Liquid oil in the exhaust.... and other oddities

[thstone]

Originally Posted by maytag

And what sort of numbers are acceptable for a motor at 150k miles?

Under 5% is preferable. But I'd say that anything less than 10% is probably ok on a well worn engine. This engine had 90K street miles when I installed it in my car. Then I had added 70 track hours of racing on top of those miles! That's got to be equal to 150K or more street miles.

If you see anything like 15% or 25% leak down, its time to worry. With low compression and poor leak down numbers in cyls 4 and 5, I knew that this engine was on its way out. It finally failed 11 track hours after this test.

The fact that your compression numbers are good brings hope that the leak down numbers will also be good. Best of luck.

[maytag]

Originally Posted by thstone

The fact that your compression numbers are good brings hope that the leak down numbers will also be good. Best of luck.

That's what I'm hoping, too.
Thanks for the response. Any thoughts on cold vs hot test?


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[Misfire]

I am new to the site and new to Porsche.

If I understand this event, the vehicle spun and the engine may have turned backwards.

Image one of the cylinders just fired the plug and all the valves are closed while combustion is taking place. There is pressure on the piston to push it down, however the weight of the vehicle (going backwards) does not allow the piston to go down.

The piston is forced up against combustion pressure and as the crankshaft begins to rotate a few degrees backwards, the intake valve opens,(motor is turning the wrong way). The cylinder is above max combustion pressure and this pressure is released into the intake manifold. The throttle valve is shut. The pressure takes the path of least resistance, travels past the AOS into the crankcase. The pressure expands, inside the crankcase, just enough to blow out one cam plug and unseat the others.

Any takers on this "small bang" theory?

[maytag]

Originally Posted by Misfire

Any takers on this "small bang" theory?

Plausible.
Either way, it seems that combustion gases pressurized the crankcase.

I'ma do the Leakdown. I think I'll find that things are fine (I probably just jinxed it). Then I'll feel confident buying new parts to reassemble (I'm going to do fresh coils, plugs, probably a baffle in the sump, etc etc).

Thanks again for everyone's help.