Greg Fiorentino wrote:
The
route from the cylinders to the inside of the valve cover could only be the
valve guide seals.
I don't see how this is true. Can't gasses freely flow between the
crankcase and the head through
the oil drain passages? In that case, the most likely route for
combustion gasses to pressurize the inside of the valve cover would be
blowby past the piston rings, not the valve guide seals. Many engines
mount the only crankcase breather onto the valve cover for this reason.
The valve guide seals don't experience much pressure at all, since
they're outside the valve. At most (with a turbo) they experience the
head pressure driving the turbo, and the output boost from the turbo,
but on an NA engine they experience slight vacuum on the intake side,
and very low pressure on the exhaust side.
I would suspect a clogged crankcase breather, or excessively worn piston
rings before I'd suspect the valve seals.
Tyler
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