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putting new intake manifold gaskets on(edelbrock manifold 390) I have it about ready to bolt on, but Ive been reading that people have said not to use the cork end gaskets???? I have them siliconed in place. should I pull them off and just use the silicone??? Why are the gaskets not good to run?
I use them, but I like to seal the bottom side of all the intake gaskets and just sit the manifold down on them and let dry over night. The seal the top and bolt into place. Most people do not like the cork because they slip out of place when bolted down, that's why I do it the way I do. FE engines are bad about leaking at the front and rear intakes.
Yes the FE's intakes are bad at leaking at the front, back and corners. I've had good luck using Right Stuff gasket maker on 3 FE's now. It comes in an aresol can like cheese whiz. I just lay down a nice thick bead, front and back and be sure to get the corners good too. Make sure you get enough squeeze-out when the intake is set in place. Never had a leak using this stuff. It remains flexable and won't dry out. The cork gaskets can dry out and crack, slit and leak like crazy. Good luck.
I've used the cork gaskets without problems. Trick is to silicone them down and leave them alone until the silicone sets up.
I don't find the cork too thick unless things are done like decking the block, planing the heads and intake...things that lower the intake manifold from stock.
All that aside, I now do what others do and just use a good bead of silicone and save the cork for the woodstove.
I just went with the cork, I already had it mostly back together, and wasn't about to tear it apart again. It had the cork gaskets in it before. I also did the silicone them in place and let them sit awhile. So far everything is just fine.
When I used the cork end seals and I RTV'd them they kept the intake raised up to much off the heads to where they didn't seal at all, I removed the end seals and just used a thick bead of RTV on the ends and corners and no problems, I have the edelbrock Performer 390 intake.