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Originally Posted by dookeye
yeah, it didn't seem likely that that much oil could be running all the way back through the throttle body.
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On the contrary, that is exactly what was happening in my case. Because I left out the check valve, and hadn't yet figured to motify the head gasket, oil was backing up in the head and flooding through the PCV system and into the thottle body where it then became part of the combustion process, and blew huge plumes of smoke out the tail pipe.
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Originally Posted by dookeye
I'm guessing that if this valve fails, it will fail open?
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The only way for this valve to fail is if it clogs or if its not there at all. If it clogs, the head looses lubrication. If its not there, too much oil will shoot into the head.
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Originally Posted by dookeye
How often have you encountered head gaskets that have gone bad with Metros? I have not seen much anecdotal evidence of this which again steers me towards suspecting valve seals on my car.
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The only times I have seen head gaskets go bad on metros is with either old age, or overheating - the general causes of head gasket failure (in non-high performance vehicles at least). Aluminum is much more prone to failure through excessive heat cycling (than cast iron). An aluminum head, or an aluminum block for that matter has a given number of heat cycles it can endure throughout it's service life, until it becomes too soft to maintain a flat surface with the head gasket. At this point in it's life, the head and block become insalvageable, even machine work will only temporarily restore it's use. I could go on, but the point is, a head gasket does not just fail, and if it does, it usually will not cause oil consumption into the combustion chamber, at least not until long after it starts to manifest in other disturbing symptoms; such as coolant in the oil, oil in the coolant, water consumption into the cylinder, and compression loss across adjacent cylinders.
What I meant to suggest earlier, is that perhaps someone had assembled your engine incorrectly, as I had, by not installing the check valve into the block before installing the head. And seeings how your compression is strong, and a blown head gasket will not cause oil consumption as a solitary symptom, you are left with either A) the engine is assembled improperly B) you have bad valve seals C) your oil pump is over pressurizing the system (stuck pressure relief valve you mentioned earlier) and not dumping off excess oil back into the pan, or D) the oil drainback holes in the head gasket have become clogged with oil sludge from old age.
Also note, that when i said that none of the engines drink oil to date, i was refering to the engines after I had figure out the relationship between the check valve and the drainback holes. No checkvalve means you must enlarge the drainback holes. If you do not enlarge the drainback holes, you must install the chekcvalve. If you have no checkvalve, and un-modified drainback holes in the head gasket, you will get oil through the throttle body via the PCV system. I apologise if I'm a bit scattered, i really am trying to clarify lol its a bit late.
MechanicMatt