1964 390 valve cover leak

iwinyouwin

Active Member
I have replaced my 64 valve cover gaskets twice on my 390. Once with cork and once with rubber. My valve covers are chrome and say THUNDERBIRD on them so I hate to replace them. I have had to try and straighten them, probably from a previous over-tightening, since it leaked when I bought it. I am getting some oil leaking out both the top and bottom of the cover and I replaced the breather oil cap and it did not help - the covers themselves do not have a breather cap just the oil fill tube. At times I have wondered if there is any back pressure on the valve covers causing the leaks.
Any thoughts or suggestions where I do not have to replace the existing valve covers?
Any suggestion on valve cover replacements if that is my only alternative. New repo or OEM vs Cast Aluminum
 
turn the covers over and on a straight edge make sure there are no gaps. if have gaps, straighten with a narrow piece of wood and a small upholstery hammer. make sure all mating surfaces are clean and dry. do not use rubber, use cork. use either weather-strip adhesive or 3M 777 spray adhesive. DO NOT use silicone! spray the valve cover and one side of the cork gasket. do not spray or glue the side that sits on the head. let the adhesive tack up before joining the gasket to the valve over. let it dry. then install the cover as usual. tighten with your non-dominant hand moderately. that should do it. don't need to replace valve covers. material coming from the oil fill cap might just be blow-by. can also use Permatex high tack spray-a gasket sealant. good luck
 

Dale Leonard

Blown Valkyrie Rider
turn the covers over and on a straight edge make sure there are no gaps. if have gaps, straighten with a narrow piece of wood and a small upholstery hammer. make sure all mating surfaces are clean and dry. do not use rubber, use cork. use either weather-strip adhesive or 3M 777 spray adhesive. DO NOT use silicone! spray the valve cover and one side of the cork gasket. do not spray or glue the side that sits on the head. let the adhesive tack up before joining the gasket to the valve over. let it dry. then install the cover as usual. tighten with your non-dominant hand moderately. that should do it. don't need to replace valve covers. material coming from the oil fill cap might just be blow-by. can also use Permatex high tack spray-a gasket sealant. good luck
Also make sure you clean the mating surface on the head with a good solvent and a rag to remove any oil that is on the surface
I have replaced my 64 valve cover gaskets twice on my 390. Once with cork and once with rubber. My valve covers are chrome and say THUNDERBIRD on them so I hate to replace them. I have had to try and straighten them, probably from a previous over-tightening, since it leaked when I bought it. I am getting some oil leaking out both the top and bottom of the cover and I replaced the breather oil cap and it did not help - the covers themselves do not have a breather cap just the oil fill tube. At times I have wondered if there is any back pressure on the valve covers causing the leaks.
Any thoughts or suggestions where I do not have to replace the existing valve covers?
Any suggestion on valve cover replacements if that is my only alternative. New repo or OEM vs Cast Aluminum
I agree 100% with vim berg. But also do this. Also make sure you clean the mating surface on the head with a good solvent and a rag to remove any oil that is on the surface before putting the valve cover in place. Any oil on this surface will cause the gasket to squeeze out and cause a leak. The dryer and cleaner the better.
 
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