[78w72]

hi. i'm ready to purchase an exhaust system for my 72 firebird & am having trouble deciding which is the best way to go. looking at the pypes kits with dual mufflers but my dilema is do i get the 2.5" or 3"? so i'm looking for some input &/or pics of a 3" system on a early 2nd gen, or later years too. the engine could benefit from 3" & although its not a full time drag car i dont want to choke it out with 2.5". who is running 3" on their bird & what problems did you run into for clearance on the floor? i know the cross member can be an issue or the cross braces in the floor, & possibly the fitment of the tail pipes in the rear. the car is lower than stock but not excessive & the headers do hang a little lower than most due to their tube size.

i looked into doing a custom kit with 3" x pipe & 2.5" tail pipes but pypes doesnt make that easy if you want to order it that way, they make you pay full price via PY & charge shipping on top. yet summit & jegs has super low prices for the standard kits but pypes wont let them order just rear tailpipes. you'd think they would offer the custom kits for guys with higher hp engines or be somewhat competitive on the prices with the larger retailers they sell through, but apparently not. i am all for buying from PY but just cant justify $100 more compared to summit when on a tight budget. so its looking like if i want to have the better flowing exhaust for my car i need to buy the 3" kit, or piece it together to get the 2.5" tails & spend ~ $100 more.

engine dynoed at almost 520 hp with no tuning yet & i have plans for more power in the near future. pretty sure 2.5" will not be enough for this engine. pics & opinions would be a huge help...

400/467
stock e-heads
old faithfull roller cam
SD ported cast iron intake & cliff prepped q-jet
hooker s/c 2" headers
th-400 trans.

[2002Z4CSS]

My son has Hooker 2" primary headers on his Big Block Chevy powered 1979 Camaro with a 3" exhaust system that is bent like the stock exhaust including the tail pipes. Not a lot of room back there by the shocks, leaf springs and shackels and the rear sway bar end links but it fits. 2 1/2" exhaust will have more clearance.

[torqjunki]

I would chose a well designed mandrel bent 2.5" system over a cobbled together combo. For a primary street car, there is nothing to gain but noise, weight, and clearance issues with a 3" system. See my performance sig below. 3" non-mandrel bent pipes from headers to 2.5" flowmaster (don't flow that well) mufflers, and 2.5 mandrel bent tail pipes (flowmaster brand ordered from Summit.) Even the crossflow systems will work to around 500 HP and no mufflers hanging under the car.

[ponjohn]

Interesting combo...e-heads with iron intake.

Cool.

[78w72]

Originally Posted by torqjunki

I would chose a well designed mandrel bent 2.5" system over a cobbled together combo. For a primary street car, there is nothing to gain but noise, weight, and clearance issues with a 3" system. See my performance sig below. 3" non-mandrel bent pipes from headers to 2.5" flowmaster (don't flow that well) mufflers, and 2.5 mandrel bent tail pipes (flowmaster brand ordered from Summit.) Even the crossflow systems will work to around 500 HP and no mufflers hanging under the car.

nothing cobbled together, it's all mandrel bent stainless from pypes. it would basically be their 3" kit but with 2.5" tail pipes. its about a 75% street car, will see track time but mainly for fun & tuning. just figured the 3" x pipe would be worth while & for the price savings just get the whole kit if it fits well. i know there are lots of firebirds out there with 3" full exhaust, hoping for some pics of opinions to help me decide.

[78w72]

Originally Posted by ponjohn

Interesting combo...e-heads with iron intake.

Cool.

yes, not my first choice but i'm going to be running a formula hood & it's the only combo that will fit right. of course i could run a torker or tomahawk type intake but i want to use the q-jet for now since its mostly a street car.

intake was done by SD with their "stage 3" cnc port. opened plenum per cliff's design & then hogged out the runners & matched to the e-heads ports, very nice job on the intake & SD says it has supported up to 600hp on one of their builds. im at about 520 on a brand new engine with no tuning so i would like to do a 3" exhaust if its not too much of a hassle. or a 3' 2.5" hybrid.

[Skip Fix]

Torque Tech 3" tailpipes fit great plenty of room. Downside they exit below bumper do not "correct" for a 78.
I'll see if I have pics at home.

