I have a 93 F250 4x4 351w.I'm installing pace setters 70-2221. No cat. My question is about pipe size, do not have access to mandrel bend at any shops in the area. would installing 2.5 in to muffler cost me anything or should I just go with 3" all the way back? 3" Y then into 3" muffler & tail pipe. The vehicle is used to pull camper trailer. This is the start of a build with 444232 cam, GT40s, and 1.7 rockers. I think I'm on the right track. Thanks for any info. JMDMT

 

Your asking us to guess what you need. To do a build that will maximize performance all components need to be engineered to match. you can over exhaust & you can under exhaust. My suggestion is build your engine then worry about exhaust.
The people to ask are the guys that build custom exhaust systems. What does Pacesetter say? They have the engineers.
Craig

 

Are you going to run dual exhaust? I've had good luck running both 2.5" and 3" exhaust on 351w's as far as duals go. If you run duals into a single, you could run 2.5" into a 3" outlet muffler or something of the sort.

 

The muffler shop is gonna have enough trouble wraping 2.5" tubing around the frame crossmembers and T case so my suggestion is 2.5" from the headers back to a 2.5" to single 3" pipe down the passenger side and then either a dual outlet muffler if that's the look you like or a 3" single tailpipe. Be aware that without a cat this system will be loud and drone in the cab at highway speeds.. especially after you get heads and a cam on the motor and I would not under any circumstances recommend any Flowmaster(Dronemaster/BLATmaster) muffler.