Roadking67

Hey everyone... New guy here and was wondering what exhaust set up you guys are running. I currently have flowmaster 40 series with each side going straight in to the muffler (no h pipe or cross over) in 3 inch diameter. I was planning on doing 2.5 from header to tail with an h pipe. I really don't know why the exhaust shop went 3inch as I don't particularly feel I need that big of pipes. Motor is NA, mild cam (cannot recall) aluminum ford racing heads. Very mild mods I would say.

jlg2002

you don't say if it's a Windsor or FE eng. Do you have headers, 3" pipe is kind of big on a SB car IMO - 2-2.5 inch with cross over pipe recommended.

BuckeyeDemon

why change it if it's already done? do you not like the sound? was it not put together well?

most people seem to stay away from 3" on early mustangs simply because of the difficulty in routing.

Roadking67

It is a windsor engine. I don't mind the sound but I wanted to do the piping to the rear of the car as it currently has dumps right after the mufflers. Also adding the H pipe would help create a better flow and better performance correct? that is why I was thinking of changing at the time of adding the h pipe and bringing the pipes back. Yes it does have headers, long tube.

BuckeyeDemon

you could have them add an H-pipe to your existing setup along with routing a reduced size set of tailpipes to the rear. it may save some money. you would have to check with the shop that does the work.

tx65coupe

That 3 inch pipe probably wont scavenge as well. I'd run 2.25-2.5 inch pipe with an H pipe. I'd also loose the dronemaster mufflers and run full tailpipesnot dumps. I have Dynomax Ultraflo on mine. It sounds perfect. No more chambered mufflers for me.

2+2GT

I agree, I'd use 2.25" unless the car is actually used for racing. Heck, the 67 GT 500 428 2-4V engine used 2" exhaust. The 2.25" didn't appear until the 68 428CJ.

BuckeyeDemon

scavenging isn't an issue much after the collector. think of a siphon blaster media blaster or siphon paint gun. the suction can occur where the flow is running across a low pressure area. after the collector this situation doesn't occur anymore and it's just backpressure.

that's my opinion.

Roadking67

after header collector or after the crossover? I am assuming after the crossover right?

BuckeyeDemon

i would expect mostly at the collector. the h pipe basically provides two paths for the exhaust to go.

i would have a hard time believing the scavenging (or siphoning) signal produced at where an h-pipe or x pipe is located would have much of any impact on cylinder filling (i.e. when the exhaust valve and intake valve are both open and the suction helps pull on the intake charge instead of pushing back on the intake charge.

again, just my unexperienced opinion.