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

[911monty]

Originally Posted by maytag

Okay, I like this working theory (thanks, by the way). The only question it leaves unanswered for me immediately, is probably born from not having a full-scope view of the AOS system in it's entirety: if it's wide-open, as you've postulated, why is it ingesting oil and not air? Do I have a drain-back that's blocked somewhere, keeping the "intake" of the AOS fed with oil?

Short answer is the AOS is ingesting both. If you look closely at the AOS the bellows at the bottom of the de-mister section is directly attached to bank 1 right over the camshaft drive chain. It is attached to bank 2 through the long convoluted tube that crosses over the engine. Due to pressure drop across that tube the AOS will preferentially draw from bank 1. The million dollar question is why did the plugs blow out of bank 2? Still no answer to did the engine spin backwards, but I'm going to say probably. My theory basically is that one cylinder had recently fired but did not get to exhaust valve open. When the piston reversed, the compression ring lost seal on the piston ring-land and dumped as blowby into the crank case. Excess pressure in the crankcase popped the plugs before it could bleed through that long tube to the AOS which had no where to dump due to loss of vacuum in the intake tract when engine quit running. Pressure then relieved through the first weak point. I don't have the dimensions of the plug that popped out but I'd estimate about 3" diameter? Doing the math that puts it ~7 square inches. A cylinder head pressure of only 2 psi would exert 14 lbs of force against that plug.