Question regarding custom dual exhaust

32special

Active Member
So i finished drawing out the exhaust manifold flanges for my 263, and I know this has been asked but I just cant find it. Ill be running a factory dual compound set up wich leaves me asking. How should I supply heat to the two intake? If tubing or hose is used, how thick? I thought about making a plate that bolts underneath with a threaded stud sticking out to screw eather a hose, tubing or something. Not too sure, so thought I'd ask for opinions.
I thought about the engine coolant but dont want to risk eating away the cast iron. So back to exhaust heat. Are there pros and cons to each? If I remember correct, the chevy 6 had an after market intake that used coolant to warm it up.
eventually ill be runing a cast aluminum 4x2 intake warmed with that same engine coolant thru means of a passage way underneath with the coolant running straight thru one end, out the other and back to the circle.
 

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If you are going to run the factory 2X4 manifold and wish to heat the intake, why don't you want to just run the heat riser?

No coolant is required to the intake. "Heat" (from the exhaust) is supplied to warm the underside of the carburetor to enable smooth running at start up. Many performance installations block off this feature and remove the heat riser to keep the carburetor and intake cooler for a denser charge. It does cause an engine which has a tough time idling for a couple of minutes.
 

32special

Active Member
heat risers

All I obtained was the factory 2x2 with everything except the heat risers and dual exhaust manifold's. The 2x4 intake I still have to make a pattern and cast. Seems the only way would be to run a line from the exhaust to the bottom of the intake to warm the carbs. Still, no heat riser. How thick of a line should I run?
 
I think you are probably on your own for design. Most carbs are heated with a heat riser forcing the exhaust under the carb for the first few minutes after the car has started then opening to minimize the heat that the carb is being exposed to, and you are exploring a relatively unusual approach. I think you may have difficulty not using a heat riser which forces the high heat of the exhaust necessary to accomplish the job directly under the carb during the initial start up. I don't think this can be accomplished with coolant (which will be cold during start up), nor a passive tube running to the underside of the carb because it will not carry enough exhaust flow to accomplish the job properly.

Most people doing as you are would simply build a performance manifold without heat and live with the few minutes of bad idle when starting the cold motor, I know that is what I would do (but as mentioned, I am the type that blocks off heat crossovers and eliminates heat risers).
 
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32special

Active Member
exhaust heat

So be it. No need to break my canuck over a few minutes of turbulence. On the subject Bob. If I wanted to make a 3x2 too perfom better than a log, something like the 41-42 compound set up were each carb takes care of certain cylinders. How would I go in my case with the 3x2? Also, the log will have the small base for one primary and three secondary carbs retaining to the factory 41-42 set-up. Could the sec. Carbs be ran with out the bottom valve body(forgot its name) with the round counterweight on one side? Hope im not a pain Bob, but I have everything down except some math..lol. im really fascinated with those Carter carbs and insist on having to use them.
Im going to cast the log first since it takes one core and I know the 3x2 will be a bit more Intresting, just cant know so till I have the secret formula. This patter making is more work than I anticipated, at least for this newb to foundry work.
Thanks Bob





I think you are probably on your own for design. Most carbs are heated with a heat riser forcing the exhaust under the carb for the first few minutes after the car has started then opening to minimize the heat that the carb is being exposed to, and you are exploring a relatively unusual approach. I think you may have difficulty not using a heat riser which forces the high heat of the exhaust necessary to accomplish the job directly under the carb during the initial start up. I don't think this can be accomplished with coolant (which will be cold during start up), nor a passive tube running to the underside of the carb because it will not carry enough exhaust flow to accomplish the job properly.

Most people doing as you are would simply build a performance manifold without heat and live with the few minutes of bad idle when starting the cold motor, I know that is what I would do (but as mentioned, I am the type that blocks off heat crossovers and eliminates heat risers).
 
I am not clear on your questions. I am also not an expert. The reason 2x2 and 4x2 carbs work on the the I8 is that there are 4 intakes on the head. I don't believe they are run on a progressive linkage. The 4x2 carbs are a race set up and economy is not a concern, hence no progressive linkage required.

3x2 carbs are usually run on a progressive linkage as a good street setup. The center carb is run normally and the outer two pulled in on high demand. The 2x2 and 4x2 setups on the I8 overcomes the problem of different runner lengths found when running a single carb quite nicely. That is why they are popular. That does not mean 3x2 is not good, but it starts to introduce the runner length issue again.

Good luck with the project and please keep us posted!:thumbsup:
 
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