I have researched as best I can all the offerings for 2.5" exhaust systems. I am almost finished building my "visually" correct 400 for my convertible. I will be running long branch exhaust manifolds. I want to be able to install the system without having to add a spacer to my cross brace (if possible) and have the correct shape for the tailpipe over the rear axle.

I have spoken with the major suppliers. Pypes was the most vague about the fit and "correctness" of the tailpipes. Gardner will supply a concourse correct 2.25 system - too much $ for a daily driver in my opinion.

Please give me some feedback on what some of you have done/used on your FGF's and which mufflers you recommend and why. If the best answer is to have a local exhaust shop custom bend the exhaust, I will do that.

Thanks!

Tom

i vote for local w/ 2.25" pipe. you can bring in your own mufflers to some places. Dynomax are supposed to be good.

some places/techs will only custom bend, and it might come out the way the tech thinks it should rather than the way you do. a tech who is unaware that the pipe goes above the crossbrace may run it below.

many places have specs on all the pipes, and can use the specs to bend it like factory rather than complete custom, or even do a combination of custom and factory style bends, giving you a 1, 2, or 3 muffler system for your bird... maybe even a front crossover.

you can call and ask prices and whether they can bend to factory specs or not. (have 'bend cards'). also ask about their mufflers and if you can bring your own. usually you will get a better price over the phone, but it always goes up once you add in hangers and clamps and any extras (like crossover) you want. just remind them the base price they gave you on the phone.

one company i worked for had Ravin mufflers which were very solid in construction, and, at the time, were carrying a lifetime warranty. their regular mufflers were garbage. the Ravin was similar in construction to the Flowmaster, but sounded different. some people didnt like the sound and preferred Flowmasters. i was the opposite.

I went with a custom exhaust from a local shop. Duels from the exhaust manifolds all the way back including mufflers $250.00 (2.25") Very close to the floor there are no exhaust components visable without getting down & looking.

Tom , you`ve seen and heard mine...former owner installed 2 straight pipes 2.25", w glasspacks then I added TA splitters (later model, 70`s something..)
sounds amazingly good , esp. after I switched to the 5C heads , exh sound changed w the larger valves..

I did my own, just bought 2 8 foot lengths of 2.5 inch aluminized tubing and had the shop chop them up into 3 or 4 pieces each and bend a 4 45s and flar the ends so I could cut and slip fit the pipes. I then installed my header collectors , used 45s to turn toward the driveshaft, cut to length and fitted the next 45 to run the pipe straight down either side of the trans tunnel. I also put in an H-pipe about 1.5 inches back from the 45s that tunred the pipe straight. I then used Flowmaster DeltaFlow 40s and dunped the exhaust in front of the rear axle. It is LOUD, but that's how I like it..... You CANNOT see any pipes from the side of the car as they are tucked up close to the floor and in the trans tunnel a bit. To see them one would have to lay on the ground and slide under the rocker a little.

Unless you want to so some cutting and welding to get the fit you want from a mailorder kit I'd have it custom bent locally.

Drew

If you're going to go down to a 2.25" duals (which you will on the convertible if you don't want to space anything) you want mandrel bent pipes. Anything less is sacrificing hp for the 400.

I've yet to find anyone in my area that does mandrel bent custom exhausts. Most use compression bends. Either that or they have to cut and weld prebent sections which can't be cheap either.

Summit does sell a mandrel bent aluminized 2.25" exhaust. Does it fit a convertible? Don't know.

heres one of the ones im looking at.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=7932469431&ssPageName=STRK:MEWA:IT
the 68 i just bought is too quiet. i wanna hear the 8v but not too loud. several companies sell the kits but dont have them so i wont comment.

let us know what you go with and how it sounds.

