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Discussion Starter #1
at what power level do you need a 3" exhaust? I'm currently runing the bbk 1 3/4 long tube with off road h pipe. 2.5" exhaust 2 chamber flowmaster. my combo . 347 , stage 3 canfield, victor 5.0, custom blower cam. novi2000 18psi. 75lb injectors, pms. will a 3" exhaust made a big different? how loud is the 3" exhaust?
 

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I have read that at about 600 fwhp is a good time to move to a 3 in. exhaust. In your case, i am sure you are making at least that, so it should benefit you.

You might want to measure the collector diameter on those bbk long tubes you have. I have heard that they aren't the advertised 3 in. diameter. I know a guy that has those and he had the person who built his exhaust cut off the collectors and put on real 3 in. ones. His name is neagrouptim on the corral.
 

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Loi,

I have the same headers and the collectors are only 2 1/4" at best. You will definitely need 3" exhaust for your power level. You could weld true 3" collectors on them w/3" X or H-pipe. As for HP levels, it is different for forced induction and N/A. N/A requires 3" exhaust at a much lower power level for max HP gain. Close to 450 fwhp. I am going to a stepped header (1 3/4- 1 7/8" primary) and 3" collector w/3" X-pipe from Kooks. I just talked with George Kook Jr yesterday regarding this very subject.

Andy
 

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I agree that a 3" exhaust setup would help performance but those dinky collectors gotta go.

3" exhaust will be louder than 2 1/2" so be prepared. X pipe would help quiet it down a bit.
 

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I run a mac 3" cat back and it fits great and sounds good too. It doesn't have the "normal" mustang sound. I think you need a 3" exhaust when your trying to push into the 10's like me. My BBK headers are 1 3/4" but HAVE a 3" collector, maybe because they are for a 351?

All Motor!
 

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Discussion Starter #7
lx4play, let me know what you end up running. mac does made just a 3" collector , if i changed the collector i will have to run the 3" x pipe? my 2.5 bbk is useless then. my question is does it worth the hp level switching from a 2.5 to 3" have anyone done any testing?

john91, what exhaust system do you run?

long stroke, I'm hoping to push into the 9s lol , i check with bbk, they said the 1 3/4 long tube only come with a 2.5" collector, are you sure those are not custom?

az50h, you are right, bbk LT only came with 2.5" collector
 

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exhaust

I talked ot MAC about this last week and dude said that it was recommended to run a smaller collector with the 3" exhaust. He babbled on about expansion theory or some crap, anyway I just thought I'd throw that in!
 

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john91, what exhaust system do you run?
Mine has Kook's 2" primary tubes with 3 1/2" collectors. X pipe is 3 1/2" Dr. Gas and 3 1/2" Hooker Aero Chamber mufflers.

I talked ot MAC about this last week and dude said that it was recommended to run a smaller collector with the 3" exhaust. He babbled on about expansion theory or some crap, anyway I just thought I'd throw that in!
That's kinda funny. There actually are collector designs that neck down in some specific applications (Kook's makes them). They are far different than the type of collectors that are on MAC's though. Sounds like he's trying to capitalize on that design even though they don't actually have it.
 

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the 450fwhp n/a/600forced is about right,

the mac 3"catback fits great

if I were you I'd prolly run mac evrything, 13/4lt's w/3"collector, 3"powerchamber(better and quieter than X),3" catback

I always thought it was bettter to have collectors 1/4-1/2" larger than your exhaust
 

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Discussion Starter #11
does mac made a shorties 3" h pipe? with the matching 3" exhaust?
 

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loi said:
does mac made a shorties 3" h pipe? with the matching 3" exhaust?
Yes, they do.
 
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