Oil leak problem

[Robbo]

Hey guys. New to this forum.

My mate has a MKII Supra, 87 model I think. It has the 7MGE non-turbo engine in it. My dad is a mechanic and did some work on it. It was previously going through oil reasonably bad (Im not sure where it was leaking from at that stage). Anyway, long story short, the head has been replaced and the engine is leaking oil out of the exhaust, but there's no blue or white smoke, so we have assumed that the oiil isn't getting into the combustion chambers before going into the extractors. We're really quite stumped on what has caused this. We are trying to avoid taking the head again at this stage seeing as it is such a pain in the arse to do.

Does anyone have any ideas? Anyone been through the same dilema before?

Btw - when my father purchased the head for it he specifically asked for the non-turbo one. No worries, but we've since asked the guy we bought the head from regarding the oil leak and he is now trying to say that the Supras don't come out non-turbo. Anyway, this has made us think that maybe he sold us a turbo head. Are there any differences between non-turbo heads and turbo ones? ie. does the turbo head have different oil galleries, or don't quite line up?

Alternatively, does anyone know where I can get diagrams of the engine's oil galleries so we can check it out ourselves.

Thanks guys

[repinS]

Hmm. What I do know is that 7M-GE and 7M-GTE have different cam profiles - the turbo version has no valve overlap (favourable for a turbo setup). I can only assume putting a turbo head on will have adverse effects - is your mate's Supra down on power at all?

This thread would be better off in the hands of Bob (bgreiger) or Jeeves

[bgrieger]

Head casts are identical. Your oil problem is on of the traditional problems...valve seals/guides, or rings. RepinS is bang on that the only difference in the head was the cams, and at that I believe it is only the exhaust cam that is a different profile.

Bob

[Robbo]

Thanks guys.

If it were valve seals/guides or rings then the oil would be getting inside the combustion chambers and producing blue or white smoke, which it's not. Somehow, oil is getting from the engine into the extractors without going into the combustion chambers, and THIS is the big question mark for us.

But now that we know that the head casts are identical (thanks bgrieger) we can assume that oil galleries are not the cause. Also, blowby has nothing to do with it. There isn't much blowby at all as there is no smoke out of the tappet cover...

Any other ideas fellas?

[bgrieger]

OK, in order to keep terminology confusion out of it, when you say oil in the extractors, you are talking about oil being inside the tubes of the exhaust manidfold correct? If it is inside the tubes, given this is not a turbo car, there are only a couple of ways to get it there, and only one is even remotely common. Your car either burned it, or leaked it. A leak into an exhaust port from a crack in the head could do it, but I've only ever seen that once on a cast iron head from a chevrolet small block. The only other way is burning. Don't rule out burning...it takes a fair amount of oil consumption before smoke is visible. At 1L per week, mine could only be seen at startup for the first 30 seconds, and in other people's headlamps at night.

Oil on the outside would come from the valve/tappet covers, and is pretty obvious.

[Robbo]

Yeah, well your conclusion is pretty much what we've had to conclude to aswell. Seeing as, like you said, there are very few possiblities as to the cause of the oil leak (yes, INSIDE the extractors) it made us really have to think as to any other possibilities that we may have been missing. We haven't fixed it yet, but it sounds like what is happening (I didn't hear everything my dad told me) is that the oil must be leaking from pressumeably the valve stem seals or the like and IS getting into the chambers, but is mixing with the fuel at such a small amount as to not cause visible smoke. I'm quite surprised (not that Im a mechanic or anything) that you can burn that much oil without visible smoke... My mate is going to take it somewhere else that might be more used to playing with these motors.

Thanks heaps for your advice guys, especially bgrieger. Hopefully I'll remember to post the results when we find out.