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Old 06-30-2004, 09:30 PM
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Whats the best way to seal an intake manifold

I've not had good luck lately in getting the end rails on my manifold to get a good seal. Im just wondering in your opinions what the best way to get a good seal is on the manifold. By the way I've been using oil resistant RTV instead of the cork end rail gaskets. Any ideas are welcome Thanks.

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Old 06-30-2004, 09:38 PM
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Get a hemi. They have a valley cover and don't depend on those weenie manifold gaskets.
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Old 06-30-2004, 09:47 PM
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gaskets

I usually use the manifold to head gasket and throw the rubber away and use blue rtv on small blocks chevs. what kinda problems are you having???
Jesse
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Old 06-30-2004, 10:16 PM
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Quote:
Originally posted by willys36@aol.com
Get a hemi. They have a valley cover and don't depend on those weenie manifold gaskets.
LOL@Willys


I"ve started using a product called "Right Stuff" and its great! Did both my sons 406 and my 355 and they are leak free!
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Old 07-01-2004, 03:58 AM
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Re: Whats the best way to seal an intake manifold

Quote:
Originally posted by NovaSS350
I've not had good luck lately in getting the end rails on my manifold to get a good seal. Im just wondering in your opinions what the best way to get a good seal is on the manifold. By the way I've been using oil resistant RTV instead of the cork end rail gaskets. Any ideas are welcome Thanks.
I don't use the gaskets on the end rails.

Clean the block end rails and the intake manifold. Put a 1/8th pipe plug in the oil pressure sending unit hole so that no RTV gets in there. This will be replaced with the sending unit later. Put RTV silicone sealant (I use the clear) across the end rails liberally. About 3/8-1/2 inch high. Using too little RTV will not yield a good seal. Run it up onto the intake to head gaskets some to seal the corners. It is also a good idea to put a small amount of RTV on the intake to head gaskets around the water passages only. Let it set for about ten minutes to 'skin' over. Carefully lower the intake manifold in place. Do not wiggle it around. Install the intake bolts and tighten them down to specs. Some of the RTV will squeeze out (and in, but not to worry it will not run down into the lifter valley). After the RTV has fully dried (72 hours) you can trim the excess RTV off with a razor blade.

NOTE: On some intake/head combos (RPM Air Gap to AFR heads) there will be a large gap at the end rails. AFR sells end rail spacers to take up some of this gap.
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Old 07-01-2004, 05:38 AM
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Re: Re: Whats the best way to seal an intake manifold

Quote:
Originally posted by Frisco
I don't use the gaskets on the end rails.

Clean the block end rails and the intake manifold. Put a 1/8th pipe plug in the oil pressure sending unit hole so that no RTV gets in there. This will be replaced with the sending unit later. Put RTV silicone sealant (I use the clear) across the end rails liberally. About 3/8-1/2 inch high. Using too little RTV will not yield a good seal. Run it up onto the intake to head gaskets some to seal the corners. It is also a good idea to put a small amount of RTV on the intake to head gaskets around the water passages only. Let it set for about ten minutes to 'skin' over. Carefully lower the intake manifold in place. Do not wiggle it around. Install the intake bolts and tighten them down to specs. Some of the RTV will squeeze out (and in, but not to worry it will not run down into the lifter valley). After the RTV has fully dried (72 hours) you can trim the excess RTV off with a razor blade.

NOTE: On some intake/head combos (RPM Air Gap to AFR heads) there will be a large gap at the end rails. AFR sells end rail spacers to take up some of this gap.

Does this mean to wait 72 hrs b4 you start and test the motor. After two failures I did wait 24 hrs and this was my first leak free success, but what has been your experience. Ed ke6bnl
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Old 07-01-2004, 06:36 AM
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You shouldn't need to wait at all. I've done several, including my LT1 (which are infamous for leaking at the rear). I don't wait for the silicone to 'set up' or 'skin over' either. Just use a good quality silicone (I've found that the GM stuff is the best, by far. I good bit more expensive than the local parts store/permatex stuff, but worth it). Also, using a sharp drift, or small philips head screwdriver, dimple the mating surfaces. It gives the sealant a bit more bite area. Also, clean all the surfaces well with acetone or laquer thinner, or rubbing alcohol, or whatever good solvent you have. Drop the manifold on carefully and straight so as not to smear the sealant around. By the time you have everything bolted up, fire up the engine and drive it. It WON'T leak unless you messed up the installation.

Tim
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Old 07-01-2004, 07:04 AM
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Re: Re: Re: Whats the best way to seal an intake manifold

Quote:
Originally posted by Ed ke6bnl
Does this mean to wait 72 hrs b4 you start and test the motor. After two failures I did wait 24 hrs and this was my first leak free success, but what has been your experience. Ed ke6bnl
Not at all. Just continue to mount everything and by the time you have it ready to run everything should be fine.

The 72 hour curing time is only for the removal of the excess. You don't want to use a dull blade and end up pulling the RTV out of the gap creating a leak.
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Old 07-01-2004, 07:37 AM
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i always seem to have problems if I don't use the end gaskets. So I use both every time-

K
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Old 07-01-2004, 09:07 AM
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Killer, you must be a one in a million. Your saying you have had repeated success with the end gaskets? IMO, those are the buggest pieces of junk, why they still include them in the kits I don't know. I changed the intake gaskets on a '94 Chevy truck the other day, 5.7, (coolant leak). From the factory, they were not installed, but they came in the gasket kit?????
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Old 07-01-2004, 09:34 AM
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yeah I dunno guy, I just always seem to have a leak no matter how much goop I use! Maybe I'll try again, I'm putting my intake on this weekend...

K
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Old 07-01-2004, 09:48 AM
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Just be sure to lay a good thick bead, and put extra where the heads meet the block and around the coolant passages. Just as Frisco said It sucks really bad to get the motor together and running just to have to pull the intake again for a leak. Also a good idea to apply a sealer to the threads of your intake bolts, just as you would the head and waterpump bolts. I use weather stripping sealer in these applications. Never had a problem. Congrats on your heart transplant.
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Old 07-01-2004, 10:11 AM
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I'll give it a shot bill, and thanks, it was a hell of a job.

One justification i can see for the gaskets is that the gaskets keep the intake the proper distance from the block, whereas the intake just sinks right into the black stuff, and consequently things might not match up...

k
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Old 07-01-2004, 10:19 AM
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I have always used the rubber end gaskets. Some came with cork end seals, don't use those. A dab of silicone in the corners. Have never had one leak in 35 years............just be careful when dropping the intake on.
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Old 07-01-2004, 12:31 PM
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Always use the rubber end gaskets. The best adhesive to use here isn't RTV though. It's weatherstrip adhesive.

3M makes it. use the yellow stuff, apply it adequately but not liberally to the CLEANED engine block mating surface, then apply the gasket. Now lift the gasket off, replace it, lift it off again, and you should notice the adhesive "stringing" it's a really weird process, something to practice on elsewhere to get the hang of how this adhesive works. But once you've "tacked" the gasket until those strings start forming, blow on the adhesive a little and set the thing in place, and it will be SOLIDLY adhered to the surface. The glue sets in about a minute.

Next, put dabs of it at the ends of the gaskets, and apply another bead to the top of the gasket, and do the same "tacking" process, placing the CLEANED manifold in place, then lifting it up until "stringing" starts to occur. Give it a little gentle blow of air, set the manifold in place CAREFULLY, and you'll notice the adhesive has already set.

NEVER had a leak using this method. The stuff is SUPER tacky. Try to not get it on anything else. If you do, use weatherstrip adhesive remover, also by 3M.

tbw
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