valve covers wont stay tight

Ive done changed my valve covers twice now, replaced gaskets, used just about every kind of sealant there is and they leak oil constantly. I have a 1970 GMC truck, 350 , 286 comp. cam .

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Most modern valve cover gaskets do not use any sealant, check the covers for being warped or dimpled at the bolt holes from being over tightened. Make sure the cyl head drain back areas are not clogged, also.

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Do you have spreader bars under the bolt? Are you tightening the bolts to the recommended spec? Make sure that the bolts do not bottom out or have bad threads. Make sure that the gasket edge of the cover is flat and that there is no damage to the head. If all is good and it starts to leak try to re-torque to spec.

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gmc70 wrote:

In those years, GM had a pretty sad valve cover gasket setup. The covers are tin, and if they aren't straight you can have problems, if someone has overtightened the bolts and deformed the holes in the valve cover you can have problems. There was a "spreader" kit that GM had for those older valve covers. You would get studs that screwed into the cyl heads, and large spreader bars that went on top of the valve cover at each hole. They also had a special set of valve cover gaskets that you used with the kit. The spreader bars helped to spread the clamping load over more of the valve cover area.
You could also use RTV, but you have to make sure the mating surfaces are perfectly clean and dry (no oil).
Ian
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What Ian says in his post about the early small block valve covers is right on, I've always opted for an aluminum set. They are much less prone to leaking.
Brian
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I was fooled by leaky valve covers on a small block once. Turns out all along it was the oil presure sensor at the rear of the block. Its really hard to see it and it looks for sure like it the rear of your rocker covers leaking.
gmc70 wrote:

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That's a good point, the rear of the intake gasket can also fool you if you don't look close enough.
Brian
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If it has a PVC system are you sure it's working and not pressurizing the crankcase? If so the oil gets pushed out through the weakest gaskets.
Ted
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