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Old 10-26-2007, 09:40 PM
hellbilly1932
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intake manifold questions

Do the exhaust gasses go throught the intake under the carb? like a preheat?
 
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Old 10-27-2007, 01:28 AM
pcmenten
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Yes. The rate of exhaust gas flow through the intake crossover is usually controlled by a valve between the exhaust manifolds where the exhaust crossover pipe connects the two exhaust manifolds (in a truck). By blocking the flow of exhaust through the exhaust crossover pipe, it caused the exhaust to flow through the intake manifold crossover. Once the engine warms up a bit, the valve opens up and the exhaust gas flows through the exhaust crossover pipe.

A relatively small area of the intake is warmed; right below the carb. Fuel that flows out of the carb wets this warm area and is then vaporized, making it burn clean and lean. Blocking off the the crossover passage in the intake is not a good idea if you drive in any kind of cold weather.

The crossover passage in the intake can get carboned up. I use lye (Red Devil drain cleaner) to dissolve the carbon build-up.
 

Last edited by pcmenten; 10-27-2007 at 01:30 AM. Reason: Clarity
  #3  
Old 10-27-2007, 01:32 AM
hellbilly1932
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will this cause any problems if the valve is not there on the crossover pipe.
 
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Old 10-27-2007, 02:02 AM
pcmenten
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Originally Posted by hellbilly1932
will this cause any problems if the valve is not there on the crossover pipe.
If you live in San Diego, no, it will not cause any serious problems. You might notice that your engine runs a little better after about a half hour of driving, but it should run fine in the warm weather of San Diego.
 
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Old 11-29-2007, 12:53 PM
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Originally Posted by pcmenten
Yes. The rate of exhaust gas flow through the intake crossover is usually controlled by a valve between the exhaust manifolds where the exhaust crossover pipe connects the two exhaust manifolds (in a truck). By blocking the flow of exhaust through the exhaust crossover pipe, it caused the exhaust to flow through the intake manifold crossover. Once the engine warms up a bit, the valve opens up and the exhaust gas flows through the exhaust crossover pipe.

A relatively small area of the intake is warmed; right below the carb. Fuel that flows out of the carb wets this warm area and is then vaporized, making it burn clean and lean. Blocking off the the crossover passage in the intake is not a good idea if you drive in any kind of cold weather.

The crossover passage in the intake can get carboned up. I use lye (Red Devil drain cleaner) to dissolve the carbon build-up.
I just replaced the original 292 in my recently acquired '64 F100 with a rebuilt 292. However, I decided to use headers instead of the stock exhaust manifolds and crossover pipe. I live in MN and plan to drive the truck during the winter. Are there things I should do to prevent issues?...should I expect issues in the first place? Thanks!
 
  #6  
Old 11-30-2007, 01:42 PM
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I ALWAYS block off the intake manifold heat riser port. First on a freshly painted engine the exhaust gasses will burn off the paint. Second heat under the carb robs horse power.

I use thin tin to block off this port to prevent any heat under the carb, yes it runs poorly when cold but I only drive it when its nice out!

Kevin Bigwin
 
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