Just picked up a clean 1994 F-350 with a 460, and it's got a set of Doug Thorley long tube headers on it. They dump into a nice looking Y-pipe, which results in a single 2.5" system the rest of the way out. The truck doesn't seem to have the punch of several other 460's I've owned over the years, and about the only obvious difference between them is the exhaust system, because the others have all been true 2-1/4" duals with no cat (I live in an area where emmissions are not a concern). I'm debating cutting this system out and going with the usual, but it's a nice clean install and sounds good so I'm a little hesitant. But I'd like some input on proper exhuast size for this motor? Thanks!

I would say you need to jump that single exhaust up to at least 3 inch. Also, its speed density, so you could do a mass air conversion. This would allow you to do all kinds of mods and the computer will compensate for it, where as with speed density you aren't getting all the power you could be.

do 4 2"s by running a Y out of each header

I would say you need to jump that single exhaust up to at least 3 inch. Also, its speed density, so you could do a mass air conversion. This would allow you to do all kinds of mods and the computer will compensate for it, where as with speed density you aren't getting all the power you could be.I have a 96 7.5L and I WANT to do the MA conversion but where do you find the parts and all the answers. If anyone has the MA stuff available PM me or call 517 404 2857

I would do at least a single 3"... if not, dual 2.5s. Big blocks like to breathe. Our work truck is a 90 F250 7.5L. Single 3" still sounds like its held back. But, the single 3" helped a lot on power. i beleive the factory after the muffler was dual 2". Id do AT LEAST a 1/2" on each pipe over factory.

Ive seen 4" too, but never rode or heard about it. But, people are doing it. ive seen 390s run dual 3" and be okay... Barely even tuned, but they were carbed.

Not to disagree with the great minds of the PBB... Well ok a lone voice in the wilderness. One of the key needs of an efficient exhaust is velocity and as the gases cool velocity drops off. Keep reducing the tube diameter as it moves away from the source and it should retain velocity to the end.

This is where the engineers poke fun at me.

i run dual 3" into a single 4" to single 3.5''' works VERY well....but this is a fairly built 460.....

i would think 3" would be ideal for your setup....2.5" probably works fine because i know how the efi 460's dont have all that much oomph after 4k

X2