3 inch or 2.5 inch exhaust - Lateral-g Forums

akrapovic · #1 09-13-2007, 07:51 AM

I've received conflicting advice. I have a 396/402 BB, I've been told 3 inch is the only way to go for a BB. Others have said 2.5 in for correct back pressure.

Thanks in advance.

**XcYZ** · #2 09-13-2007, 08:08 AM

For performance, 3" without a doubt.

70gotboost · #3 09-13-2007, 11:40 AM

I was "told"... more than 383 ci, go with 3". Or ANYTHING supercharged/turbocharged needs 3".

jski67 · #4 09-13-2007, 12:17 PM

I've also read that 3 inch to the mufflers with 2.5 tailpipes is fine.

Supposedly, flow isn't affected much by the smaller pipe after the mufflers and 2.5 is a lot easier to bend and package.

I've got a tri 4-bar in my car, so I may go this route...

Jason

rocketman · #5 10-07-2007, 05:43 PM

Manderal bent is the only way to go, If it's less than say 450 hp 2.5 will be fine. over that I prefer 3 inch

COYBILT · #6 10-08-2007, 07:12 AM

Depends on how pumped the motor is. If stock I would go with 2.5 inch or even a mild motor. If the thing has a large duration cam, good set of heads and header go with 3 inch.

SteveMcqueenRules · #7 10-13-2007, 05:31 PM

check out the latest issue of car craft there is a great article on this very topic with dyno testing proof.

6D9 · #8 10-19-2007, 11:09 AM

Car Craft just did an article on 2.5" vs 3.0" exhaust this month. The motor was a 500HP 383 Chevy. Both systems were Flowmaster mandrel bent with Super 44 muffs. Peak for peak there was only a 3HP difference between the two systems. But in the mid range there was a 10hp/10tq gain at a few rpm points. So it at that power level if you have a really low car or dont want a bunch of noise the 2.5" mandrel system with high flow muffs can work really well.

Dang...you must of typed that right before me!

HILROD · #9 10-19-2007, 06:06 PM

My Camaro has a 3in X pipe into 2.5 mufflers and tailpipes. This is with a supercharged 355. I've had fitment problems in the past, worse when mini-tubbed, with 3 inch tailpipes. I did a lot of searching before I bought anything. I think this is the best compromise. I don't think it gives up any noticible power. It's also quieter than full 3 inch systems. When I'm in boost that's a good thing.

Bad94 · #10 10-19-2007, 06:45 PM

I would do 3"

Quote:

Originally Posted by 70gotboost

I was "told"... more than 383 ci, go with 3". Or ANYTHING supercharged/turbocharged needs 3".

LOL, we have 3.5" on a turbo V6. from turbo to rear bumper