Jim85IROC

iTrader: (6)

I'm doing an LS swap in my IROC. 402, LS3 heads, blah blah blah. I expect to be in the range of 500-520 RWHP. I currently have a 3" single over-axle exhaust going through a 3" muffler with a single driver side tail pipe. I'd planned on going to a bigger exhaust when I do the LS swap, but if what I have won't be a restriction, then I'd rather just keep what I've got.

Opinions?

Jim85IROC

iTrader: (6)

Oh crap. I just realized i posted this in "internal" engine instead of "external".

Sorry.

cam

iTrader: (9)

IIRC you need roughly 2.2 cfm of exhaust flow per hp to flow unrestricted. That said its not like 3" will rob 50hp away on a 500whp build vs a single 4". The difference would be noticeable but not huge. The sticky in the external engine section has some great info but sadly a LOT of the great pics and charts that jrp originally posted are now gonzo or dead links. Heres a pretty good guesstimate for a quick read

https://ls1tech.com/forums/2987587-post19.html

garygnu

500 hp is the limit for a 3" system,and I feel you will be making close to 550 rwhp .you could splice a flowmaster 3<4 merge pipe into your Y-pipe and use 4" cat back.

sjsingle1

iTrader: (1)

get a 4" cat back anyway !!!!!