moparman1975

Yes, I know everyone is going to vote 2.5" but here's the details.

My 84 GT is going to have a stock 88 5.0, shorty headers, H-pipe, and a flowmaster cat-back.

I found a 2.25" FM cat-back with stainless tips and 40 series muffs for under $190, the same setup in 2.5" jacks the price up to $300-$320. Will the sound be similar to the 2.5"? The 2.25" should be more than enough for a stock to mild 5.0. Right? If I spend the extra $100 will I see a noticable difference besides a lighter wallet?

PRO50SC

Yes, if you're not going wild for power it will be fine.

95ConvGT

Well it depends if you stick with what you have then a 2.25 will be fine but if you plan on going forced induction then you need to step up to a larger one.

stanglx2002

the 2.25 pipes was a way for ford to restrict the cars some more. the 2.5 pipes are used to increase exhaust flow to gain more hp

ZachW04Stang

Summit racing has flowmaster american thunder exhaust for $240. I think it would be worth spend $50 more instead of getting a cheap cat back. Just remember you get what you pay for.

Tims 88GT

2.25 restricted? no way I mean come on people back in the 60's Mustangs, falcons, Galaxies. so on but they only used 2 inch exhaust and still made major hp, some cars were only single 2 inch and made 425 hp. you will never notice the difference in performance from 2.25 and 2.5

stanglx2002

bs you need to do some more research and learn some more. take one of your 60's mustangs making 400 hp and put a 2 inch exhaust to a dyno and then take the same car and put a 2.5 in exhaust on it and see if it doesnt make more power. Im sry but you are wrong I had a 2.25 inch exhaust with cats my 331 and then put my 2.5 inch exhaust when it came in the mail and i gained about 20-30 hp

SAKONNA

Bigger isnt always better, man that sounded korny. but anyway, the 2.25 system will sound a bit better than the 2.50 system. the smaller the pipes, the snappier the sound. If he isnt looking to exceed 300hp the 2.25 is fine and you'll gain a little torque. Plus, you'll get out of that annoying buzzing coming from under the car because the exhaust is hitting the frame lol. Ultimately, it's up to you. the 2.25 system with a O/R pipe and flows sounds good!!! Just make sure your entire system is 2.25....if you're off road pipe is 2.50 and you want to add a 2.25 system, you're creating a bottle neck....and that's just Dumb lol 2.25 off road are so hard to find these days....everything is 2.50. Now, I am not knocking the 2.50 system, cause that wayy good too, but it's just my 2cents

nitrous_bob

if you at least get better the headers, the 2 1/4" won't be so bad. the headers are the big restriction w/ all the pinch points.

but i do think it will run better on the 2 1/2" w/ stock motor even.

my old notch went 13.60's on 4.10's w/ et streets (bone stock), the next spring by doing just the exhaust , it went 13.20's. i used long tube mac's , flowmaster american thunder 2 1/2" catback.

now, thats not saying i didn't improve my driving style some...but that was a big difference imo.