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I have a 1977 f250 with a 400m. i keep having issues with blowing out my valve cover gaskets every couple hundred miles, ive tried cork, and rubber gaskets, ive been able have the cork last a little longer than the rubber gaskets though
First, and no offence, it's a 400, plain Jane 400... not 400m....you have a 351M, 351C and the 400.
Onto the issue at hand: Do you have a clean PVC unit hooked up, and a clean valve cover breather?
Are your valve cover bolts just a little tighter than finger tight? I think 5 -7 inch lbs.
If they're too tight, they'll disform the valve cover and crush the gasket too much, allowing leakage.
Do you have any kind of oil spew from the dipstick?
Brand new pcv and breather, i do not have cast valve covers, valve covers are straight and the bolts are all hand tight then tinghtened 1 quarter turn with. 1/4 drive ratchet
First, and no offence, it's a 400, plain Jane 400... not 400m....you have a 351M, 351C and the 400.
Onto the issue at hand: Do you have a clean PVC unit hooked up, and a clean valve cover breather?
Are your valve cover bolts just a little tighter than finger tight? I think 5 -7 inch lbs.
If they're too tight, they'll disform the valve cover and crush the gasket too much, allowing leakage.
Do you have any kind of oil spew from the dipstick?
Excess crankcase pressure is usually caused by poor ring seal. In my experience, it is much more likely to show up at the dipstick vs blowing out VC gaskets. At idle, if you pull the dipstick is there a lot of gas flow and maybe oil coming out?
The VC is tricky to seal... best case you just have an issue with fit or flatness of the valvecovers or gasket.
If there is a ring seal problem, it would usually also show up as excess oil consumption and maybe fast "blackening" of the oil. Is there any of that going on? Also low or uneven results on compression test.