Hello,

I am new to the V8 world, recently bought me a Trans AM 1988 2 door hatch back with a 305 TBI. As it stands the car has a stock exhaust system which is setup kinda weird like. It comes off 2 headers, into a y pipe which them goes to the back end and routes into a muffler with 2 pipes. I can imagine that this is heavily restrictive so I was thinking.

I was thinking of getting performance headers, HiFlow catalytic converters (to keep the emissions low) and 2 hi flow mufflers. What kind of performance should I expect from such a mod?

 

if u just got a nice set of headers (like hooker or slp, etc..) and got a nice 3 inch high flow cat and then a nice catback like hooker then it would quite a nice sounding and flowing system.

 

These cars really weren't meant for dual exhaust. Trying to cobble something together will end up making you unhappy, especailly considering how low these cars are.

A mandrel bent 3" system will flow the same amount of exhaust as a dual 2-1/4". A 3.5" system will outflow a dual 2.5" system. It's just simple physics based on the volume of the pipe.

Use a good set of headers, y-pipe, high flow cat, and a good cat back and it will be like driving a different car.

 

really.....i have dual 3" exhaust.....and many people on this board have superb and cleanly engineered dual exhaust systems.....read the dual exhaust pictures thread.

you just have to know what your doing.

you can go up to a 2.25" dual following the stock exhaust routing in most cases.....

to do a 3" you need to go under the rear axle similar to how the exhaust runs on a vette.

heres mine.

 

ground clearance is fine really....heres the pipes not on the car.....kinda dirty and crap from some oil and fluid leaks that exploded on it a few times.....

 

ah ah ah dont talk about stuff till ur sure
i have a 2.5 inch dual running the stock trail (talk about a tight fit)
but it does not rattle at all
i realy have to get off my *** and take some pix of my finished exhaust

 

ah ah ah yourself.....i am sure, and you need to read more carefully

dont put your mouth in gear, if your brain isnt engaged

Note that i said "in most cases" after 2.25 it gets very difficult

 

Where I live, you would watch that dual, under the axle set up flip out from behind your car with all the pot holes and medians. I have Hooker Long tubes into 3 inch that y's into a 4 inch pipe over the axle into a 4 inch race magnum Flowmaster. A good y pipe and 3 inch over the axle will flow PLENTY good enough for ANY street able car.

BTW-- I like the dual set up I'm just offering an option because the dual setup would cause ground clearance issues where I live.

 

no offense man, but
dude are you high?
i live in new england north of boston, home to the worst roads in the free world.......it never hits, cause its not that low

its hit on speed bumps with 2 220+lb people in the car before....if you arent going slow enough.

and not to bust your chops, but there are plenty of streetable cars that can push more exhaust than a single 3" or 4" pipe can flow......mines one of them.

my exhaust is almost straight with no cats and its dual 3".....and i still see a 2-3mph pickup with the mufflers open.....you run that through a single 4" pipe, its gonna choke

 

to be exact it was not difficult at all i did not have to do any body modifications to fit the exhaust just a little bang here and there for the flowmaster 40s sitting right behind the bumper

i guess some people think that thinking is very difficult (u must b one of those special window lickers) congradulations

 

come on guys..I just made this post cuz I was wondering if it would be a wise first mod...lets keep this friendly.

 

ThraxXx: I was thinking about doing the exact same thing to my car, but I have a 350 TPI, so I was considering 3" dual, but I wonder if I should settle for 2.5"... Then I decided to ditch the cats, as Hawai'i doesn't have emissions testing.

If anyone has sound clips of a 3" dual setup on a 350, I'd like to hear them, that and 2.5". I'm not looking for super-loud, just throaty. That and some more seat-of-the-pants, get-up-and-go action.

But ThraxXx, I'm saving the exhaust work until after I iron out the kinks in the suspension first - power only is good if I can get it to the ground.

 

your just irritated because you were put in your place.

fit 2 3" pipes through there and then maybe someone will think your talented

 

just an FYI...I won't be doing the work cuz well...I am mechanically retarded .. I will probably contract out to a local performance shop to get the job done.

 

if your not using a really high flowing head, a large cam or both....you should be fine with the 2.5" pipes.....they should flow enough to not be a restriction.

once you start sucking, and spitting out more stuff (bigger heads bigger cam) then it becomes an issue

 

ok. So Exhaust isn't a good thing to start with? What should I do for my first mod?

 

well it can be, it all depends on the big picture......

if your just starting out, i wouldnt worry too much about it......you have to start someplace, and exhaust is pretty simple

 

Forget about the dual exhaust. It is way unnecessary. Just get a nice set of headers/Y pipe, good cat(s)., and a good 3" cat-back or something a little bigger from a company like mufflex, or any exhaust shop with a mandrel bender..... if you're gonna be putting out more than 300 hp at the wheels that is. All the dual exhaust pictures I've seen on this website look like crap on our cars. Just go with a nice magnaflow, slp, or hooker cat-back and be done with it.

 

Ok...Thanks for the advice man.

 

I have an IROC Z28, and the ground clearance on my car is very dimunitive, even with the stock springs. The catalytic converter on my car scrapes going over certain hills, and speed bumps. I have Edelbrock headers & Y-pipe, stock cat (gutted), factory mid pipe, and a Dynomax muffler and tailpipes.

I couldn't even imagine trying to run true duals on the car, because I've spent a lot of time under it, especially when installing my T56.

Besides the fact is that there's no real reson to run a cobbled together dual system when there are so many high quality bolt on systems that will free up a ton of power and cost very little to have installed. The single setup makes just as much if not more power than a dual system would anyway.

