67 - 68 BB Q-jet gasket - Chevelle Tech
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post #1 of 16 (permalink) Old Dec 3rd, 19, 1:31 PM Thread Starter
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67 - 68 BB Q-jet gasket

I was wondering what carburetor base gasket setup you guys are running that have a stock intake and Q-jet carb on their big blocks. Are you using just a gasket? or are you using the stainless plate and gasket? or gasket, plate, then second gasket? Also, have you pluged the hot slot holes in the intake manifold? or left them open? I am running hedders on my engine. Also concerned about exhaust heat crossover. Are you running restrictor plates on your intake gaskets? or leaving them wide open for max heat? I will be using my vehicle between 50 and 90 degrees. I am ready to bolt down my original restored 350hp intake manifold and could use some advice from anyone who has firsthand experience. Thank you,

Steve
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post #2 of 16 (permalink) Old Dec 3rd, 19, 2:39 PM
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Re: 67 - 68 BB Q-jet gasket

If you don't plug the holes under the carb, use a gasket,the sheet metal plate and then another gasket.


In regards to the exhaust crossover block plates,I can't really comment as I have mine blocked and I don't have a choke on my 780 cfm Holley.
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post #3 of 16 (permalink) Old Dec 3rd, 19, 4:10 PM Thread Starter
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Originally Posted by mr 4 speed View Post
If you don't plug the holes under the carb, use a gasket,the sheet metal plate and then another gasket.


In regards to the exhaust crossover block plates,I can't really comment as I have mine blocked and I don't have a choke on my 780 cfm Holley.
Did you plug the holes in yours? and what is your base gasket configuration?
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post #4 of 16 (permalink) Old Dec 7th, 19, 12:12 PM Thread Starter
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Come on now people, there's got to be some of you running a stock setup that has some information to share on this topic.
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post #5 of 16 (permalink) Old Dec 7th, 19, 1:36 PM
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Re: 67 - 68 BB Q-jet gasket

Mr. 4 Speed is right on about the gasket set up. I have a SBC, but for a BBC, I'm sure it's the same. From the intake up, it's the "asbestos style gasket" with the SLOT in it, the stainless steel heat shield, and finally a regular but thicker than normal carb gasket. Works great for me, and all the parts are available from Fel Pro at local parts stores. I run a Qjet in the middle of summer in 90+ degree heat and have never had a carb issue from it.
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post #6 of 16 (permalink) Old Dec 7th, 19, 2:18 PM Thread Starter
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Originally Posted by Buzzbomb View Post
Mr. 4 Speed is right on about the gasket set up. I have a SBC, but for a BBC, I'm sure it's the same. From the intake up, it's the "asbestos style gasket" with the SLOT in it, the stainless steel heat shield, and finally a regular but thicker than normal carb gasket. Works great for me, and all the parts are available from Fel Pro at local parts stores. I run a Qjet in the middle of summer in 90+ degree heat and have never had a carb issue from it.
Buzz, I agree with you guys. But I have plugged the two holes for the hot slot because of the poor design which led to Chevrolet discontinuing that design. I was hoping to hear from someone who has also plugged the holes and what gasket setup has worked for them. Can I get away with running a single gasket? Also who is running an open exhaust crossover on the intake to head gaskets and who is inserting the restrictor? and how is it working out for them in their climate? I guess there is just not that many of you running an aftermarket intake manifold with their Quadrajet carb.
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post #7 of 16 (permalink) Old Dec 7th, 19, 3:17 PM
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Re: 67 - 68 BB Q-jet gasket

Quote:
Originally Posted by 68elky396 View Post
Buzz, I agree with you guys. But I have plugged the two holes for the hot slot because of the poor design which led to Chevrolet discontinuing that design. I was hoping to hear from someone who has also plugged the holes and what gasket setup has worked for them. Can I get away with running a single gasket? Also who is running an open exhaust crossover on the intake to head gaskets and who is inserting the restrictor? and how is it working out for them in their climate? I guess there is just not that many of you running an aftermarket intake manifold with their Quadrajet carb.
As mentioned above, its the same for Holley equipped as it is for the Quadrajet. If you plug the holes, you can just run a regular gasket. Otherwise you have to block off the ports at the crossover. And don't think you can just slip a piece cut from an Aluminum Can in there....It won't last past the first startup, and if you have not plugged those holes, it will burn the aluminum base and warp it. I think the plug size is 7/16" cup plugs. You will still get heat, but it won't be jet blasted against the carb base plate, and no drilling involved.

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post #8 of 16 (permalink) Old Dec 7th, 19, 4:43 PM Thread Starter
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Quote:
Originally Posted by 68elky396 View Post
Buzz, I agree with you guys. But I have plugged the two holes for the hot slot because of the poor design which led to Chevrolet discontinuing that design. I was hoping to hear from someone who has also plugged the holes and what gasket setup has worked for them. Can I get away with running a single gasket? Also who is running an open exhaust crossover on the intake to head gaskets and who is inserting the restrictor? and how is it working out for them in their climate? I guess there is just not that many of you running an aftermarket intake manifold with their Quadrajet carb.
As mentioned above, its the same for Holley equipped as it is for the Quadrajet. If you plug the holes, you can just run a regular gasket. Otherwise you have to block off the ports at the crossover. And don't think you can just slip a piece cut from an Aluminum Can in there....It won't last past the first startup, and if you have not plugged those holes, it will burn the aluminum base and warp it. I think the plug size is 7/16" cup plugs. You will still get heat, but it won't be jet blasted against the carb base plate, and no drilling involved.
Langss, thanks for the response. I have already plugged the holes with 1/4" stainless pipe plugs. It sounds like I can just use a standard base gasket at this point. I'm just unsure about running the intake gaskets wide open at the exhaust crossover, or use the supplied restrictor plates to reduce the flow of hot exhaust gasses. I'm not sure how much heat the bottom of the intake needs in order to operate efficiently. The exhaust crossover is there to not only feed the hot slot, which I have plugged, but also to heat the manifold. Nobody seems to have any firsthand experience with this. To restrict or not restrict? It may depend on weather temps in which the car will be operated in, I don't know.

