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  #1  
Old 11-25-2005, 01:56 AM
michaelmopar michaelmopar is offline
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Default Exhaust!!!!

I have headers going into 21/4" going into a y to 3" into one flowmaster 3" in and 3" out two chamber. I was told by DB that i would pick up some torque and others told me it would hurt my performance. Does anyone have anymore input on this matter. The SB Mpar is a mild build and is soon to have a demonizzer tq on it.
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Old 11-25-2005, 06:34 AM
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Eggman Eggman is offline
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I have a similar set up on my truck.Headers into 2.25 Y with a 3.00 outlet.I am using a Hooker Aerochamber muffler center in, center out with a 3 inch pipe exiting in front of rear tire.I don't have any performance problems and do not plan to change it.
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  #3  
Old 11-25-2005, 10:00 AM
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ehostler ehostler is offline
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OK, you didn't mention the size of your primaries.

From the what you have described, you are going to kill your low end. You have removed most (if not all) of your back pressure. With proper back pressure, the exhaust flow picks up velocity, this velocity creates a vacuum and helps to remove more of the exhasut gases from the cylinders.
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Old 11-25-2005, 12:04 PM
michaelmopar michaelmopar is offline
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ok sounds great any suggestions a 4 inch pipe or just not a 3 inch or what my primaries r 1 5/8. so "E" what do you suggest? go to a 4 inch single? i dont have room under the truck to run two turbo mufflers side by side unless i turn them on their side. I guess you or anyone else would know this problem with dodges the gas tank is in the way. so you have to either run single or run glasspack which i hate.
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  #5  
Old 11-25-2005, 12:59 PM
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ehostler ehostler is offline
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At minimum, I would use step headers.
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  #6  
Old 11-25-2005, 03:25 PM
TK TK is offline
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I would leave it alone, with 1 5/8 primary's, going into a 3" with 2 1/4", you should be just fine.
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  #7  
Old 11-25-2005, 03:44 PM
rusty duster rusty duster is offline
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Quote:
Originally Posted by ehostler
OK, you didn't mention the size of your primaries.

From the what you have described, you are going to kill your low end. You have removed most (if not all) of your back pressure. With proper back pressure, the exhaust flow picks up velocity, this velocity creates a vacuum and helps to remove more of the exhasut gases from the cylinders.
So what you are saying is the law thats applies to a liquid or a gas that says if you speed up a gas its pressure decreaces is wrong?How can back pressure speed up a gas inside a pipe?Now if you are talking reversion waves that travel back and forth because of the valves opening and closing that is something else.I think that all the muffler companies that pay for articles in a car mag that say a muffler is better than an open pipe is bogus.Its my thinking that any back pressure at all will hinder flow.
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  #8  
Old 11-25-2005, 05:20 PM
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pishta pishta is offline
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Rusty, They sell port restrictors for 351C 4v's exhaust for this exact reason.
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  #9  
Old 11-25-2005, 06:07 PM
TK TK is offline
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Seen a 4BBL Cleveland head latley?

The single exaust will make good backpressure, and keep it hotter. His exaust is fine.
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  #10  
Old 11-25-2005, 11:56 PM
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pishta pishta is offline
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Yeah, in my garage...set of Aussie and US models...Its a wonder that these idled at all.
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  #11  
Old 11-26-2005, 12:10 AM
Tarrbabe Tarrbabe is offline
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Default Sounds good to me........

I have never seen it but have read about this before. Anyone remember all the factory systems that went from 2 pipes to one muff and one larger ex pipe?
This is the set-up on the commaro's as well as a lot of Mope's. The late 70's model's Mopars Cop Cars had this set-up The larger pipe just allows for better flow when needed. The combining of the pipes to one you still get back pressure but with a little loss due to the larger size.
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  #12  
Old 11-26-2005, 12:30 AM
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Pishta - Just got rid of some Oz 4bbl Cleveland heads that my late Father had once planned on using in an altered (the one I'm using as my avatar. Don't worry - he saw the light and went with a 360). I know what you mean - I'd forgotten just how big the ports were on the damned things. Never understood Ford guys - with those things available, why would you mess with Windsors?
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  #13  
Old 11-26-2005, 01:40 AM
TK TK is offline
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Because a 4bbl cleveland wasn't any good untill 5000 or so. Ports were way too big.
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  #14  
Old 11-26-2005, 01:45 AM
party340 party340 is offline
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Rusty duster, a 2.5 pipe does not have back pressure at low engine speeds, not enough exaust gas there. The exaust gas is moving faster in a 2.5 pipe than a 3 inch pipe. The high speed creates a vaccume in the exaust port because of its inertia. This vaccume also helps pull intake charge during overlap (when the intake and exaust valves are open at the same time. At higher engine speed, the 2.5 pipe would produce back pressure and would hurt high end performance. Here a 3 inch pipe would have enough gas to speed up velocity. At low rpm the 3 inch pipe exaust gases have a low velocity. This does not create vaccume in the chamber. Instead, during overlap, the slow moving exaust gas may actually be pulled back in the chamber with the fresh intake charge.
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  #15  
Old 11-26-2005, 02:22 AM
TK TK is offline
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Not with the 2 1/4" pipes before the 3" That is where your velocity will be.
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