i was curious to know if my exhaust pipes are too large for my setup, too small, or just right. I have a 350 sbc bored to a 355, ported dart ie pro 180 heads, comp cams XR276HR-12 hydrolic roller camshaft, hsr, 24lb injectors, 58mm tb (i wanted a 52mm but i got that one for free so i won't complain), 3000 stall converter, 3.73 gears, hedman lt headers connecting to 2 1/2 inch piping into a 3" y-pipe that connects to a 3" catback (flowmaster 80 series) exhaust i have in the back, and 9.6 cr. do you think 2 1/2 is too big, too small, or just about right for my setup? i plan on supercharging her in about a year or so, so im sure when that happens i'll have to get bigger pipes. thanks for the help guys

 

you have me confused on one thing...2 1/2" pipe from header to a 3" Y-pipe? your headers don't connect right into your y-pipe? i am slowly starting to picture what you mean, so by the time you answer i will get the whole picture, lol. i read an article from Flowmaster a while back and they say 2.5" pipe is sufficient up to 350 hp. above that you need 3" for added flow. if you have too big of pipe you will not flow more, you will actually hurt by not having sufficient backpressure and it will have turbulence in the pipe and not flow. in short, 2.5" should be sufficient for your application. you DO have the 3" backpipe, but seeing as it is a single exhaust, you should still be ok.

Josh

 

hmm... since im at work i can't really do a nice photoshop drawing... so you're stuck with my mspaint skillz lol

 

http://www.flowmastermufflers.com/cg...r/muffsys.html

 

i would say that is a bit small of an exhaust...for one that flowmaser muffler doesn't flow really that good...then that 2.5" y pipe is your bottle neck there....i got the same cam, almost same motor as you have....and i'm running dual 2.5's and I think that is just right...and that flows way better than any flowmaster catback system...i think you got a restrictive exhaust on your hands...

 

I think that the only part of your exhaust that may be restricting is the Flowmaster catback. dual 2 1/2" pipes outflow a single 3" pipe. I don't think its that restrictive tho. For peace of mind, there are plenty of LT1 4th gens running a Mandrel bent 3" catback with well over 450hp.

 

yea my buddy is running 12.5 with his 2000 z28 with stock i pipe and y pipe, aftermarket headers, and 80 series replacement muffler...now he has a hooker catback, stock y pipe, and headers, running 385 rwhp, plus he just added a 150 shot of nitrous....you can get a catback to flow real good, just use your head...he noticed a big difference over switching to the hooker catback...

 

Thats correct indeed. A large advantage that the aftermarket cat backs have are the mandrel bent tubing over the stock "kink" bends. The hooker muffler flows much better than the flowmaster, and sounds alot better as well. I just ditched the borla for my car, in favor of true duals. I don't really have enough power to warrant the 3" pipes yet( only 340RWHP) but I am sure I will soon.

To the threadstarter, if you feel you think the flowcrapper is holding you back....look into replacing just the muffler. If you don't mind a single outlet, look into Dyno-Max Ultra-Flo welded mufflers...They flow great, and IMO have a sweeeeet sound.

Kyle

 

Well i have a lot of things i need to do before i can change my exhaust system... gotta get the car running now (blew another intake gasket), tranny fixed, the car tuned, and then a paint job. then i'll worry about the exhaust... i'll probably go with a hooker catback too, i've been eyeing that for a while

 

I think it's a good all-around system, maybe just change the muffler as long as everything else is mandrel-bent. In the future, I might consider the dual 2.5" into 3.25" or 3.5" y-pipe, and then go with that size all the way back.