Oil Leak

[frankfast]

I can't find the source of an oil leak at the head of my 350. I thought it was from the exhaust side valve cover but after smearing silicone gasket seal it doesn't look like that's the source. Oil is seen just below the valve cover on the left side where the valve cover transitions to the finned part of the head. I'm beginning to think that there is a crack or a very porous part of the casting at that point. Has anyone had any trouble leaking oil in this area?

[graeme]

Hello Frank

Best way to locate a leak is clean the area with fuel so there is no oil residue then cover the area in talcum powder.
You'll see the leak easily by the wet talcum powder.

Graeme

[jbcollier]

Is it a Desmo? Demo closing rocker pins can leak oil into the head stud holes which then migrates out just below the rocker covers. New closing rocker spindle o-rings should solve the problem but you need to fit them with care.

[Rocla]

Hello Franck,
I've had a leak on my 350 Scrambler and one day, i've discovered the cause: the seal on the top of the bevel gear axle housing. I was forced to add a second seal to stop the leak, simply because there is probably an error of dimensionning this housing versus the cumulated lengh of cylinder + head (both have to match). Almost half a milimeter was missing. With brand new seals (1 on the top and 1 on the bottom), it was still leaking. The leak was only stopped thanks to 2 seals on the top...