[skidplate77]

Hi All - I have put in, and taken off my intake manifold three times because of my intake gasket not sealing right on my 304. This last time I thought I had it right, until a few weeks later, I was checking around the rear of the engine with a mirror, and at the rear of the intake, next to the firewall... I noticed that the rear rubber gasket had slid off the ridge of the block it was supposed to set on.

The corners of the manifold looked sealed up ok, there are no fluid leaks coming out where the rubber had slid off in the center of the engine block... I have ran the engine some, and it runs ok, but it is a bit hard starting. I have to pump the gas quite a bit to get it to fire. Plus, to run it with the choke full open, it has to be at full operating temp.

My question is that I really don't want to take this damn thing apart again. But, I was wondering if that part of the rubber gasket being "off" would it effect the way my engine is running? I mean, the void directly under the manifold, oil splashes around in there to lube the lifters and push rods. No oil is leaking out. The intake tunnels and exhaust passeges are sealed at the heads, right?

So I was thinking that I could seal it up where the rubber sets with some silicone? And everything could be ok?? Thanks for any advice...

[swatson454]

Yeah, those end seals can be a pain in the arse. They don't like machine work or aluminum intakes and seem to take great pleasure in slipping around on you.

To answer your question, yes you should be sealed up as far as the intake runners go. Leaks on the end rails do have a tendency to mist and weep on you due to crankcase pressure, though. Not to mention if oil can get out, then crap can get in.

In my opinion, a bead of black silicone instead of those rubber end seals is the way to go. A bead roughly half the width of the block, so it doesn't squish out all over the place, has always worked well for me.

Hope that helps,

Shawn

Holley Carburetors

[Fatman]

You need to pull the intake and get yourself another set of gaskets.
If not you will have a big time vacuum leak.
Clean the mating surfaces well and DON'T use the rubber front and rear gaskets.
Build up these surfaces with 1/4" of high temp RTV as well as on orbit around all of your water jacket ports.
Again, only use the paper gaskets at the head / intake mating surface.