Steve
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post #9 of 16 (permalink) Old Dec 7th, 19, 8:51 PM
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Re: 67 - 68 BB Q-jet gasket

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Originally Posted by 68elky396 View Post
Langss, thanks for the response. I have already plugged the holes with 1/4" stainless pipe plugs. It sounds like I can just use a standard base gasket at this point. I'm just unsure about running the intake gaskets wide open at the exhaust crossover, or use the supplied restrictor plates to reduce the flow of hot exhaust gasses. I'm not sure how much heat the bottom of the intake needs in order to operate efficiently. The exhaust crossover is there to not only feed the hot slot, which I have plugged, but also to heat the manifold. Nobody seems to have any firsthand experience with this. To restrict or not restrict? It may depend on weather temps in which the car will be operated in, I don't know.

Steve
My car came from your neck of the woods, so the heat probably would have been beneficial. Living in California, not so much. All the cars I have worked on, I have used the stainless restrictor, at the crossover and even on the coldest days here....a couple of pumps(carb vehicles)and they always start right up and drive away, no problems. From a performance perspective, if your doing any street driving, limiting the exhaust gas would be all the farther I would go. When I bought my Chevelle, the spring on the Heat Riser, was weak, and the thing would clang like a bell. I wired it open and for the three months of UP weather I drove the car around in, I saw no difference. See the picture below, that was the first snow in October of 69, and right after I took the picture I had to move the car so the lot could be plowed....Started right up and drove away. I hope this helps.
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post #10 of 16 (permalink) Old Dec 7th, 19, 9:02 PM
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Re: 67 - 68 BB Q-jet gasket

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Originally Posted by 68elky396 View Post
Can I get away with running a single gasket?
No, the standard quadrajet intake gasket is 1/4" thick and is needed to insulate the heat.

Don't use a regular gasket that is thin (1/16" thick). The carb will overheat.

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post #11 of 16 (permalink) Old Dec 8th, 19, 8:15 AM Thread Starter
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Thank you lang and nashville for the advice. I am going to install the manifold today with the restrictors installed in the intake gaskets. I will also obtain a thick carburetor base gasket. I am running headers, so I do not have a heat riser in the exhaust system. Hopefully, this will not be a problem when restricting the exhaust crossover heat.

Steve
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post #12 of 16 (permalink) Old Dec 13th, 19, 11:51 AM Thread Starter
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Originally Posted by 68elky396 View Post
Thank you lang and nashville for the advice. I am going to install the manifold today with the restrictors installed in the intake gaskets. I will also obtain a thick carburetor base gasket. I am running headers, so I do not have a heat riser in the exhaust system. Hopefully, this will not be a problem when restricting the exhaust crossover heat.

Steve
O.K, life and work has been getting in the way of progress. I am bolting down the intake manifold today. I found these bolts that I had stored away in a baggie. Does anyone know if these look like the correct intake bolts for a 1968 396? The bolt head reads MANLEY5.

Steve
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post #13 of 16 (permalink) Old Dec 14th, 19, 11:22 PM
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Re: 67 - 68 BB Q-jet gasket

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Originally Posted by 68elky396 View Post
O.K, life and work has been getting in the way of progress. I am bolting down the intake manifold today. I found these bolts that I had stored away in a baggie. Does anyone know if these look like the correct intake bolts for a 1968 396? The bolt head reads MANLEY5.

Steve
Nope, never seen a factory intake bolt like that.

But if they are in good shape, paint the bolt heads to match the cast iron intake so they blend in.

Intake bolts are not stressed like other bolts. Nothing special needed.

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post #14 of 16 (permalink) Old Dec 15th, 19, 8:09 AM
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Re: 67 - 68 BB Q-jet gasket

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Originally Posted by 68elky396 View Post
? I guess there is just not that many of you running an aftermarket intake manifold with their Quadrajet carb.

Of course there are. I made a 1/2" phenolic spacer, and with that I 'll run a thin and thick base gasket, sandwiched similar to the "heat shield" setup GM used to sell. GMPP dual flange intake.

Steve, they have the correct flange tho. Run'em!

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post #15 of 16 (permalink) Old Dec 15th, 19, 8:44 AM Thread Starter
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Originally Posted by nashville beth View Post
Quote:
Originally Posted by 68elky396 View Post
O.K, life and work has been getting in the way of progress. I am bolting down the intake manifold today. I found these bolts that I had stored away in a baggie. Does anyone know if these look like the correct intake bolts for a 1968 396? The bolt head reads MANLEY5.

Steve
Nope, never seen a factory intake bolt like that.

But if they are in good shape, paint the bolt heads to match the cast iron intake so they blend in.

Intake bolts are not stressed like other bolts. Nothing special needed.
Thanks for chiming in nashville. I went ahead and used those bolts to install the intake, I may end up swapping them out if I locate the proper set, one at a time of course.

Steve
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