Drew, if your pipes are not visible anywhere you are likely to get headaches, the exhausts will possibly 'draw' back into the coupe....if not exhausting beyond the body.....back draft...
in safety minded Sweden you cant even get inspected w/o the pipes outside the body...not sure about it here, esp. if 25 yrs and older...but if you drive it long drives (like to Shiner...lol) and get a headache ,thats probably it...check it out....(possibly this saturday...lol)

So your saying that the exhaust pipes should run above the crossmember ?

no, but on 'verts they run above the floor x-brace.

here in the US the tailpipe exit style laws vary state to state, and so does enforcement. some may say where the pipe can exit, specifiying X" behind passenger compartment or X" behind rear axle. vans, pickups w/shell, schoolbuses and station wagons may be required by law to have the exhaust exit out the side rather than straight out... at least this is what i picked up bending pipe in LA, IL, MO, and NC. i think they are included in the emissions laws, but i just did what i was told. i never actually looked them up.

I have the PYPES 2.5 inch X-pipe system on my 68 with V-Tube mufflers. Mine is not a convertible, but I know of several people running this same setup on their convertibles, they all say it fits good.

I went with custom on my 'vert, pipes above the x brace. There is a photo on the link in my signature. I am very happy with the sound and workmanship.

I went with the 2.5" PY down pipes and x-pipe kit for long branch and Dyno Ultras. Pipes went together in a day. That's taking off the old and installing the new(manifolds too, just turn-downs). Had to cut off a little to fit from the head pipes. Love the sound. Didn't seem too loud when finished but after all day of cruising my ears were ringing a bit. Oh and it's a coupe so I don't know about the brace clearance. I would recommend.
Robert

Tom, it's a hard call... now just how close to factory are you going? Are you wanting it to look just like factory, or to look like a good clean dual system that would like right to most who would ever see it?

Factory would be something like 2.25" from the manifolds, tuck up under the X-Pan (for the vert) and into two resonators, then up and over into a dual in/out transverse muffler, and dual exhaust pipes out the back.

If your going for something that will look right or period correct, but not 100% factory, then I would look into the total cost and time on both systems (local shop and Mail order) and from there, you'll have to make sure the local shop can do the work the way "you" want it to look.

Most good local shops (read independant shops) will have the experience and know how to give you a better fit and finish than a mail order (more generic) system. I found a good shop near me that I will have do one or two more of our cars before I have them extend the Firebirds pipes all the way out the back (turn downs before the axle now)

It may cost a little more in the end, but the work will be solid, and probably fit better, and look nice and clean (welds instead of clamps etc...)

So let us know what you decide, and maybe some pix of the end results?

Good luck - Brett - 67 Drop Top 455!

Trans tunnel is sealed and pipes dump just in front of rear axle. The pipes turn down into air stream under the car. I'd be more worried about it sitting in traffic for a long time. Otherwise, windows down allows plenty of fresh air circulation.

Shiner will be a good test.

D

My system is just what Brett described, except the dual tailpipes exit under the quarter extensions where the old ones did. As they project only an inch and a half or so, you don't really even see them.

Thanks for all the input. In response to Brett's question - I am not looking for total concourse correct. I want it to look "correct" to the average person, but give me a little more in the performance area without sacrificing the fit of the pipes through the cross brace under the car. I like Vikki's system and may go that route if there is no way to put a 2.5" system in without shimming the cross brace as Pypes recommends. I may have to print out Vikki's pictures as a reference.

I think I will drive it to a local exhaust shop before I swap the engine and have them take some measurements and see if they can run a 2.5" system or I will have to settle for a 2.25" system.

Again, thanks for the input. I will let you know how it turns out.

Tom

the spacers dont have to be large to run 2.5". i just ran 3/8" nuts as spacers on cars i ran larger pipe on.

you could even run 2.5" back to the brace and then go to 2.25" through it. that would give a little more room for the gasses to cool and contract before going to the smaller pipe. i did something similar over the axle on a roadrunner once... 3" down to 2.5" for the u-bend, and then back to 3"(for the look).

large exhaust increases power by moving the peak up in the rpm range, but this also reduces low end power a bit. a modified engine often should have larger pipe, but a stock engine does not usually need it or necessarily want it. exhaust flow will also be a factor in optimum carb tuning. (very important on motorcycles, not so much on cars)

if 'performance' for you is top end, or you are on the highway alot, go with 2.5". if you prefer low end, go with 2.25" unless you have a larger than stock cam and high flow heads. (IMO) the difference may not be very noticeable other than sound, dyno runs, and race times.