I am looking for the best way to seal the intake manifold on my 352, I am using the stock cast iron intake and the stock cast iron heads, I have tried using the gaskets from the rebuild kit and sealing them with gasket sealer, and it still poured oil out, so then I tried just using silicone, and it leaked even worse, what have you used in the past that has worked, I want it to be completely leak free.

 

I have had the best luck with Blue RTV. You need to make sure that you get it good in the corners but don't block the oil drainback with it. With my stock cast iron I did have real good luck with the cork end seals though. You still have to put silicon in the corners.

 

I always try to dry fit the intake before installing the cork end seals. That way you know how much clearance you have and know that they won't slip/push out. I know that's alot to ask for a cast intake, but it makes a better fit.

Like Ratsmoker mentioned, make sure you get some silicone at the corners to seal where the drain holes are in the corners of the heads.

If using the cork ends, put a small amount of silicone down to help hold them in place, but not so much that it tries to push them out when you put intake on. Let it set up a bit(so they don't move easily). Put nice dab on each corner before installing intake.

Glad to say that's the ONLY place my FE's dont seem to leak

 

And make sure the mating surfaces are clean of any traces of oil, as it will interfere with proper bonding. Carburetor cleaning spray (Gumout?) works pretty well for cleaning those surfaces.