Exhaust Diameter vs engine power

jtwoods4

Member
Mar 19, 2010
53
Atlanta, Ga.
As the size of the exhaust system increases does the engine gain or lose power? For example, I have an L34 396 V8, what effects does a 2.5 inch vs 3.0 inch exhaust have on the engine performance/power/etc....
 

dcozzi

Veteran Member
May 1, 2002
4,496
Phoenix, AZ
Bigger exhaust supports more power but there is a point of diminishing return.
You start to lose lowend torque when header primaries are too big and when the rest of the exhaust flows too freely as well. The cam profile also has a big effect on this. Lots of variables to think about.

As a general rule, I like to think 2.5" all the way back to the rear bumper is good up to 500HP. After that, 3" can give you noticeable gains.

Some people say 550HP is where you should start using 3". I had 523HP at the crank on a 406" motor and going from 2.5" to 3" made a difference. Sounds waaayyy cooler too.
 

76z28

Veteran Member
Jun 29, 2009
2,541
bakersfield
3 inch will give you more top end
DEPENDING ON APPLICATION
2.5 is the way to go though
that is what i just put on mine SOUNDS AWESOME
 

jtwoods4

Member
Mar 19, 2010
53
Atlanta, Ga.
I bought the car with 3 inch exhaust so I am wondering if I will get better performance with 2.5 inch, I am changing the CAM back to almost stock (little bigger) from the massive thumper that is in there now. 396 engine
 

NYH1

Veteran Member
Feb 27, 2010
1,604
Central New Yorkistan
Are you going to keep the 396 in the car? Or do you plan on putting a higher power 454, 496 or 502 in it sometime down the road?

If it were me and I was going to keep the mild 396 in it, I'd go with 1 3/4" full length headers and a 2.5" full length dual exhaust system. There are a bunch of difference exhaust systems out there for gen II Camaros. I went with the Flowmaster system that uses the transverse muffler. It sounds great and has a lot more ground clearance.
 

Rick WI

Veteran Member
Jul 9, 2001
10,400
Madison, WI
Restriction is lost power. Tailpipes especially are a power grabber. You really can't have too big of an exhaust, just poor tuning and lack of space.
 




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