intake manifold gasket question


Senior Member
I am using these Fel-Pro ulta-seal gaskets to put my weing action plus manifold on my chevy 350. Around the ports the gasket has raised rubber. My question is should I still use rtv sealant? I have had the worst time trying to get past intake manifold installations to not leak water. I am therefor weary of not using RTV sealant. Shoul I just goop the heck out of the thing? What do you all do?
Hey Garet:

The "raised rubber" that is around the intake and water ports on your gaskets is the only sealant that should be applied. This is a silicone-based sealer that is actually silk-screened (like t-shirt designs are) onto the gasket.

You can still use a dab or two of RTV on the head side of the gasket to help hold it in place while you position the intake on the engine, but if you apply RTV over top of the existing silicone, you run the risk of an incompatibility between the two compounds, creating a leak. This chance is small, but still exists.

If you are uncomfortable with this, return the Fel-Pro gaskets where you bought them and buy yourself some generic, run-of-the-mill gaskets and goop away.

My personal experience with Fel-Pro gaskets has been extremely good. I have never had a Fel-Pro brand gasket fail when I've properly prepared the surfaces (use mineral spirits, alcohol, brake parts cleaner or some other non-petroleum based cleaner) and torqued the part to specifications.

If you read Weiand's installation instructions, they probably specify in the neighbourhood of 25 to 30 ft-lbs of torque. This may seem like not very much, but it is very common when using an aluminum intake matched to cast iron heads.

And be sure to follow GM's sequence for torquing the intake manifold bolts. It usually starts with the centre bolts and spirals outward, and torque them in 3 seperate steps - 10 ft-lbs, 20 ft-lbs, and then final torque.

I have found it helpful to use washers underneath the bolt heads. This prevents the bolts from digging into the soft aluminum and also evens the pull on the bolts, ensuring a smooth rise to the specified torque value.

You should have no problems if you follow these tips.

Just a question: in the past installations you've done, where has the water leaked to? Outside of the intake and then onto the ground, or does it leak into the engine? What sealants were you using? What brand of gaskets seemed to give you problems?

What else does Weiand recommend in their installation instructions re: types of gaskets to use?

Good luck.



Senior Member
past problems

I have always had water leaking out into the engine oil. I know this could be a head but when I last installed an intake manifold there was water directly underneath it in puddles and obvious places where the gasket failed and coolant tracks were visible on the gasket. I did put rtv on the manifold side which is probably the exact opposite of what I should have done. I don't think there should be an incompatibility issues between the rtv and the stuff on the gasket but if there is I guess off it comes again. I also put it on the head underneath the gasket. Anyway, I just bought a vacuum guage which should tell me if the manifold seal is holding true. Course it does;t tell me much about a water leak...
Another test you can perform would be to rent/borrow a cooling system pressure checker.

This hand held pump has an adapter that screws on in place of the radiator cap. You pump up the cooling system until the gauge on the tester shows about 15 pounds per square inch (normal operating pressure). Leave the tester attached and watch the gauge to see if the pressure remains at that level or if it drops.

If it drops, you have a leak in the cooling system. Check the easiest things first, which will be external leaks.

If none are found, you *may* get lucky and be able to see evidence of the leak into the engine by removing the valve covers, shine a strong light through the oil drainback holes in the cylinder head and around the pushrods.

If this doesn't seem to tell you where the leak is, the next step is to use a flourescent dye in the cooling system and a black light will expose any leaks you will have.

You should also be able to rent the black light/dye kit from a better tool and parts supplier.

Another check that I always perform when bolting on an intake manifold is to set the intake onto the engine without any gaskets in place. The mating surfaces between the intake and the heads should be parallel and flat -- in fact, the intake should rest on the heads and there should be a gap on the front and rear edges of the intake where it mates to the block. If not, that 1/16" to 1/8" that the gaskets will add will probably no compensate, and not matter how hard you torque down on the bolts, the manifold will bottom out on the block before it can properly compress the gaskets.

Just a few more of my thoughts -- take them for what you will.