One thing to keep in mind is that a cross flow muffler robs a lot of power. The systems that exit on the driver's side make more power than the ones with a factory style muffler and dual tailpipes. Another option is the Borla system that has a tuneable cutout channeled into the right tailpipe before the muffler, and then a regular tailpipe on the left after the muffler. You still get dual pipes out the back, but it performs like a single outlet system. Best of both worlds type deal.

BTW, exhaust is a great first mod for these cars. Keep it in reason though. Stick with 1-5/8" headers and a 3" single system. 1-3/4" headers and 3.5" systems are available, but will rob torque on a stock engine. If you plan to change the heads, intake, and cam at a later date then installing the bigger stuff up front isn't necessarily a bad thing. The car just won't perform up to it's potential until the supporting cast is on the set.

 

Yeah, he said it best.

 

id like to flow test my "cobbled together" dual 3" exhaust system which was built by a reputable racing exhaust shop against any "bolt on" aftermarket single pipe with a single muffler

or *****'s superb dual exhaust system, or any of the other 1000's of people on this site who have one.

and for the 200th time....ground clearance is not a problem.....if you think it is, its because you've never put one of these systems together correctly, or been under a car that had one.

just saying so illustrates that you dont know what your talking about

any good exhaust shop can build you a top dual exhaust that will not cause any ground clearance problems, and give you 2 mufflers that will flow far better than ANY single pipe for a fairly reasonable price

you can do what you want, but i prefer to do things right.

and its not very nice to disseminate poor and incorrect information to people that dont know any better.

 

On a TBI car ? It's, arguably, one of the best things you can do for it. TBI exhaust has to be the most ****-poor exhaust the fine folks at GM ever pulled out of their rears.

Unless you are good at fabrication/welding, which you've stated you don't have a strong inclination for, duals it beyond what you want or will even need for a long time.

Duals are fairly (IMO) easy to make and make well with good ground clearance, it's a matter of skill (or $$paid to someone with skill) and attention to detail which makes or breaks any system. Some people who make dual system don't really care if a single is 'just as good'. Sometimes there are other reasons for making a dual setup. None of it matters if it's not on your car.

The man really just wanted to know if getting rid of the (crap) TBI exhaust is a good first mod on his (assuming) stock car (since he said he just got it) and yes, it's a good idea.
Quit making it a pissing contest guys.

 

O.K. bro, you win. No sense in arguing with you, I know what's right, and that's all that matters to me. Yes, Thrax, to answer your question, pretty much anything is better than what you have now.

 

of course....thats why all the fastest cars on the planet have single exhaust anyways

 

You seem to have a serious problem with people disagreeing with your opinions.

I don't appreciate you implying that I don't know what I'm talking about either.

I repeat, and I'll shout this out for the cheap seats, MY STOCK EXHAUST DOESN'T HAVE ENOUGH GROUND CLEARANCE.

Your car may be different than mine in terms of static suspension height. You may not have a problem with your system, but I do with mine. I'm not wrong, I'm not immagining things, and I certainly know what I'm talking about.

Dual 3" vs single 3", duh. Obviously the dual system flows more, but that's not the point. A dual 3" system is total overkill for a stock motor. Even a 2-1/4" dual system is probably too big for the wee-o-five. A single 3" system will build more torque though.

In the end everyone is entitled to their opinion, you've got yours and I've got mine. Opinions are like that nefarious body orriface. We've all got them and they all stink!

 

Umm...sorry, but on review of all this, you seem to be the one rudely arguing 383. And I will again STRONGLY disagree that all dual system outflow a single system.

From all of this, I am gathering that Thrax just wants something that is much better than what he has now. I don't think he is trying to turn it into a race car. I'm also assuming he wants something practical, therefore, a single is best for him. Note, I am only assuming all of this.

 

If you have ground clearance problems with your stock exhaust its either not installed correctly, your car is lowered, or your ride height is otherwise too low ( worn suspension maybe)


and once again, smaller diameter exhaust DOES NOT BUILD MORE TORQUE.

its been dyno tested a million times....its not an opinion its a FACT.

the freer flowing your exhaust is, the better it is for both torque and HP at all RPMs

if you put a bigger pipe on, and lose torque its most likely because the manifolds or headers are not ideal for the combination.

scavenging is created by the exhaust pulse being timed properly (by tuned header primary lengths) to pull waste gases from the combustion chamber......having a larger or smaller pipe does not influence the timing of those pulses.

what this boils down to is....if your headers are scavenging correctly.......and your pipes (after the collector) are big enough to flow without restriction that is where you will produce maximum torque........at that point you could put a 12" pipe afte the collector and it would make very little difference

look this topic up in a search on the exhaust board, its there someplace.....if you dont think its true, try it on a dyno and see for yourself


im not trying to be a jerk here.....ive done this before, and learned the hard way.....im just trying to explain how this really works.....this is a very common misconception.....thats why the monster truck runs zoomies.....

 

My car isn't lowered. It's a stock IROC Z28, which sits about an inch lower than a normal Camaro. The suspension has been thoroughly gone through, and it is in top working order. The exhaust is installed perfectly with all the factory hangers, and a cat hanger I had to cutom design and fabricate for the T56 swap (a stock '95 hanger I sectioned 1.5" and a custom built cat hanger). I have a fairly steep approach to my shop, which is really the only place the car scrapes regularly, but it is annoying nonetheless.

Pipe size after the header has little to do with anything except max flow. I agree. It's header primary pipe size that really affects power production, as well as primary pipe length.

Header collector length in an open system does have an effect too, but is mainly used to fine tune the powerband.

 

just run turndowns