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1978 Cadillac SDV (Commodore Blue Met.)
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65 Posts
Discussion Starter #1
Hello everyone! I finally finished up removing the center plenum area from my 472/500 intake manifold and have removed the stock single plane manifold from my 425. Im ready to make the swap now but first wanted to get some advice from anyone on here that has any experience with this. I have the felpro intake valley pan gasket. Ive watched many videos on youtube of this job but their r none that r done on a cadillac and it seems that peoples techniques vary quite a bit. For one, most people seem to toss out the 2 rubber seals for front n back of block n just run a nice fat bead of rtv instead. But most of these gasket jobs r also not the valley pan style either so should i use them or toss em n go with just rtv? Also do i need to trace the port holes on both sides of gasket with rtv? If anyone can help me out with a lil knowledge on how to successfully complete this task itd sure give me alot of piece of mind. Please help and thanks in advance!
 

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1980 FBC
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3,130 Posts
I've always used the rubber seals. Do not use silicone on both sides. It acts as a lubricant before it cures and the seal may walk.

The block side can be siliconed. Be sure all surfaces are completely oil free.

A little 3M weatherstrip Adhesive works on the tops of the block to valley pan seals.

Fel Pro used to include a tube of blue colored sealant to apply to the port areas of the tin on both sides. Not sure what's out there today.
 

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1978 Cadillac SDV (Commodore Blue Met.)
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65 Posts
Discussion Starter #3
Ok thx for the advice! Yeah my gasket kit didnt come with any sealant but on their lil instruction sheet they say to put a lil on both sides of tin at tops n bottoms of ports but not on sides. I prepped the mating surfaces pretty good n an gonna give it a last min wipe over with some acetone or lacquer thinner on a rag to be sure. Would the grey rtv work in place of the 3m weatherstrip adhesive between valley n gasket? It supposedly their best sealant against oil i guess. Thanks again APEMAN!
 

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1978 Cadillac SDV (Commodore Blue Met.)
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65 Posts
Discussion Starter #4
Im also installing a trans dapt 1" spacer on top of manifold, its an open plenum spacer, so now that i cut the plenum outta my intake would i wanna take my quadrajet gaskets n cut the centers out so theyll matchup? I cant see not doin that bein a good idea, i wouldnt want those gasket pieces breakin loose n fallin down into the block. Even the one between spacer n quadrajet should be cutout right? Fingers crossed! Whenever i work on my motor im always terrified of gettin done with whatever im doin n my car not runnin as good as before i touched it, probly why everything i do takes me twice as long as it should lol, but i havent failed myself yet, better safe than sorry i suppose. Here goes nothin!
 
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