A few further thoughts regarding Michael's persistent valve cover leaks:
In my misspent youth I worked on a few American cars that used cork valve
cover gaskets. Someone (can't remember who) told me that if the cork
gaskets are old and hard they won't seal worth a darn unless you soak them
in warm water for a while to soften them up. Sure enough, when they are
soaked for a while they become a lot softer and are much more pliable so
that they fill in the less-than-perfect void between the valve cover and the
head. On my 69 TR6, I am running an aluminum valve cover, but I just dab a
couple of spots of gasket sealer on the cover to hold the gasket in place.
I use no other sealer, and the gasket doesn't leak. This also makes it a
lot neater and quicker when you pop off the cover to do a valve adjustment.
I think if you have a straight cover and a pliable gasket that fits the
cover-to-head interface well, it just shouldn't leak under normal
circumstances. Otherwise, leakage might be the result of excessive
crankcase pressure from either leakage past the valve guides or piston
rings, or maybe a crankcase ventilation system that isn't doing its job as
Dick Taylor suggested. I had a really high mileage Ford V8 once that leaked
like a sieve from the valve covers until I replaced the PCV valve with one
from a much larger displacement engine with a larger orifice. The oil leaks
then dried up. I realize that the TR doesn't use a traditional PCV valve,
but I would certainly make sure that the system isn't allowing pressure to
build up in the rocker chamber.
By the way, I have a neat little pamphlet from Fel-Pro called "Gasket
Installation Manual" that describes the theory behind each type of gasket
and oil seal, and how each type should be installed to prevent leaks. I
obtained mine at an auto parts store a few years ago, but maybe Fel-Pro
still prints the little book. I heartily recommend it!
Rex Townsend
1969 TR6
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