2.25 or 2.5 inch exhaust.

[blown65]

Well seems how they cruise down the road at a constant 8Krpm’s and most of us here don’t, I think your analogy is poor at best.

after owning many V8’s over the years and few small blocks, I would say that pipe diameter is more a matter of what the car is being used for and less about displacement. Most street cars make their usable power at lower rpm’s and smaller pipes aren’t a performance issue. I realize this is a stupid blanket statement (it should be right at home inside this thread), but in general small pipes hurt a race engine and big pipes hurt a street engine. Personally, I like bigger pipes for their acoustical purposes.

I was replying to him talking about 3" on mine being too big. (not directly but its what he was getting at)

My car sees 8500+ at the strip and shifts are at 8100-8300. Still think I should run 2 1/2"? He thinks no 347 should need 3".

I had 2 1/2" on my car for a while, it sounded like total horse crap. The velocity coming out of the pipes at 8000+rpm was hideous. Its the same deal with my blower motor, sounded like total crap at 2 1/2".

 

[tx65coupe]

I run 2.5 inch on my warmed over 302. I think it would have worked almost as well with 2.25 inch.

I was saying that if someone has a stock 289 with a 2 barrel they do not need to upgrade the exhaust to 2.5 inch.

I agree that 3 inch exhaust may be required on a really hot engine. Not all 347s make 600 hp though.