i'm interested in some thoughts from others about the size of the exhaust tail pipes.

i have on my car right now 2 1/2" pipes from the headers to some california turbo mufflers (they are old now about 7 years and they are split at the seems and they are leaky) and it stops there at the axle.

now i have some "fullboar" mufflers that are the "full flow" design. they are completely welded and i guess they are knock offs of the the flowmasters.

the fullboar mufflers are 2 1/2" in and out and they are rated at 413cfm's and are rated good to 376hp with 2 1/2" exhaust.

i just bought a complete exhaust set up from a guy who bought it from summit (aluminized pipe). it has 2 1/4" pipes with from headers to mufflers (summit brand mufflers) with 2 1/4" tail pipes. i bought this complete set up that had about 20 miles on it for 50 bucks.

my question is about using the tail pipes with my current 2 1/2" pipes from the headers. and using the fullboar mufflers that are 2 1/2" in and out and using the 2 1/4" tail pipes.

how much would i be giving up in the exhaust flow using the smaller pipe on the tail pipes? my current motor put down an honest 300 hp to the rear wheels and im planning to do some more tunning to the engine combo to increase the performance. but i dont want to go backwards by choking down the exhaust system.

i think the mufflers will open up the exhaust flow over the current cheap turbo mufflers but im wondering if the 2 1/4" tail pipes are going choke down the exhaust and send me backwards to what im trying to acomplish.

thanks for any replys

Jim Hand did some exhaust tests on his 462" Pontiac some years ago and saw very little change from running various tailpipes.

http://www.boyleworks.com/ta400/psp/exhaust.html

If you are revamping your headpipes, be sure to maintain the collector diameter all the way to your crossover. A 6" x 3" collector with a 2-1/2" reducer on the end reflects a lot of waves.

If anything,it will keep the car quiet having 2.5" lead pipes and 2.25" tails and not lose any ET..if it was 2" tails,that would be another story

I just posted a good bit of info about this topic in another topic called 'exhaust....?' Specifically though, one of the mufflers we tested was the FullBoar V-Tube muffler. In the 67 GTO with the V-Tubes we recorded 305hp. When switching to 18" Xlerator 'straight thru' design mufflers, we increased to 315hp peak. Xlerators employ the same design as DynoMax Ultra Flow and Magnaflow mufflers. Yet in another test on the lower hp Mustang, the V-tube picked up several hp vs the better flowing DM UltraFlows. I'm absolutely convinced that if we installed those old turbo mufflers that you have on this combination, the horsepower would drop a minimum of 10-15 below the 305hp recorded. I think that the 2.25 tailpipes are much less of a factor (if mandrel bent) than what is in front of the mufflers and the mufflers themselves.

ccass........so you think i'm heading in the right direction? i figures those old turbos might be holding up some hp. a besides from being old......i thought it wouldnt hurt to change them out with a better flowing muffler......and the fullboar just so happens to be on the shelf at the muffler shop.......so thats why im going to use them and they seem to be pretty close to my hp numbers.........

if anything .....another kind of performance muffler should be better then what i got now right?

and the tail pipes i wanted on there because of the niose inside the cab is bad at about 1100 rpms when just rolling around town.......

i hope my end result is better then what i got now.........i wasnt looking for the best just better and not going backwards........

in fact tomorrow tues 23th im taking the car in to have the mufflers put on (fullboar) and the 2 1/4" tail pipes. i just hope the car sounds ok.

Yes you making an upgrade. I believe you will like the sound once installed. Make sure they either use band clamps or tack weld the mufflers so down the road you can upgrade the pipes without chewing up the muffler ends.

well guys the car is back from the muffler shop.......the guys are good friends down there and they cut me some good deals.......

so as it sits........the car is a tade louder at idle....but not bad.......but the noise is all behind the car.......sitting in the car it is really quiet big time over the last set up...........now you can hear more of the motor while sitting in the drivers seat........

now the drone noise is completely gone im so pleased with how quiet the car is inside........while just cruising around......

now the down side..........the car is louder then before by way more when the gas is to the floor.............so i guess i better keep my foot out of it.........

the mufflers i could see thru them some they are off set in and center out and you can just catch some sight from the other end......the tubes inside looked perforated and seem to stop way short of the full length of the case of the muffler........so i guess why they are going to be loud since the exhaust doesnt seem to have much in there way to get out...........

i dont think i step back with these......but it is more noise then what i was looking for..(full throttle that is)......o well ........if they get on my nerves i guess i will try something else..........

by the way is it possable for the change in the exhuast system have anything to do with they way my car idles now? the reason im asking is because my car has been set to idle at 1000 rpms in park and right at 700 in gear.......just because its cold out.........i have the mixture set for hot motor (warmed up) so when its cold its wanting more fuel, so it has a low idle choppy idle and the more the engine warms up the more smoother the idle gets..........

anyway the engine is now running right at 800 rpms in park and 500 in gear........completely warmed up.......so the idle is now different......im kinda wondering if maybe its being leaned out some more since the exhaust is freed up...........

So are you running 2.25 pipes into the mufflers and 2.25 pipes out of the mufflers? Does the car respond better and feel like it has more horsepower?

Originally posted by gared69:
So are you running 2.25 pipes into the mufflers and 2.25 pipes out of the mufflers? Does the car respond better and feel like it has more horsepower? im running 2 1/2" pipe from the headers to the mufflers, the mufflers are 2 1/2" inlet/outlet, just the tailpipes are 2 1/4"

i really have not ran it hard or nothing since i put the exhaust on. because after i got done with the exhaust i had fresh tires put on the rear. didnt want to burn them off yet. it sure sounds like it could be faster :D .

my next step is now to get my cam phased in,since the cam is way retarded in my engine.