Are 4.0 valve covers head specific ??????? -
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Unread 07-20-2009, 03:03 PM   #1
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Are 4.0 valve covers head specific ???????

I just completed a 4.0 head swap on my 258, I got a valve cover off a buddy since my new head did not come with one. This valve cover does not seal to the head. Bought the $36 fel-pro perma dry gasket and leaks like a cive.... I was told that the valve covers are head specific such as to each casting #. Any help would be great my casting # is 0630 and the valve cover im using has a lip around the bottom which is not letting it seal to the gasket.

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Unread 07-21-2009, 09:14 AM   #2
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the answer is ... sort of... the early 4.0's will interchange with a 4.2, I believe the 91 to 95 might as well though Ive never tried to interchange between a renix (86-90) or 91-95 with a 4.2 valve cover or vice versa.

The 96 and up is a stamped steel valve cover, as you've found the head is slightly altered so older covers don't fit without grinding that lip off. So that's why it's "sort of" you can easilly grind that lip off and achieve a decent seal using the 96 and later rubber pre-formed gasket. It uses rubber o-ring style reuseable gasket And it's the best valve cover/gasket combo ever made for a AMC straight six IMHO anyway...

The steel helps, but the thick rubber gasket with crush spacers in the cover to keep one from torquing the cover down way too much and distorting the cover is the least leaky of them all (by far) in my experience.
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