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Unread 05-01-2013, 04:44 PM   #46
swatson454
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1983 CJ7 
 
Join Date: May 2009
Location: Dripping Springs, TX (soon)
Posts: 4,497
Quote:
Originally Posted by pman View Post
More backpressure?
It's never, ever beneficial to have back pressure. The only useful purpose back pressure has is spinning a turbo

I do, however, have a theory () after some consideration. The exhaust flow and maybe even pressure waves (assuming they don't cancel each other out in that cluster *&%# manifold; which is about 99.9% likely) from one bank will hit the merge collector and produce a siphon effect, similar to the ported vacuum aperture in a carb venturi, and help draw from the other side of the merge collector.

Manifolds create nothing but a pressure system with no functional wave tuning so air flow through the merge is the only energy I can think of to harness.

I'm supposed to talk to a buddy of mine here pretty soon so I'll try to remember and see if he's done any testing on it and if he has any thoughts.


Shawn

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Unread 05-01-2013, 05:50 PM   #47
jeepdaddy2000
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1971 CJ5 
 
Join Date: Jan 2002
Location: Eagle Point Oregon
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Quote:
Originally Posted by Matt1981CJ7 View Post
Jeepdaddy,

Something like this?

Matt
Winner, winner, chicken dinner.....

As far as back pressure is concerned, slight back pressure down low helps with low end torque. Of course, removing a stock restrictive single pipe and replacing it with headers will show larger gains as will replacing it with a solid dual exhaust with the right size tailpipe. In that case however, most notable gains with the headers will be in the upper end and will be dependent on other upgrades as well.

Dual exhausts are routinely connected via a crossover pipe (or X pipe) to help smooth pulses and equalize the pipes, which helps scavenging. Unfortunately, Jeeps have a limited amount of room underneath, which forces many of these upgrades, which are routinely found on cars, out of the picture.

On cars, headers last much longer, and have fewer problems. However, Jeeps routinely experience a lot of twist and flex, as well as vibration, extremes of hot and cold, rock strikes, broken hangers, and a plethora of other stresses not seen on street cars. These generally add up to more problems and a shortened header life.
I run headers on my CJ, but it is because it is about the only way to effectively route the exhaust and allow for the
Saginaw steering upgrade. I have been through two sets and if it were cheap and easy, I would return to stock manifolds in a heart beat.
In the end, there are just as many folks running headers as there are manifolds. Both sides (that are happy with their setup) will argue their point. That is the nature of a forum. To get opposing sides of modification. No reason for anybody to get excited or take anything personally. If the OP decides to go with headers, well, good for him. I wish him the best of luck......
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Unread 05-01-2013, 08:54 PM   #48
tchimmerroks
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1981 CJ5 
 
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Location: Grand Junction, Colorado
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Quote:
Originally Posted by Keith_b00ne View Post
I am interesting in getting some personal opinions from those that switched from a stock exhaust manifold to headers on a AMC 304. In particular: Did they fit well? What did you think of the power improvement? Any brands you would steer away from? Any durability issues? Any comments are welcome.
Years ago I owned a '78, 304 equipped CJ5 and I ran it with both headers and stock exhaust system (first headers). I much preferred the completely stock system. BTW, if you choose to go w/headers and you don't plan to keep your stock manifolds, I'd be very interested in buying them.
Thanks, Tim
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Unread 05-01-2013, 09:05 PM   #49
Alex77cj7
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1977 CJ7 
 
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Quote:
Originally Posted by tchimmerroks

Years ago I owned a '78, 304 equipped CJ5 and I ran it with both headers and stock exhaust system (first headers). I much preferred the completely stock system. BTW, if you choose to go w/headers and you don't plan to keep your stock manifolds, I'd be very interested in buying them.
Thanks, Tim
I was planning on getting rid of mine.
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