Im changing my intake manifold. Do I need to have a seal around it? I ask because I was taking apart a different 350 and it had a seal on the intake manifold (an apoxy rubbery type material)

 

What part are you talking about? There are typically four parts that come with an intake gasket kit for a SBC: Two intake manifold gaskets - these go between the intake manifold and cylinder head and are required for proper sealing of the intake system and cooling system.

There are also two rubber end-gaskets, and these are supposed to go between the bottom of the intake manfold and the front/rear of the engine block. They look like flat noodles made of black rubber. Those are not used by 99% of people, because they always leak. Most people toss those in the 'circular file' and instead build up a bead of gasket silicone on the front/rear of the block, between the heads, about 1/4" high and set the intake manifold down on top of it (after the intake/head gaskets are put on the head of course) and let it cure.

This makes a much better seal than the rubber end-gaskets, also called the 'China Wall gaskets'.

 

So what your saying is go down to a part store and pick up a intake gasket kit and some silicone? Why would I replace some gaskets/seals in the front and end of the engine block if all i was changing was the intake manifold?

 

Ok now I'm confused as to what exactly you are asking about....?

 

If I understand you correctly, you are just changing the intake correct? No water pump, no timing cover, etc. Right?

If so, to elaborate alittle more, picture the intake as being a rectangle. 2 of the sides are sealed by intake to head gaskets. These gaskets seal the intake charge (air and fuel mixture entering the cylinder head) and they also seal the coolant passages between the cylinder head and the intake.

The other two sides, at the front and rear of the engine, needs to be sealed to prevent dirt and grim from entering the engine and to prevent oil from coming out. On the front and back of the engine block is a ridge between the two heads above the lifter valley. Take some Black RTV and apply a 1/4" bead across this ridge. Put the intake gaskets on the heads, and then sit the intake on. Install your bolts finger tight. Now starting at the center of the intake, slowly start tightening the bolts working from the center most bolts out. Gradually increase the tightening force until it is completely tight.

 

Ok I understand a little more now. Thanks for the help guys. The intake is actually for a different car, a 75 chevelle. But I thought I'd ask you guys because you all seem to know pretty much everything