this might be a dumb question, but its bugging the hell out of me. everyone says a 3" dia. single exhaust is perfect for a mild to moderate 350 in one of our cars. if thats the case, why can I not find a damn y-pipe that has a 3" output? they all seem to be 2 1/2". why go through all the trouble of a 3" exhaust and nice headers to strangle it all down to 2.5" right after the headers?am i missing something here? there's all sorts of advice on which pipes are easiest to cut and splice a 3" outlet into... i just have an issue buying something for around 200 just to hack a third off and splice another new piece on. seems like a waste to me

basically, does anyone just sell a 3"output good flowing y pipe anywhere that doesn't suck? i just want to buy a nice set of headers, good y pipe minus the 2.5" bottleneck and go with it.

thanks

Thunder

I agree, there isn't a single model out there that has a 3 inch outlet besides the famous hooker 2055 combo. And hooker won't sell the y pipe seperately, so youhave to pay nearly 500 for the headers and y pipe. I am just gonna buy the hedman set and use the trusty chopsaw and cut the portion of 2.5 off at the y and weld in 3 so that it's the correct length and proper sizing.


Cheers!!!!!

500? the hooker 2055 setup on summit racing is 800... way more than i am spending.

the scenario thing in your signature is great btw

the heddman is very reasonable.. thats a cheap enough ypipe i don't think i would feel bad cutting it up. thanks for the suggestion

You must be looking at the coated Hookers. Uncoated are $450 or so.

JamesC

Another possibility to consider (especially if you're willing to modify the cat): www.summitracing.com, HED-68491, $365.95. These are the dual-cat version, have 2-1/2" pipes to each cat. Put a "Y" after them, attach to 3" cat-back. Or, dual cats, "Y" to cat-back (like stock dual cats).

A 2.5" y-pipe is NOT a restriction. 2 2.5" pipes will out flow 1 3" pipe all day. You gotta merge at some point. If you are merging 2 3's into 1 3 then that is a greater restriction than 2 2.5 into 1 3. The fact still remmains that unless you are at 500hp at the crank (or more) the 3 inch system is overkill anyway. But mabe I just understand how to size a system based on performance, over the look what I got or it sounds cool factor.

3" Y-pipe and single 3" system all the way back is good for 400hp tops. I thought it would flow more and I had 375hp at the crank in my Trans Am with a 150 shot of spray on top of that. When I hit the spray with the exhaust hooked up (Hooker 2055's 3" all the way back) It felt like maybe a 50hp gain...I took the Y-pipe off right before I sold the car and hit the spray running open headers and WHAMO it felt like a 150 shot. So 400hp maybe 425 with a single 3" system at most proven! I did this test because other people on this board said 400hp at most...they was right! When building the Camaro I just got I am forsure going with duals.

That's a smart idea, I forgot about dual cat cars. Spectacular I say!!!!

Word of caution - this is butt-dyno info, not quantitative. Having "felt" the surge of power with open headers, then comparing the time slips (same day runs) to the no-surge feeling of capped headers, and seeing that the capped runs were all quicker in 60', 1/8- and 1/4-mile ET, and MPH, I'd take all of your "data" with a few grains of salt.

I should correct myself,sorry---fatfingerd the 5 --meant 400hp in prievious statment.
This according to popular Hotrodding----their numbers not some muffler company.
A 2.75” (stock) single system is good for a 310hp engine with zero loss…
A 3” Single system is good for a 370hp engine with zero loss…
A 3.5” Single system is good for a 503hp engine with zero loss…
A 4” Single system is good for a 657hp engine with zero loss…
A 2.25” dual system is good for a 457hp engine with zero loss…
A 2.5” dual system is good for a 513hp engine with zero loss…
A 3” dual system is good for a 812hp engine with zero loss…
The fact still remains that MOST of those upgrading their system are doing so to a BASICLY STOCK powerplant.....and thus a single 3" system is still overkill even with a 2.5" y-pipe. the system overall probably was not your problem 4play most likely your muffler-----what were you running?

awesome information... what horsepower rating does a 2.5" single top out at?
i don't know what my mods are going to bring my engine up to.. i am just starting out with headers, y-pipe, edelbrock intake, runners, porting the plenum.. upgrading the ignition, wires, plugs, etc. maybe a chip and a cold air intake as well as the standard suspension upgrades (subframe connectors, strut tower bar, wonder bar). i have a stock tpi 350 with a very low mileage acdelco remanufactured engine (previous owners popped it just before i bought it and had it replaced on warranty)

I just wanted to have the full 3 inch pipe so that i can grow into it without having to tear the exhaust completely apart again in the near future.

ps.. if factory is 2.75, why are all the aftermarkets 2.5?

It was butt dyno and I tell you it is real accurate...lol! My butt dyno was calibrated from 4 previous runs with spray full exhaust. Open shorties was way faster on spray. Open shorties no spray was same as full exhaust on the butt dyno...lol!

Real numbers according to the butt dyno though I bet car would be at least 1/2 second faster in the 1/4 mile give or take .0002 or .0003

Seriously though it was night and day difference, full exhaust was holding it back big time on the bottle!

Only LG4/LO3 aftermarket are 2.5". "Most" are 3".

This setup is good for 400+ with a 3" cat back:
PM me for details