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Sealing intake mainfolds: RVT,cork gasket or rubber gaskets?


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Guest Want aZ

Ive always used the neoprene gaskets on the ends of the block and used RTV Sealant in the corners to insure that I got no leaks, although I did use small bits of RTV to ensure that the gasket didnt move when dropping the intake in place... never have had a leak at either the front or the rear of the intake/block junction....

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I've never used a gasket on the ends of the intake (front or back), and have never had a leak. Put the intake on, and measure the gap. Then squeeze out some silicon bead a little fatter than the measured gap. Let it set up for a few minute and then bolt everything up. Leave it overnight before heat cycling it.

Tim

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Guest the_dj

I use gaskets with RTV on both sides. To clean the surfaces, there is nothing more wonderful than the 3M gasket remover pads for the drill. I was in heaven using those things. 5 minutes of easy work and EVERYTHING was polished to a shine w/o any material left over!!!

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clean BOTH the lower intake pads and the block rails then degrease with a rag damped with acetone,dimple both the block rails and lower manifold matching pads with a center punch several dozen times on each end and each surface, then degrease with the damp rag again , place a 1/4" thick bead on the lower intake surfaces (black RTV) then a 1/4" wide bead on the block rails , then carefully install the intake, the two beads will blend, let them dry inplace for at least 8hrs the little dimples add greatly to the holding ability of the RTV

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Grumpy's advice is spot on. I have had BAD luck with the blue, orange, and red sealers. Permatex Black is the only one I use anymore. For the gaskets themselves, I brush both sides of each with GM gasket sealing compound. Comes in a can with a brush from your friendly dealer. Makes good head bolt sealant as well.

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Is the factory sealant more difficult to clean off than the Black RTV?

If it is and the regular Black RTV is good enough, I'd stick with it.

 

Grumpy, thanks for that tip on the dimpling and a bead on both the manifold and block rails.

 

Also, I put non-hardening permatex sealer only around the water passages on the side gaskets. I use a bit of grease elsewhere to keep

them from sticking. I hate messy cleanups, especially in this area where you need to keep trash out of the valley. I mask all that off, but less trash is still better.

 

Don't forget sealant of some kind on the intake manifold bolts. the center 2 on each side go into the crankcase area and can weep oil up the threads. The ones just adjacent to those near the center around the water passages go into the water jackets and can weep water/coolant. The most forward 2 and most rearward 2 are blind, no sealant needed, but doesn't hurt.

 

Comments on what I might be doing wrong always appreciated!

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good info here. i use ultra blue in the same manner as Tim240Z described, using carb cleaner like pete p described and no gaskets on the front or back of the intake. i've never had leaks from rtv on the front or rear of the intake. front timing cover seals are another story... other than that, if you are using aluminum heads, be sure to retorque your intake bolts periodically.

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