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Post Info TOPIC: Carb base heat cross over passage ways


Poncho Master!

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Carb base heat cross over passage ways


Has anyone here ever plugged off the Carb base heat crossover passage ways on a '68 327 with 4 barrel manifold. The '68 has exhaust running right under the front of the carb. And that gasket can burn out making like a permanent open EGR. If someone has done it, what was used to plug the holes? Pound in plugs or tap and screw in a plug? Also any drivability issues? It's a convertible so very little cold weather driving. 



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'68 Parisienne 2+2 Convertible Matador Red (Resale Red but not for sale).



Poncho Master!

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image.jpg



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'68 Parisienne 2+2 Convertible Matador Red (Resale Red but not for sale).



A Poncho Legend!

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I haven't done it but I saw one that someone had tapped and put allen head plugs into it. That looks the same as the 66 setup. I've never had a gasket burn on one of those. You are using the tin shield and the gasket with quite a bit of metal in the gasket material?

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1966 Strato Chief 2 door sedan 283 "survivor"


Poncho Master!

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I know why it burnt. Had a thick base gasket on top of the tin shield on top of the high temp gasket. So not enough sealing pressure on the tin shield. I didn't think the tin shield would seal against the carb.

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'68 Parisienne 2+2 Convertible Matador Red (Resale Red but not for sale).



Poncho Master!

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do it all the time, doesn't need to work under the carb, the crossover still works under the intake, and it works just fine in the winter at 40 below. I just use a couple of long bolts and tap them in cat them off at the top you can use some epoxy if you want but they will carbon in over time.just make sure they bottom out in the intake don't put sort ones in. long cant come out. I also use a plastic insulator works better speed shops sell them, along with different tin plates.



-- Edited by 65wagon on Thursday 16th of August 2018 12:09:11 AM

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A Poncho Legend!

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JC2+2 wrote:

I know why it burnt. Had a thick base gasket on top of the tin shield on top of the high temp gasket. So not enough sealing pressure on the tin shield. I didn't think the tin shield would seal against the carb.





I've always marveled at how that tin shield works on the carb, but it does!

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1966 Strato Chief 2 door sedan 283 "survivor"


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Hope this is what your asking. Have always blocked off the cross over at the manifold. Only drive in the summer and doesn't discolor the intake. Been a while but used to get the intake gaskets for a 283 with the tin insert with a round knockout in it. If you wanted the heat cross over you'd knock out the round hole on the block off. Not sure if they still make them that way. But found something close on line, mind you this would prevent the choke from working properly.....but I always warm mine up by throtle manually anyways and choke is set open cold.
1957-1965 Corvette FI Intake Manifold Heat Riser Block-Off Plates



-- Edited by hawkeye5766 on Thursday 16th of August 2018 02:56:19 AM

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Addicted!

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Go to google and search

Lars sbc gasket fix

he gives the parts numbers of the

3 gaskets you need to put this together 

I did this and have no problems 

I have also heard guys drill and tap  for pipe plugs

Your choice

both work well



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67 Parisienne Convertible 



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Just spent half an hour reading through Lars sbc gasket fix
Dont have the carb but sure was fascinating reading all of the responses. This fellow is well respected in his field and extremely knowledgeable.

A great read if you have time.
Cliff

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Cliff

 

 



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Over the many years of owning small block Chevy's, i have always used the intake manifold gasket sets that have the built in metal block offs. Obviously only on engines that are just used in the summer months. They are extra cost but worth it. I like to keep my intakes looking good with out all that nasty rust that comes with the heat cross over. 



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1957 Pontiac Pathfinder Deluxe sedan restored 261 six

1974 Chevrolet Caprice Estate wagon low milage original 400 V-8



Poncho Master!

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you do need heat under the intake to vaporize fuel, you can block off the one side with out the choke , but it will still burn paint, its a trade off, I find the cross over under the carb gets the carb with our crap fuel too hot especially quads. im running aluminium intakes and leave the cross over open but insulated the carb with a plastic spacer.



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Poncho Master!

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I did some reading on that other site and decided to go ahead and plug the holes off. With the holes at 7/16" it was a natural to tap to 1/2 NC. I tapped down approximately 1" from the machined surface. Then made up a couple 1/2 NC set screws 3/4" long. (You could probably buy them as well) Then I bottomed them out with high temp thread sealer. I can now stack a regular carb base gasket over the original tin shield and gasket which now just seal vaccume. I never got a chance to road test but after idling for a while, it didn't seem to perculate in the carb on shutdown like it used to but I'll have to get it warned up good on a road test. Here's a few photos. Not in order of course. 



-- Edited by JC2+2 on Thursday 16th of August 2018 11:21:12 PM

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'68 Parisienne 2+2 Convertible Matador Red (Resale Red but not for sale).



Poncho Master!

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with the old set up my 400 would empty its fuel bowl, switched over to a thick spacer and a heat shield problem gone, it only happened once with winter gas in the tank



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Bump for norontcan



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67 Parisienne Convertible 



Canadian Poncho Superstar!

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SGS Welding wrote:

Bump for norontcan


 Thanks, I'm having my Quadrajet 4MV rebuilt so figured I'd look into this at the same time.



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Poncho Master!

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I'm sure you know this, but they came with the asbestos type gasket on the intake with the metal shield on top.

No gasket between the metal shield and the carb, especially not the one pictured!!.

Thanks
Randy


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A Poncho Legend!

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I've never been able to understand how a tin plate sealed a carb base but it did...

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1966 Strato Chief 2 door sedan 283 "survivor"


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Very interesting and informative read. I need to talk to my rebuilder.

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