What size exhaust system is recomended for a '67 vert with a 450 HP/470lbs tq. 454? Most of my driving is stop and go in Chicago 2000-4000rpm. I am a lead foot where ever I go. Heard 2-1/2" is best for lower rpm power & 3" for higher rpm power? Help...

I would have to say with those power numbers you would want the 3 inch. I forget the guidelines offhand but it was 2 1/4 supports up to 300 H.P. 2 1/2 up to 400 H.P.? Your over that mark so that's why I say 3 in. I'm sure your hear from others with more info/experience. Tim.

3" exhaust would be my choice.

Thanks, I was wondering if there was a chart for displacement and HP/torq. to show the points of change for pipe size?

I think 3 inch is to large, will not create enough back presure, my understanding anything over 500 net requires 3 inch.

Thank's Nick, nice collection!!!

i'm guessing i'm in the 450 to 475hp range and i have 3" to mufflers and 2.5 " tailpipes for backpressure.

Back pressure? What's that?

check out this thread:
http://www.chevelles.com/forums/showthread.php?t=121031

i followed the vote and went 3" but havn't fired it up yet to give you any feedback.

if you are making 450 HP back pressure isn't a consideration. otherwise open headers would be weak. most exhaust manufacturers indicate 3" for over 400 horse.