Blocking intake exhaust crossover
Thread Starter
Instructor
Joined: Jul 2005
Posts: 228
Likes: 13
Blocking intake exhaust crossover
To prevent burning fresh paint off a small block intake, I'm considering blocking off the exhaust crossover passage. Other than affecting initial cold start-up performance, will there be any other side effects? At full temp/normal operating temp will the engine still run ok with normal fuel mileage etc? Thanks.
Le Mans Master
Joined: Mar 2008
Posts: 5,948
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From: Oxford MA-----You just lost the game!!!!
Ya know, when the timing is properly advanced, exhaust temps actually go down, because more of the combustion actually takes place inside the combustion chamber. How is your timing set up?
Keep the shiny side up!
Scott
Keep the shiny side up!
Scott
Team Owner
Joined: Jan 2006
Posts: 37,637
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From: Crossville TN
Other than taking longer for the carb to warm up and the choke to drop off, there is no downside to blocking off the intake crossover passage. (At least, I don't know of any.) If you don't drive that much in cold weather, block it off, if you want. The choke will still allow you to make cold starts, but the engine will be sluggish longer and you may have to 'kick off' the choke with the accelerator pedal, once the engine idle speed gets too high for your comfort.
Melting Slicks
Joined: Apr 2001
Posts: 3,399
Likes: 279
From: Olmsted Falls, Ohio
I think it comes down to what type of choke you have.
If electric, then no effect.
If hot air, with the tubes in the intake manifold (as a lot of C3s had) then they will not heat up as fast and you may have a problem with the choke not working like it did before.
FWIW: A high-temp rattle-can paint will not burn off the intake, even with the crossovers open.
If electric, then no effect.
If hot air, with the tubes in the intake manifold (as a lot of C3s had) then they will not heat up as fast and you may have a problem with the choke not working like it did before.
FWIW: A high-temp rattle-can paint will not burn off the intake, even with the crossovers open.
Last edited by KenSny; Sep 27, 2012 at 08:21 AM.
Burning Brakes
Joined: Feb 2005
Posts: 894
Likes: 91
Blocked Heat-Crossovers
What platform are you talking about, SB, BB, (oval/square)???
We block off almost all the units we build and haven't had a single customer complaint so far! It is a "non-issue" here and customer choice!
It is easily reversible with an intake gasket change!
Thanks, Gary in N.Y.
P.S. We use the "LPG" intake gaskets on these units. They aren't available for the BB square-ports however, on these we use "plates" with factory gaskets!
We block off almost all the units we build and haven't had a single customer complaint so far! It is a "non-issue" here and customer choice!
It is easily reversible with an intake gasket change!
Thanks, Gary in N.Y.
P.S. We use the "LPG" intake gaskets on these units. They aren't available for the BB square-ports however, on these we use "plates" with factory gaskets!
Team Owner
Joined: Jun 2000
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From: Southbound
Cruise-In II Veteran
Team Owner
Joined: Jan 2006
Posts: 37,637
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From: Crossville TN
Even 500*F paints will discolor and eventually flake off, if the crossover ports are left open. More capable paint will last...but who knows of a high temp paint that is made in Chevy Engine Orange?
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Melting Slicks
Joined: Mar 2005
Posts: 2,838
Likes: 10
From: Austin TX
As far as the choke, you can either lengthen or shorten the rod on the divorced choke set-up which will keep the choke closed for a longer period of time. Whether you shorten or lengthen the little rod depends on which choke set-up you have (what year). A new rod is very simple to fab with some 1/8" steel wire from Home Depot or anywhere.
Melting Slicks
Joined: Mar 2008
Posts: 2,023
Likes: 6
From: Austin Tx
If you want the paint to not discolor, you need to block off the crossovers.Also, if you have a divorced choke, it will take a while for the choke to open when it's cold. A simple solution is to purchase an electric divorced choke.
Scroll down towards the bottom - http://www.carburetion.com/quadrajet.asp
Drifting
Joined: Jul 2008
Posts: 1,483
Likes: 459
From: Lititz PA
Can someone please tell how they actually blocked off the crossover? Will some stainless steel shim stock work? Do you glue it somehow to the intake gasket?
Mine is a 454 with a Performer Intake with an electric choke.
Thanks,
John
Mine is a 454 with a Performer Intake with an electric choke.
Thanks,
John
Safety Car
Joined: Oct 2000
Posts: 3,593
Likes: 103
From: Southern Indiana
I have an "RPM style" intake with no crossover and no choke and it takes awhile to warm the engine up but the carb never gets hot.
On a regular intake with a crossover "they" used to use squares cut out of an aluminum can and just put the gaskets then the squares then the intake and it blocked the heat, I don't know if it ever burnt thru or not?
On a regular intake with a crossover "they" used to use squares cut out of an aluminum can and just put the gaskets then the squares then the intake and it blocked the heat, I don't know if it ever burnt thru or not?
Melting Slicks
Joined: Apr 2001
Posts: 3,399
Likes: 279
From: Olmsted Falls, Ohio
SHERWIN WILLIAMS Automotive GBP #988 Self Etching Primer
DUPLI-COLOR Engine Enamel Chevrolet Orange #DE1620
on my iron intake it is still nice after 10+ years. Media blasted the outside first then painted.
Team Owner
Joined: Jul 1999
Posts: 65,492
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From: Orange Park Florida
Those block off inserts and gaskets are useless, seen them burn through pretty quickly....
Drifting
Joined: Jul 2008
Posts: 1,483
Likes: 459
From: Lititz PA
BTW, the proper way to block it off is to get some Plaster of Paris at Lowes Depot and tape off one side, tip the intake on end and pour the thick liquid into the passage and let set up overnight.....
Those block off inserts and gaskets are useless, seen them burn through pretty quickly....
Those block off inserts and gaskets are useless, seen them burn through pretty quickly....
John
Safety Car
Joined: Sep 1999
Posts: 4,930
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From: AnyTown NJ
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
That's the best way....
I just wired my heat riser valve open which helps with the paint discoloration.
Race Director
Joined: Jan 2000
Posts: 12,399
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From: San Jose CA
I'm sure between the cylinder heads, coolant, and oil splashing along the bottom, it'll warm up. Not to mention numerous heads and intake don't have these crossovers at all (including some OEM TBI setups which are still wet manifolds).