Intake Manifold Gasket 67/327/300

[Gerard F.]

Thinking about taking the intake manifold off my 67/327/300 for the first time (75,000 miles), and replacing it with a very nice correct intake manifold I acquired. What is the best gasket for this application and do I use any gasket sealant.

Should I also use new bolts. Any other things I should be looking at while it is off. Are there any step by step instructions available on this project.

[Frank D.]

Re: Intake Manifold Gasket 67/327/300

This is what I used.....article by John Hinckley...... Great tips including products to use and the neat employment of a dowel through the intake distributor hole to get the alignment right the FIRST time! One update to John's article is that many swear by Permatex's "Right Stuff" sealant now for this job. Unless your car is judged I would avoid using the rubber end gaskets on the "Chinese walls" -- they are nearly guaranteed leaks. A bead of sealant works much better.

New bolts are a good idea and many use fuel injection gaskets to block off the heat riser ports to reduce fuel percolation....most that do this also wire open or put a spacer in the passenger side exhaust manifold heat riser.....so the exhaust gases have an exit on a cold engine!

The same result can be achieved by plugging the 'hot slot' holes under the carb... You can drill and tap those holes in the new intake while it is off the car to accept plugs; its easier and the mod is invisible. My 250hp intake had the holes (pics are before and after the plugs).

[Timothy B.]

Re: Intake Manifold Gasket 67/327/300

Jerry,

The first thing I would do is remove the oil splash pan rivets and pan and take the intake manifold to a machine shop to be shot peened. This will clean it like new, you can also have them tap and install the 1/4' plugs for the hot slot but explain to them they need to be tight so they don't tap completely through.

The rivets for the splash pan are still available or you can tap and install small screws with loctite. You may be surprised how much oil coke is burnt on the bottom. You may consider taking both manifolds to be done at the same time.

When you install the manifold to the engine get the Paragon gaskets that match the original shape and my opinion is to use the rubber seals. Your engine has never been decked so alignment should be fine. When I attach the rubber end seals I used 3m super weatherstrip adhesive and put a coat on the block and also on the bottom of the rubber then when it sets stick them on the engine.

For the side gaskets I used some permatex ultra black rtv around the front and rear water jacket openings both sides of the gasket. I also put a daub in the corners where the side gasket meets and set in the rubber gasket. I cleaned the original bolts and put some permatex #2 around the threads and installed them, run a 3/8x16 tap through the holes.

Frank's idea about the alignment dowel is good and a extra hand is good just sitting it on the block. The alignment dowel is in the shop manual I think.

For the valve covers I used ultra black and glued the gaskets to the valve cover them set them flat over night, the next day I think I installed them without any other sealer on the bottom gasket surface. PIA getting these steel valve covers to seal good.

[Jim D.]

Re: Intake Manifold Gasket 67/327/300

You will want to have the intake gasket sealing surfaces checked for straightness. High mileage cast iron intakes sometimes grow/mushroom slightly around the exhaust crossover ports. That makes it almost impossible to re-seal them without a vacuum leak at the bottoms of cyl.'s 3,4,5 & 6 and sucking in oil.

[Joe R.]

Re: Intake Manifold Gasket 67/327/300

This is what I used.....article by John Hinckley...... Great tips including products to use and the neat employment of a dowel through the intake distributor hole to get the alignment right the FIRST time! One update to John's article is that many swear by Permatex's "Right Stuff" sealant now for this job. Unless your car is judged I would avoid using the rubber end gaskets on the "Chinese walls" -- they are nearly guaranteed leaks. A bead of sealant works much better.

New bolts are a good idea and many use fuel injection gaskets to block off the heat riser ports to reduce fuel percolation....most that do this also wire open or put a spacer in the passenger side exhaust manifold heat riser.....so the exhaust gases have an exit on a cold engine!

The same result can be achieved by plugging the 'hot slot' holes under the carb... You can drill and tap those holes in the new intake while it is off the car to accept plugs; its easier and the mod is invisible. My 250hp intake had the holes (pics are before and after the plugs).

Frank,

Thanks for sharing John's article! It is very thorough! I've only done this job once and on a 283. Well, twice if I'm really honest because I didn't get the intake manifold aligned perfectly when I sat it down the first time. I wound up buying some long bolts and cutting the heads off them. I installed them in the heads at the four corners. It made alignment a snap! I don't know that it's any easier than John's way, but it did work.

Joe

[Mark P.]

Re: Intake Manifold Gasket 67/327/300

Frank - I decided to have my machine shop add the 2 plugs like you did to my 327 300HP manifold. I think I will start off blocking the drivers side and see how it runs. I can always add the passenger side plug and wire open the heat riser if I need to. What I like about your suggestion is this will be a lot easier to dial-in than to block off at the gasket. Pulling the carb is so much easier than pulling the manifold. The machine shop is charging me $20 to add the 2 plugs which is reasonable. They will do this before they clean all the passages and reinstall the heat shield. Thanks Mark

[Joe L.]

Re: Intake Manifold Gasket 67/327/300

Thinking about taking the intake manifold off my 67/327/300 for the first time (75,000 miles), and replacing it with a very nice correct intake manifold I acquired. What is the best gasket for this application and do I use any gasket sealant.

Should I also use new bolts. Any other things I should be looking at while it is off. Are there any step by step instructions available on this project.

Jerry------


A GM #3734115 would be the best but I doubt you'll find such a set. Otherwise, I think the most correct and best performing gasket set is the reproduction offered by Paragon.

I use a very thin film of RTV around the water passages and none on the rest of the gasket.

If you find any bolts with damaged or corrosion-eroded threads replace those. Otherwise you can re-use the bolts.