i was thinking about purchasing some larger tube runners for my 91 formula but i dont know if they are really worth the cost....do they add enough power to notice? and where will they help out...low end or top end???maybe some of ya'll may know ...thx
91formula

To be honest, if you have a CAI, exhaust, a cam, and some tuning you would possibly notice a little. If not, then you would be going a little far. If you plan on going all out with your car, then by all means.From your tech tray you only have some tranny work. Is that all you have done?

Matt

ya i only have tranny work but im eventually going to get some more done...i sorta want a cam but then again im not sure cuzz i dont know what it does...and i have the stock dual exhaust....i also want to get a chip and maybe some gears but not too high..i was thinkin 3.23's maybe...and i might buy a nitrous kit from a buddy here shortly....

runners will give u more noticelable hp increase on a 350 TPI bc the intake is super restrictive bc it is designed for the 305, runners alone can give u 10-15 hp but combine with a basplate etc u get alot more, 18-20 hp runners and baseplate on a stock 350 from edelbrock...thats conservative. port the upper plenum to match the runners and remove resitrctions behind TB and then upgrade the base maybe do some minor port work if u feel like it and u can get 30hp, add more fuel with a adjustable fuel pressure regualtor set at 50psi and upgrade the exhaust and u got alot of power. expect almost .4-.5 sec increase in 1/4 mile from intake mods, and .5 sec in 1/4 mile from exhaust, just dont do the intake till u do the exhaust! getting all that new air in doesnt do much when u cant get it out bc the exhaust on our cars is horrible.

do the exhaust first then the intake etc. 40hp from a moddified intake is capable and a buttload of torque as well, exhaust mods complete headers, ypipe, high flow cat and catback can get u 50hp and 25 at the wheels. runners are a good choice and worth the money if u do more mods but a stock engine will benefit still.

Sorry to be the bearer of bad news, but there is no stock dual exhaust on your Formula. The exhaust manifolds both enter into a common y-pipe that turns 2 pipes into 1 that runs the length of the car until it enters the muffler. Then the muffler has 2 exit pipes that come out on each side, giving the apperance of a dual exhaust. Cosmetically, it has duals, but mechanically, only a single.

well yes...the exhaust runs down from both manifolds all the way down the car into its own cats and everything until the rear of the car, they then run into a muffler that has 2 cans on it and splits to each side.....i can cut the joining pipe between the two cans and weld them shut then i have aMECHANICALLY DUAL EXHAUST....

What? Sorry to be so dumb, but I can't follow...

Don't feel bad BBJ, that doesn't make sense to me either.

what im saying is that the pipes are single intil they BOTH (singally) run into the exaust cans at the rear of the car...then they SHARE the exhaust cans....

Do you mean that you have two inlets on the muffler? Sounds to me like an "H" pipe configuration.

Matt

well all i can really say is that there is a muffler on each side of the car ...and they are connected together by 1 joining pipe....and the two other exhaust pipes run into the joining pipe when they meet the rear of the car...

Anybody remember the early 3rd gen. ('82-'84) performance exhaust? It sounds like 91formula may be describing something similar. I can't remember exactly how the pipe/s were routed from manifolds traveling backwards towrds the rear of the car, but I do know they had 2 mufflers mounted horizontally under the rear bumper cover, something like a C5 Corvette. Kinda wierd looking and very restrictive, hence the change to 1 large muffler with 2 outlets in the mid '80s. Maybe that's what we are talking about, not sure though. One thing I know for sure, stock style exhaust on all '91 f-bodies includes 1 exhaust pipe that runs length of car right beside driveshaft slightly right of center, then over rear axle where it enters 1 large horizontally mounted muffler located in the middle of car under rear bumper cover, then a pipe exits each side of muffler and comes out 1 on left side and 1 on right. Maybe the 1st Firehawks were different, but I don't think so. Can't say for sure...

I'm not trying to be arguementative, just trying to picture this in my head. That's it, a picture would be worth a million words in this case. Also, don't forget, exhausts are one of the first modded things usually, so maybe the exhaust in question is just not stock anymore.

well the exhaust has had some work done to it by looking at the weld job at the cats and piping..but it looks by far high performace or aftermarket...and just like C5 corvette has its exhaust is just like mine....one muffler on each side of the car at the rear and the 2 pipes join into the pipe that connects the mufflers together and then 1 pipe on each side of the car comes out of each muffler.....thats the best i can desribe it but ill see what i can do about a picture soon for you....

yes on the 1991 formula with the 350 it goes into a colector after the the manifolds just under the passangers feet but at the seat it comes back to two differant cats and two seperit pipes them down the car.

What?

Pictures would help me because I feel lost.

The correct original exhaust for a '91 350 Formula (and the hi-po 305s) is from the exhaust manifolds into the downpipes each one connecting into it's own catalytic converter. Then the pipes from the two converters are merged into one pipe that runs along the tranny tunnel, over the rear axle on the passenger side and then into a transverse/crossflow muffler and then out exhaust outlets on the left and right sides. The exhaust you're describing with two mufflers is indeed the early '82-'83 thirdgen exhaust system that is quite restrictive compared to the later design. If you want to wake that car up get a set of headers (Edelbrock has a kit specifically for dual cat cars),high flow cats, and a 3" cat back exhaust system to replace what's on there now. You won't be disappointed.