Exhaust pipe diameter

[5.0_GT_kid]

I'm wondering about what size pipes I should go with when I buy my GT. I know I'm going to run LT headers and an H-pipe with a Magnaflow catback.

I know most people with Mustangs use 2.5 inch tubing. Cool, but how much will that handle in terms of quarter mile and HP numbers? Should I start out with 3 inch tubing?

Also I was on the Magnaflow site and found their catback exhaust system, but it is only listed as 2.5 diameter. Do they have a 3inch system that just isn't listed?

 

[Badlilstang]

Give us your engine specs and we can tell you wich exhuast to run... if you have a 331 or larger motor id go with the 3" exhuast or if you have a high rpm 306 you may want to go with 3". Im running 2.5" on my 331 and making 373 rwhp. I had the exhaust befor I went with this motor.. id go 3" for my setup if I had to do it over but it worked great with my mid 12 sec 302 I was running.

 

[331 cobra]

2.5 will be plenty for up to about 400hp. Beyond that 3" might be a little bit better but 2.5 would still work fine.

You need to think about what you want to do with your car, and what is realistic.

When I was 17, I wanted superchargers and n2o, but I never had the money for that stuff. Figure out what you want, and what you can get in a realistic time frame. Don't forget about school, it will take a lot of your time.

Now that you have a realistic idea of what you can get for your car, figure out what will give you the most bang for the buck. A mustang with a 3" exhaust and a billet distributor is going to be just as fast as stock. You could get an offroad h-pipe and underdrive pulleys for about the same price, but you will have added power.

Look at the standard bolt on's and try to reproduce a combination that is making good power.

 

[5.0_GT_kid]

Well I'm going to be picking up a 1994 or 1995 GT within the next couple weeks as I've narrowed my search down. I want to do a 347 stroker from D.S.S (just the kit) and top it off with a Edelbrock performer RPM II or Victor intake and AFR heads. I'll stay naturally aspirated by the way.

Of course it'll take time for me to get the money together for the engine combo, I'm just curious how much the 2.5 inch system will take.

 

[Badlilstang]

Well I'm going to be picking up a 1994 or 1995 GT within the next couple weeks as I've narrowed my search down. I want to do a 347 stroker from D.S.S (just the kit) and top it off with a Edelbrock performer RPM II or Victor intake and AFR heads. I'll stay naturally aspirated by the way.

Of course it'll take time for me to get the money together for the engine combo, I'm just curious how much the 2.5 inch system will take.

3" exhaust would compliment that well.

 

[5.0_GT_kid]

Sounds good. Badlilstang I see you run a 331, would you suggest the RPM II or the Victor intake (EFI versions) on a 347? I know mac makes a 3 inch prochamber but does magnaflow make a 3 inch catback for our cars?

 

[85GTlover]

I have heard of guys losing alot of gas mileage and little performance gain. But like others said it would depend on your motor. The sizes are likely common for a reason.

 

[Badlilstang]

Sounds good. Badlilstang I see you run a 331, would you suggest the RPM II or the Victor intake (EFI versions) on a 347? I know mac makes a 3 inch prochamber but does magnaflow make a 3 inch catback for our cars?

Id go with the RPM II between those two. The victor would be good if you were gonna spin the motor high or use forced induction. Not sure on the magnaflow exhuast for 3" I never looked. I know mac has a 3" catback for our cars.

 

[viperos]

well, 2.5" works really well to about 275RWHP... then you want to be running 2.75" tubing... until about 350RWHP, then 3" tubing... if you start w/ something that high, your stang will be worse than a stock 80s neon!

 

[95/5.0stang]

I just got my full exhaust done and its all 2.5 and runs awesome
i can tell a difference between stock

 

[Rootus]

It's worth mentioning that there are people [in this forum] running stock 2.25" cat-backs with 300 rwhp setups. By the time the exhaust gets past the H-pipe, it is much cooler than when it leaves the engine, and it has condensed considerably. If you want bigger tubes, spend the money where it matters to have bigger tubes, which is close to the engine. The cat-back is just for noise.

Dave

 

[viperos]

BUT NOISE MATTERS TO US!!!

-seriously though, I put 2.5" O/R H on, and just ran it like that, dude, I wish I could run it that way 24/7/365.249 (yes, I'm a nerd )

 

[Rootus]

BUT NOISE MATTERS TO US!!!

I know . I didn't say don't do a cat-back, just don't waste time with 3" pipes.

Dave

 

[5.0_GT_kid]

Thanks for the replies guys, I really appreciate the info. Would you recommend the Magnaflow catback?

 

[viperos]

nope... overpriced piece of good quality it really doesn't matter... even the cheap A$$ aluminumized steel will be just fine for you... if you do get steel, make sure it's 16 gague or thicker.... the Jegs Mustang products work really well... full catback w/ mufflers for like $170

 

[Badlilstang]

Thanks for the replies guys, I really appreciate the info. Would you recommend the Magnaflow catback?

I love my magnaflow setup... didnt care to much for the 3.5" pipes out the back but the sound was great and unique. If you want it loud then magnaflow isnt the way to go unless your going to dump it.

 

[viperos]

personally, I was thinking of going w/ some 3" tips... but I would have to order some ones online, the weld ons, are 14" long, and about $60 a pop! so I went w/ some of the screw/weld ons at NAPA that ate 2.75" in diameter... to which I come to find out my stock TIPS are only 2.25" and my H Pipe is only 2"!!! WTF! anyway, just thought you'd be interested to know... the 2.75"ers look awesome!