bluezq8

iTrader: (6)

I am starting to research an LS swap and trying to gather as much info as possible before I get into anything. My question is what size exhaust will work if I am planning for around 400HP? The swap will be with my S10, and the reason I am asking is that I have a Flowmaster cat-back that I plan to install soon and it needs to be modified because my truck is low. The pipes measure 2.5"OD. Should I go ahead and spend the money to get it modified and keep it for the swap? Or should I sell it and go with something bigger?

BTW, great site! I've been lurking for a while and finally joined.

z-maro

iTrader: (18)

I personally think 2.5" is a little small, stock F-body exhaust is 2.75" so I wouldn't think you would want to go smaller than that... just my .02

bww3588

iTrader: (49)

2.5 will be fine. Esp if ground clearance comes into play. The only part of a stock f body exhaust that is anywhere near 2.75 is The I pipe. The outlet of the manifolds and outlet of the muffler is 2.25 or less.

bluezq8

iTrader: (6)

The reason for the modification is to raise the part that goes over the axle so the two don't contact each other if I hit a large bump, so 3" will fit.
From what I have read is that for a street driven car, its better to err on the small side, I assume to retain low end torque rather than power at a high RPM.