friend had another friend build his motor (big mistake). GSR with eagle rods and j/e pistons. Stock head with vavle job. Car had a bad oil leak to begin with, but we tracked it down to one of the cam caps on the head being loose (don't ask). The problem now is oil consumption. He has about 1800 miles on the car now, and it is burning roughly 3/4 to a quart of oil a DAY! The "friend" that did the valve job on the head said they used the wrong valve stem seals. Seems like a LOT of oil to use from the head. I figure its in the bottom end. Bad hone, bad oil ring, improperly file fit oil ring, no oil ring, (with this guy, its possible). The motor made good compression, but I figure that the oil in the clyinder could have sealed it. We took the head off to have it checked. The combustion chamber was disgusting. Oil sludge everywhere. Pistons had burned oil covering them of course. Here's the wierd part. I could fit my fingernail into the gap between the piston and the cylinder wall. If you look straight down at the piston, you can see the top ring. I don't remember being able to do that on any other motor I've built. Maybe its just me, but is that ok?

 

Well forged pistons have a larger clearance the OE pistons...as they expand when they heat up...but I don't know about a fingernail width....

 

texan - yeah, that was another possible thing we thought of. That, and filing the rings too much were the first on my list. But the bore issue is weird. Anyone seen this with low compression pistons, like 9:1, or is that still too much?

 

I'd change out those valve seals again also just in case after doing them rings.

 

The old rule is that if you're blowing smoke when you decelerate it's the valve stem seals, and if you're blowing smoke when you accelerate(more likely here) then it's the rings. What type of rings were used, how was the block treated...light hone, bored what?

 

your piston to wall clearance is way off if you can fit your fingernail in there and especially if you can see your top ring. That menas the gap is WIDE OPEN too ... Best bet is get next sixe over piston, so if you're at 81mm and can fit you fingernal, maybe they bored it 81.25 if not open it to 81.25mm and get pistons to fit that bore. Or just go with Endyn 81.5mm pistons and over the bore up.

Greg


Greg

 

Does sound like a bit much, even if your pistons have a very low silicon content and are designed to expand significantly.

 

if the block was not bored then you may need to do this, after a period of time the bores end up egg shaped from the stroke of the pistons. this would be my guess after you check the valve stem seals