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patkeefe patkeefe is offline
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Join Date: Apr 2004
Location: Ringwood, NJ
Posts: 2,794
Oil Ring in the Sump

Three weeks ago, I had the SC at Watkins Glen. First run group, it was a bit lean, so I came in and adjusted the WUR, which got it acceptably rich according to my AFR gauge. It warmed up some more a bit later, so I had to repeat the process, this time I had to lean it a bit. I did also notice I was getting what seemed to be a bit more crankcase pressure at the oil tank. I thought about it, and figured maybe I had it so rich that I may have washed some oil off the cylinder walls or something stupid like that. Anyway, I felt no cause for alarm at this point, figuring one more run and see what's up after that.

Just before lunch, the car was making as much power as I have ever felt in it. I was screaming up the esses on top of 4th gear when the car filled up with oil smoke. I shut it off and blindly coasted to a stop, and of course, put the fire out on the heat exchangers, as I had dumped a bunch of oil. Made a mental note regarding new Nomex suit. They towed it in, and I put it in the trailer, and ignored it for 10 days. I have not run it since, although I did turn the engine over via the starter.

I thought maybe I had a leak in the turbo feed line, but couldn't find evidence of it. So, this week I drained the tank...a half inch bit of oil ring came out. Real good for the oil pump, I thought, as I started doing damage assessment in my head. Another 3/4" bit came out of the sump. Crap!

I'll get the engine out this weekend, and see what's left of any use.

I have some speculative ideas as to what broke, just don't know why at this point. I didn't see any compression rings, or piston bits, just oil ring. I was only running 7 PSI boost at the time. Documented failure analysis to follow, for posterity. I am having trouble correlating broken oil ring with massive loss of oil, however, unless the crankcase pressure blew out the oil seal at the crank (doubtful).

It may be time to just get a real 930 engine for the car, or put cams, pistons and carbs on the 3.0, if there is anything left worth a crap in there. I have grown acustomed to the boost, so I don't think I want to revert back to n/a. We shall see.
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Patrick E. Keefe
78 SC
92 968 Cab
01 Boxster
RIP, Early_S_Man & RoninLB
Old 10-11-2008, 05:34 AM
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