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Discussion Starter #1
Hey guys, I currently have 2 1/4" flowmaster exhaust on my 68' and I was gonna get a new 2.5" or 3" system. What are some of the best systems that are out there and whats the benefit to having a 3" rather than a 2.5" system?

Ive heard Pypes and dynomax thrown around, but what do you all think?
 

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The "benefit" of a 3-inch system over a 2.5-inch system is, unless you're making 550 HP or better you're going to LOSE low-rpm torque and responsiveness. :D

It happens because the larger pipes result in reduced flow velocity - reduced velocity translates into less inertia of the moving exhaust gas column - less inertia means the motor has to expend energy to PUSH the gas through the pipe instead of it's own momentum tending to "pull" it out - energy that could have othewise been used to propel the car.

Bigger is NOT always better.

Bear
 

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stay 2.5. I have 2.5 on my 700 hp car and it's not choking it down at all...dyno tested...I'll see if I can find the comparison dynos for it.

2.5 go with a chambered 40 series or similar. I've heard good things about pypes as well. magnaflow is nice, but a touch pricey.
 

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Discussion Starter #5
Thanks for the info guys. I know bigger is not always better but Ive seen alot of 3" systems for sale. Looks like Ill be going with 2.5" Pypes system most likely.
 

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I installed the 2.5" American Thunder system from Flowmaster years ago in my 69 Goat, and have re-installed it this summer during a frame-off resto. I couldn't be happier with it.
 

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Here are the two kits Magnaflow offers. There are options for a 2.5" and 3.0" systems. If you go to www.magnaflow.com there are also sound clips available.


Year Description Type Image Part # MSRP

1968 V8 6.6L; 400 CID
4 x 9 x 14in. Muffler; 2.5in. Tubing; 2.5in. Turndown; EXIT OPTIONS Crossmember-Back 15894
1968 V8 6.6L; 400 CID
4 x 9 x 14in. Muffler; 3.0in. Tubing; DUAL SPLIT REAR SIDE EXIT Crossmember-Back 15898


http://www.magnaflow.com/02product/shopdisplayproducts_cars.asp?make=PONTIAC&model=GTO&year=1968
 
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