2 1/4 exhaust slant 6

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Otateral

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I've been reading that 2 1/4 is the ideal size for these. Was just curious because the stock exhaust manifold is 2". Wouldn't that make the extra 1/4" ineffective?
 
Gasses expand as they cool, the temp of the gasses will only drop the farther they get from the engine, so..

I can't tell you what exhaust size is best for your setup but no, that won't make it ineffective. If you want to make the most of it, make sure you build the exhaust with mandrel bends and not some crushed and kinked muffler shop piping.
 
Don't think I'd spend the extra to get mandrel bends on the exhaust for my stock /6. JMO Doubt it would have a noticeable effect on my car anyway. Not sure of what the exact price difference is though.
 
With 2 1/4" pipe by the time you add a few bends (non mandrel bends) it's squeezed down to about 2", as long as the pipe isn't crushed on the bends it is about the right size for a slant 6. Mandrel bent exhaust is overkill for a slant 6. Anything is an improvement over the stock pee-shooter exhaust that is usually found on a slant 6.
 
I've been reading that 2 1/4 is the ideal size for these. Was just curious because the stock exhaust manifold is 2". Wouldn't that make the extra 1/4" ineffective?

I wouldn't know about ideal size or manifold size. My 73 came with a 1 7/8" exhaust pipe. The Feather Duster had a 2¼" exhaust system from head-to-tail. As far as I know the same exhaust manifold was used.

When I replaced the exhaust on the 73, I went to a 2¼" pipe. There was a slight improvement in mpg. The sound through a "turbo" muffler was a little bit deeper. To answer the question, I would say that the /6 responds favorably to the larger pipe.

The physics of the change suggest that there would be at least a little loss of scavenging due to the lower velocity through the larger pipe. I have no way to measure the difference, so at this point the difference is theoretical.

FWIW: A gas contracts as it cools not expands. (see Charles's Law). If this were not true, a lot of money has been wasted on ram air hoods and intercoolers.
 
i don't think the 2" outlet at the manifold will make much difference as it is just for a very small distance. on my 41 plymee , /6 i ran 2 1/4 right off the manifold, and all the way back. i have no complaints. currently in the process of splitting the manifold, and will be running dual 2 1/4 ahter that. can't wait to hear it.
 
I had my 65 Valiant Signet outfitted with 2.25 last year all the way through muffler to rear. Today I find that the first 4' off the manifold is less, maybe 1.75 or 2". The tech said he couldn't do 2.25 from the header. Can it be done and should I find another exhaust pro?
 
I had my 65 Valiant Signet outfitted with 2.25 last year all the way through muffler to rear. Today I find that the first 4' off the manifold is less, maybe 1.75 or 2". The tech said he couldn't do 2.25 from the header. Can it be done and should I find another exhaust pro?
Lazy, the easy way. No doubt it can be done.
 
I believe the Super Sixes came with a 2 1/4" factory from the manifold back. Not sure if the exhaust manifold is the same or different.
 
If I'm not mistaken, you can take a Dremel and open up the manifold to a 2-1/4" opening. And yes the exhaust "pro" is full of it, they were just too lazy to do things the right way.
 
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