[ta man]

You can always order 3 inch Pypes X crossover ,use cone reducers into good flowing 2.5 mufflers (I use Ultraflows)and order 2.5 flowmaster tailpipes...
I've ran almost 119mph with a similar setup..the smaller tailpipes help mellow out the exhaust note too.

[78w72]

skip: i dont like under the bumper pipes, correct or not, just dont really like the sound. i plan to have the pipes exit where the dual splitters do on a later t/a. pypes said you just cut the pipe after the hanger & re weld a straight piece angled to where you want it.

t/aman: thats kind of what im considering doing however the cone reducer isnt stainless like the rest of the system. i am planning on using the pypes race pro instead of the ultraflo's, the race pro's case is the same size for 2.5 & 3", they are 4" tall, the ultraflo's are 4.5" tall. so i save a little money with race pros & a little space. & at 3" they should flow just as good as the ultra's. then its just a matter of expanding the end of the 2.5" tails to fit inside the 3" muffler.

[MG12692]

I have a 72' bird with dougs headers 1 7/8 primary. 3" pypes systems with 3" super 44 flowmaster mufflers ( 4"thick casing instead of 5" casing provides a little more ground clearance) I did the install in my garage with the jegs brand band clamps. Also have the dougs electric cut outs just to be fun or obnoxious. : ) Did not have any major issues.

[grandville455]

3.5 Pypes X with 3" Ultra flos and 3" Torque tech tails..

[Skip Fix]

The only way for a 3" at splitter location would be to cut and section (which I have plans to do) where it comes out at that last hanger kind of like the Pypes adapters for splitters on their 2.5". Also most commercial splitters for 3" are a 2/5 bumped to slide on a 3". A 3" SS 45 could be cut to make a real 3" splitter. Problem there is it gets real tight through there and the leaf spring to body area.

[78w72]

nice pics of the 3.5" x & 3" tails. looks like the x & mufflers fit "ok" but the t/t tails might be a problem if you run a sway bar which i intend to do, & they need center outlet mufflers, pypes mufflers for their kit are offset/offset. so i think the sway bar kills the t/t tails. but thanks for the pics.

mg12692: good to hear you installed that kit ok, can you post any pics?

skip: sounds like what pypes told me to do, they said just cut the tail after the last hanger, then reweld or clamp a straight piece to exit between the leafs & quarter panel. no adapter or sectioning was mentioned. & to be clear, i dont want the splitters, just a single fat pipe exiting in that location like in darby's pic.

if 3" pypes tailpipes will fit there i will just make it easy & buy the 3" kit, but 2.5" tails would be easier to do & probably a little quieter.

[Skip Fix]

Here are side shots of the Torque Tech and a rear one. Fine with a sway bar.

[78w72]

looks good. are your mufflers center or offset outlet for the torque tech tails?

[jonmachota78]

All 3"
Pic 1:Was like this for years never liked it..
Pic 2: hackd it off even and put some bends on i picked up from the pypes tent. Kinda cheezy but the kids liked it.
Pic 3: chop saw the bends... more subtle i guess. Kids liked em shooting out the side. It did sound quieter.
Pic4: ended up going this route

[jonmachota78]

Originally Posted by grandville455

3.5 Pypes X with 3" Ultra flos and 3" Torque tech tails..

Looks good, Darby. eventually I'll probly just cuttem off like you did... it's just hard to uncut it later so I've been dragging my feet

[78w72]

uh, pic #4?

what i want to do with the tails whether i go 2.5" or 3", is to cut right after the rear most hanger then agling it to come down right where yours are in pic 3 but with a straight piece of pipe. so it will angle down just like the dual splitter tips for 78's. basicallly just like in darby's last pic. hopefully 3" pypes tails will let me do that.

[Skip Fix]

I have offset inlets/center outlets. That is how my original 2.5 system was and the electric fuel pump is next to the frame rail where offset/offset would not work unless I moved it. I had to add about 3" between the two Torque TEch pieces to do it as they are set up for offset/offset. I have Dynomas Ultraflows on it now. Dr GasX 3" in front of them.

I really played with the 3" tailpipes under the Camaro when I had the tank and everything out and I really think at least on Torque Techs there is enough room between the spring and the body for a splitter to kick out.

[Blued and Painted]

Almost 4 inches of ground clearance with 2 1/2 dynomax and some saggy rear springs.