I finally got around to get my tranny rebuilt and now my car runs good so i have order the dynomax cat-back system and getting a custom made y pipe for it and I will knock out all the baffles in the cat and make a test tube cat. Can anyone give me a guess on how much hp i will gain.

all the pipes will be 2 1/2 inches.

I'm guessing between 10-15 HP. I put a dynomax exhaust on my car and i felt the difference in mid range RPMs. It really made a difference with my car. I felt it as soon as i took it out for a drive around the block plus it sounds a lot better too.

honestly....i wouldn't go 2.5" on a v6 unless you're pushin a ton of hp out of it (like 350hp or more). i have a built (big) 3.1 and am running dual 2.25" off of the headers into a single 3"

You'll gain at most 5 HP ( I doubt even that) 2 1/2" pipes to the rear is perfect and only use a single (not duels) 3" pipe is too large and will slow down the exhaust gases to much and cause premature cooling- thus robbing power. The cat gutted will only show power above the 4000rpm range unless it is very old and blocked flow from burning oil.

when i did mine i had a huge diffrence but i also has a custom y pipe and some extra stuff done as well, but since i got it am able to burn my tires off the line. and before i had to almost put the gas to the floor to do a burn out on dry land not not even 25% down and it burns like he11.

In your case it help because with the custom y-pipe installed will give better flow above 4000rpm's then the stock headpipe (T-pipe ). With that freed up then the cat can be freed up also and you'll gain signifficant power above 4000 rpm's. Otherwise gutting the cat alone (or going to a high flow cat) is pointless.

I'd guess 5-8 hp..... My catback and high flow cat made a significant difference. My 1/4 mile, G-Tech, was at 16.48 after those mods. These were my only mods worth mentioning..and the car should've run in the 17's stock seeing as it's an auto.

when I said custom y pipe I meant the pipe that runs to the single cat what you guys call the t pipe. He said he would make some headers for it but it would cost me about 450 for both to be custom made. and I am wonder how big is the opening for the 2.8 cat in and out?

cat is 2 1/4" in and out, i took my cat off when i had my 89 camaro, i didnt notice a change at all, once u get to 4000rpms your outta the power band thats 3000-3500 rpms, i say leave the cat alone, it wont change enough to make it worth your effort. i was reading in jeg's a few minutes ago, they got a flowmaster muffler advertized that is a 10-15hp gain...how??? if a cat back only gives u 5-8 how does just a muffler give u 10-15?

that 10-15 hp that muffler manufacturers advertise is typically the biggest improvement that was found, probably on a HUGE motor switching from a stock type (very restrictive) muffler to a flowmaster that can handle the exhaust that is pushed through it.

AGood2.8, i said i am running 2.25" duals off of the HEADERS into a single 3" catback....this is big exhaust for a stock motor but i said i have a big built 3.1. trust me...this motor needs that exhaust to breathe... on a stock or nearly stock motor you might go 2" duals then see if you can find something between 2.5" and 3" for the single pipe.

Who's headers are you running? What have you done to your "built" motor to justify running a 3" catback? I promise you from experience that you are losing HP with that size catback- You'll have better performance out of a 2 1/2" I-pipe on a little 185ci motor with an exhaust system as long as F-bodies have.

AGood2.8 - I am running hooker super comp headers (been around for a while)and they have 2.25" collecters. my built motor...its a 3.1 (191 ci) bored +.030", 10.75:1 compression ratio (yes it runs fine on pump gas), completely ported and polished heads and intake manifold, largest valves that gm produced for these motors, crane cam (.484" int. lift and .512 ex. lift and a lot of duration), 1.6:1 roller rockers, plus cold air intake then the exhaust. have you ever built a motor like this???? idling...this little v6 sounds like a nice v8. i'm sorry you feel that i am killing my hp with the 3" i-pipe but i ran the stock "catback" for a while, until i got the 3" and i wil absolutely not go back to it! the 3" sounds better and performs better. i don't know if you even drag race your car but if so, have you ever seen 9s in the 1/8th (not including any nitrous)? if the 3" hurt my car...why did i pick up over a tenth and two mph right after i put it on??? any other questions or comments????

1)Yes I know Hooker headers- I have three sets of headers for a V6 Camaro 3rd gen- one being Hooker Comps. I'd really like to see a picture of your y-pipe setup?

2) I'm currently building a 3.4 with 1.8"intake, 1.42" exhaust heads (stock being 1.72"intake) You must not have seen some of my previous postings.

3) You are the first person I have seen on these boards to claim to have modified your motor extensively- How about some pictures or track #'s, I 'd like some more proof to your claims, I am still in experimental stages with this little motor and am always looking for more factual info.

