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How to make sure a sb chevy intake will seal?

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How to make sure a sb chevy intake will seal?

Postby drifter » Wed May 26, 2010 7:40 pm

What checks do you guys do before installing a intake manifold on a sb chevy to make sure it will seal? I have put on 2 now in the last year or so that came back with vacum leaks at the top of the intake ports.I normaly just put the gaskets on the heads and smear some right stuff silicon around the ports on both side of the gaskets & cooling jackets then sit the intake on install all bolts and snug the 2 center ones on the left & right first then work my way out.I dont think i can lay the intake on the heads without any gaskets to see if the fit is good because i'm sure the ends will hit the block before the sides of the intake touch the heads?
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Re: How to make sure a sb chevy intake will seal?

Postby zums » Wed May 26, 2010 7:47 pm

check your head angle,should be 10 degrees from deck to in flange- compare to intake,check port alignment, bolt up as you say, loosen all valves,attatch an aluminum plate to carb pad with a vac fitting, pump it up, a good valve seal/ intake seal should take over 9 minutes to fall from 15" to zero, pass that and sleep well
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Re: How to make sure a sb chevy intake will seal?

Postby needforspeed66gt » Wed May 26, 2010 8:45 pm

Silicone on both sides of a gasket tends to make them squeeze out.

I use 3M weatherstrip adhesive on one side of the gasket, around the water passages and ports - set the manifold in place and tighten four corners to set the gaskets. Then later take it off and wipe a very thin film of silicone around the ports and torque everything up. It will never leak this way as long as the torque is re-set after a heat cycle.
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Re: How to make sure a sb chevy intake will seal?

Postby novice<ismyname » Wed May 26, 2010 9:05 pm

I use silicone on the intake gaskets as right stuff is expensive but works too. End seals is where I use right stuff.
I used to glue them but don't like cleaning that later so I let the silicone cure some before tightening and never have pooched one out.
Before I tighten I wiggle the manifold to get the best port match I can.
Snug it and let it set awhile before tightening.
I use an engine lift plate with 2 gaskets to pressurize
I take mine to about 10#, they usually leak at the lift plate because the steel plate is too wimpy and needs more fasteners.
You know it immediately if you have an intake gasket leaking though.
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Re: How to make sure a sb chevy intake will seal?

Postby vincenelson » Thu May 27, 2010 2:40 pm

Well I like to use the softer style gaskets like Mr. Gasket, I use yellow snot gasket sealer on one side and make sure that I have it on all around the ports and water jackets, then on the top side of the gasket I use silcone grease about a 32nd of an inch thick everywere. I then install the manifold using blue silcone glue on each end with the cork or rubber gasket, again with yellow snot on the bottom of the cork gaskets. I tighten down all the bolts and let it set until the blue silcone sits up. I have had good success and what is nice you can remove the manifold without distroying the gasket and reuse it many times. When you use custom sheet metal manifolds or highly ported manifolds it saves a bunch of time and gasket mess making everything fit everytime you have to pull the manifold and reinstall. You run a coat hanger with a rag to mop up the excess silcone grease in the ports.
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Re: How to make sure a sb chevy intake will seal?

Postby GM-DR » Fri May 28, 2010 11:03 am

Are you sure you have enough clearence on the end rails? set manifold on with new gaskets ,No sealer, lightly snug bolts and slide A feeler gauge under front and rear. I would suggest .025 at minimum! Hope this helps.
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