Thread: oil leak manifold to block?

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Guys,

Leaking oil on the back of the engine from the intake manifold.
I put a new manifold on my sbc 350. It's a 1964 block (going by the casting #'s). Right from the start I did not like the black rubber gasket that just laid on the block. I siliconed it in place but when I tightened the manifold it "squeezed" out. I lifted the manifold, cleaned all silicone and made sure all was dry and grease free, reapplied some more silicone and put the black rubber on the block and let it set for an our and this time it stayed when i tightened the manifold. But now it blew out again. The gasket set came with another gasket with two little nipples that I assume are for a block that has holes in it?
1. Is this a high pressure area?
2. How much oil should come out the distributor hole if the dist. bolt is only snug? (I think I have a leak there also).
3. Is this a common spot for leaks? Any tips on getting a good seal? I'm thinking of drilling a couple of holes and using the other gasket with the nipples?
Thanks in advance,
-Brad

Are you using a PCV and breather system? this serves to relieve the pressure building up under the manifold. If so, check that your pcv valve is functioning properly.

I had the same problem, even with the breather/pcv. The rubber gaskets that seal the front and back of the manifold are junky and leak-prone. Best solution is to pull the manifold again, make sure the block and manifold are clean as can be, and instead of using the rubber gasket, just lay down a 1/4" bead of copper rtv sealant along the block, and a bit up the sides of the heads (right up to the manifold-to-head gasket). Drop the manifold back into place, and tighten to torque spec. This should give you a good seal. It worked for me.
Good luck...

Thanks 63boxnova,
I have a pvc valve in the valve cover but it's not hooked up to anything. Does this defeat the purpose.
The front is dry as a bone, just the back leaks with RPM (at idle-no leak)
Yeah I'll have to pull the manifold tomorrow. Do I need to replace the maind manifold gasket or can it be reused?

-Brad

take the front & rear rubber gaskets & throw them in the TRASH & do what 62boxnva said. Heck even Chevy & some gasket makers don't use them anymore in their gasket kits. they just give you a small tube of black silicone....joe

Novaman,
I had the same thing happen on my 283. I pulled the intake (reused the old gaskets, applied a 1/4 bead of RTV, let it set for two hours and torqued the intake. No more leak.
In response to your leak on the distributor. I originally forgot about the gasket and never lost oil from this area, after about two weeks of running I saw the gasket sitting on my workbench.

Good luck,
Kevin

Just did a rebuild on a '94 Suburbarn with a 350. On teardown we noticed it did not have a gasket (or O-Ring) at the Distributor. 290,000 km and it never leaked there.

Yes, a disconnected PCV defeats the purpose. Hook it up to the PCV port on your carb. This will create a vacuum that will relieve pressure and fumes under the manifold, less pressure = less leaking. Also make sure you have a breather in the other valve cover.