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Rochchester Quadrajet carb to manifold gasket

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Old 04-04-2006, 05:30 PM   #1
njcardave
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Default Rochchester Quadrajet carb to manifold gasket

I want to know what type of carburetor gasket to use with the divided plenum Edelbrock performer intake manifold. Should I use a gasket that just sits on the outer edge of the carb mounting flange on the intake manifold and has no gasket on the edge that divides the plenum in half or whould it be better to use the factory gasket that has the four holes cut in it for the carb butterflies? The factory gasket would seal the space between the plenum divider and the bottom of the carb.
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Old 04-04-2006, 06:04 PM   #2
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Quote:
Originally Posted by njcardave
I want to know what type of carburetor gasket to use with the divided plenum Edelbrock performer intake manifold. Should I use a gasket that just sits on the outer edge of the carb mounting flange on the intake manifold and has no gasket on the edge that divides the plenum in half or whould it be better to use the factory gasket that has the four holes cut in it for the carb butterflies? The factory gasket would seal the space between the plenum divider and the bottom of the carb.
Use the former. Don't worry about the plenum divider.
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Old 04-04-2006, 07:25 PM   #3
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Don't use the one with the four holes in it. Use the one that has the big opening.
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Old 04-04-2006, 07:27 PM   #4
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Old 04-04-2006, 08:18 PM   #5
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Depending on the carb. you could try both. Mine with a q-jet wouldn't run right without the divided 4-hole q-jet gasket. With the Demon it also wouldn't run right wothout a 4-hole gasket. Even the gasket that the Demon came with, and the instructions say not to use any other, didn't work. Called tech. and they suggested to try a 4-hole, and it took right off. The tech told me that some motors reverberate back and forth between the two sides of the manifold under the carb otherwise. Some like it, some don't. Good luck, good thing it's not very expensive to try both ways.
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Old 04-04-2006, 08:19 PM   #6
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My suggestion is while you have the Q-Jet unbolted, buy a new holley carb.
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Old 04-04-2006, 10:02 PM   #7
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I just installed an Edelbrock Performer and a JET Stage 1 Q-Jet. My Q-Jet came with a gasket that DID NOT have the 4 holes and it runs good. Now that I think about it the old Q-Jet had a gasket that did not have the 4 holes either. hmmm. Make sure you properly torque the carb to specs - all bolts evenly.
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Old 04-05-2006, 01:16 AM   #8
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Quote:
Originally Posted by rrhodes4
My suggestion is while you have the Q-Jet unbolted, buy a new holley carb.
Don't let Lars hear you say that...

Besides, why should we replace our 750 CFM Rochester Q-Jets with a 600 or 650 CFM Holley? Finding a 750 CFM Holley is going to be twice as much as a good rebuild on our Rochesters.
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Old 04-05-2006, 10:36 AM   #9
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Quote:
Originally Posted by Sprzout
Don't let Lars hear you say that...

Besides, why should we replace our 750 CFM Rochester Q-Jets with a 600 or 650 CFM Holley? Finding a 750 CFM Holley is going to be twice as much as a good rebuild on our Rochesters.
I know, I know!!! I do agree that a Q-jet in prime condition I wouldn't change. But there are a ton of horror stories about rebuilds on them. Mine needed to be rebuilt and I found that the best alternative to it was the Holley 0-80555S. $325.00 AND NO WORRIES. A stock or slightley modified 350 engine doesn't handle a 750 cfm very well. Also I never called the Q-jet by its other name. The respect is there.
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Old 04-05-2006, 11:40 AM   #10
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Quote:
Originally Posted by njcardave
I want to know what type of carburetor gasket to use with the divided plenum Edelbrock performer intake manifold. Should I use a gasket that just sits on the outer edge of the carb mounting flange on the intake manifold and has no gasket on the edge that divides the plenum in half or whould it be better to use the factory gasket that has the four holes cut in it for the carb butterflies? The factory gasket would seal the space between the plenum divider and the bottom of the carb.

you will need the 4 hole gasket if you intend to use the original heat sheild, which i reccomend , but may not be required

.02


tim
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Old 04-05-2006, 02:16 PM   #11
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While we're talking about carb gaskets, Is there suppose to be more than just the 1/4" thick gasket between the carb and manifold?
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Old 04-05-2006, 02:23 PM   #12
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Quote:
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While we're talking about carb gaskets, Is there suppose to be more than just the 1/4" thick gasket between the carb and manifold?
Yes depending on the year there is a metal plate withthe same shape as the 4 hole gasket, called the Q-jet heat sheild originally used for all 1968-69 Corvettes with Rochester Q-Jet. The shield is supposed to be installed between the carburetor base and the gasket (i.e. on TOP of the gasket).

The shield is EXTREMELY important if the car remains equipped with an un-plugged heat groove on the forward part of the manifold carb flange. If you look at the carb flange on the manifold you will note this groove. At each end of the groove will be holes that connect the groove with the manifold's heat cross-over passage. Check the holes to see if they have been previously plugged with pipe plugs or cup-type plugs. If they have not been plugged, I strongly recommend that you do so. The easiest way to do this is to obtain some 3/8" cup-type plugs (mini "freeze plugs") that you can purchase at auto supply stores. Simply drive the plugs into the holes with the cup side up. This eliminates the heat groove functionality and will preservce the life of your carburetor without causing any detrimental effect. The heat groove causes the transfer of so much heat to the carburetor, even with the stainless steel heat shield installed, that carb throttle bodies and float bowls are often warped. GM eliminated this feature after 1969.

tim
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