4)Do I drag race? Have I seen 9's in the 1/8? (I know your are taking about your V6 but-) I have a 10sec 1/4 mile roadrace Vette. Yes I know how to build a motor (and a complete car for that matter) My 2.8 in the car right now has turned a 15.8 1/4.

Lets see proof- If you are for real then I'd like to talk in person- I like to know for certain your not just another 16yr old kid that can type B.S. Lets see some proof first.

here's two of my timeslips. this is on a stock tranny and rearend and some pathetic 235/60/15s. i can get you some pics of my y-pipe but the one that is on the car now is flex pipe and kind sad but i'm going to get a real one made for it. yes, i was refering to what this bored is about...v6 third generation camaros and birds. no, i'm not a 16 year old running my mouth....i don't like those kinds of people, i am 18 and will only tell you facts...i do not go around making stuff up to make myself look good.

I am 1915

here's some pictures of the exhaust that's on there now. like i said, i'm going to get it redone that was only put on to connect the headers to the exhaust so i could drive the car.

here's a couple of pictures of my car (and my friend's mustang in the background).

Hey man! You in central Florida? Where abouts? I run at G'Ville Raceway every once and awhile.... Livin' in Ocala!

i live in tampa....i run at lakeland when i run. it's only an 1/8th mile unfortunately. i want to go down to brandenton to run desoto...1/4 mile!!

O.k.- things make more sense now that I've seen your pics.

1) you are not running a catalytic conv.
2) Ground clearance is not an issue for you, So you can run directly towards the rear extending the length of your Y-pipe primaries untill they dump together near your back seats, then into the shorter 3 inch pipes (unlike the long routing of the stock location exhaust and restiction slowdown of the cat.)

You basically have a shorter faster excavation of exhaust gases and can get away with the 3" without substantial cooling from the length.

I don't have that liberty for two reasons:
1) I live in the **** state of Calif.
2) I have major ground clerance issues and have to maintain the stock routing location of the y-pipe and catback- I was vigorously checking into going 3" cat to catback and dumping out the side of the car (to shorten the exhaust flow) but just no room possible to do this with cat and a muffler underneath the passenger seat area.

Sorry to jump into the post with nothing useful to say, but--more Central FL people! Hell yeah! AM, you ever run at Bithlo (Orlando Speedworld)? The track kinda blows, but it's the closest to me.....maybe 50 odd miles each way.

You want real Hooker headers /2" primaries & 4" dumps/ only 2" primary headers that Hooker ever made for a smallblock-{ 327ci 540rwhp, 8500rpm's}. If only I could run sidepipes legally on a Camaro (this wouldn't fly pulling into a smog station here in Calif.) Besides Sidepipes would look like crap on a 3rd gen.

If only I had the photo.... My friend has a 84 T/A with black glasspack sidepipes. It's.....interesting looking. His sidepipes are CHEAP though....spraypainted so half of it's coming off, and they're attached via Bungee cord with the two metal ends welded, one to the pipe and one on the frame somewhere. Ankle burners those damn things are. Can't recall how many times I opened his door and slid out and either cursed for 5 minutes straight or thanked *** that I had thick socks on.

actually ground clearance is an issue, that's one reason that i have to get a y-pipe made by a exhaust shop. and, the dual 2.25" pipes actually have a tad more area inside than the 3" does...the 3" actually does hold a little more backpressure on the motor than complete 2.25" duals would. nice vette though.

Nixon - i've never been to orlando's track but i wouldn't mind going sometime...atleast its 1/4 mile. when do they run test n tune? how much is it? i'll run your mustang. You'd probably win but i bet my 3.1 would surprise you. i almost beat a guy at lakeland one night that had a mustang like yours, he was running a 5.0 with slicks on the back and did not pass me until we got about 3/4 of the way down the track.

edit: the chart i have say 200-300 hp should have 3" single exhaust or 2.25" duals.

Test and Tune nights are normally every Wednesday and Friday. $10 to observe, $15 to run. It's something like 6-11pm, but I forget..... I did both my runs there. They put me up against a 17 second import....who knows why. It was nice. I saw him in my side mirror. For about 0.5 seconds. I think it was a different driver cause I raced the SAME guy twice...talk about coincidence...yet the first run he pulled a .522, which is very close to perfect...the second run his reaction time was OVER 1 second. See the timeslip I'm attaching...I'm bored.

By the way...I've got 2.5 duals on mine....makes ~225 hp at the wheels, so around 250-260 at the fly. I'm a little lacking on low-end torque though until I hit 3000 rpms.

3" single flows a tad better than 2 1/4" duals, IIRC