Diameter question

SpitfireEMT · #1 07-06-2011, 09:47 AM

I am going to be redoing my exhaust from the heads back in the spring. My plan is to run JBA headers (1 5/8" primaries), down to 2" pipe, high flow cat on each, then into an x-pipe and then run straight back to where they currently dump. My questions is: with ported alabama heads, how small does the pipe need to be to provide adequate back pressure to keep my bottom end torque? is 2" too small or can I run 2 1/2" and still be okay? I already have around 40' of 2 1/2" laying around the shop.
Thoughts??

doyouquaxu · #2 07-06-2011, 09:54 AM

IMO don't waste your money on high flow cats, the ones on your truck flow just as well.

SpitfireEMT · #3 07-06-2011, 09:58 AM

I dont think putting 140k mile cats on a freshly rebuilt engine is a great idea. Maybe thats just me tho.

doyouquaxu · #4 07-06-2011, 10:02 AM

Quote:

Originally Posted by SpitfireEMT

I dont think putting 140k mile cats on a freshly rebuilt engine is a great idea. Maybe thats just me tho.

don't cloud the issue with facts... lol

SpitfireEMT · #5 07-06-2011, 10:28 AM

Depending on what pipe size is needed, I may run straight pipes. The truck will be a strictly off road vehicle next summer, so I dont have to worry about the treehuggers getting snippy at me driving it down the road. I would guess 2~2 1/2 would be sufficient to keep my bottom end. Didnt know if anyone had messed with it or not.