Yeah, 2 1/4" at least. If you're starting from scratch go with 2 1/2", leaves you room for further mods. 2" is pretty small, it has only 3.14" of surface area (pii*r*r), where a 2 1/2" pipe has 4.9" of surface area, pretty big difference especially when you have 2 pipes. I doubt that you would lose anything down low, but you would for sure gain up top

 

im going to be doing 2.5 with my longtubes that should be good for low end ?? 2 cats 2 mufflers also H pipe

 

The loss of low end comes from loss of scavenging which comes from loss of exhaust velocity which comes from the exhaust tumbling in pipes that are to large.

 

I know what you're saying, just in this case the major restriction caused by small pipes far outways any "scavenging" benefits they may have, which I don't think the smaller pipes do in this case. Factory exhaust systems kill any scavenging effect there is, manifolds are not designed for this. Case in point, any engine will make the most power with a properly tuned set of full length open headers like last rights has, ie for a 5.2/5.9 - 1 5/8" or 1 3/4" primaries, 3" collectors approx 18" in length. When you add an exhaust system you actually lose most of the scavenging effect because you are lengthing the collector where your scavenging effect comes from. As a matter of fact, to get the most out of your system you make whats called a zero loss exhaust system, which is basically a really oversized exhaust system after you collectors that "fools" the exhaust into thinking they are still expelling into open atmosphere. Where I got all this from is an article by David Vizard. Anyone who reads the popular hotrodding engine masters magazine will recognize the name. Look it up, it's interesting.

 

I have 2 of his books, lol.

 

Hah, small world!

 

i talked with several exhaust shops before i got mine done....they all suggested 2.25'' piping, but i liked my buddies exhaust setup so i did the same and got 2.5'' piping instead. love it

 

how much did that run you

 

Meh, to heck with it, pick up a set of Summit shorty headers for $160 (SUM-G9044 for 94/95 trucks or SUM-G9045 for 96-02) use your stock 2" take downs into a 2 1/4" x-pipe (SUM-643122 $70) then go 2 1/2 after the x-pipe and do a race exit in front of the right rear tire... Most states would agree, that as long as it exits behind the passenger cab, it is legal.

I had my wife`s 96 rcsb 318 5spd routed that way and only got in trouble for it being excessively LOUD. Man I miss that truck, I had evil stroker plans for it; that thing was light! (~4,000#)