Fast81

Hello- I've been reading about all you fellow Sharks running around with dual exhausts. Presently have Dynomax coated headers with hi-flo cat and chrome-tip Monza mufflers............stock setup "Y" into/out of the Cat. Will duals with X-over be a big improvement over this configuration?? Are there any bolt on kits available??


Engine mods listed in sig block
:steering:

Fast81

sorry - new to this.

Engine mods: AFR 180 heads, Crane 1.5 RRockers, EBrock RPM-AIRGAP intake, Performer cam, Holley Projection TBI, TCI 700R4

battsup

2.5" duals will be a big improvement over anything with a catylytic converter. I personally dont have an H pipe or and X pipe and wouldnt change my current configuration.

jaybird81

I have The true dual set up from Mid America with Flowmaster mufflers. I don't have headders or a X pipe. I am happy with the way the car sounds, I now noise is relative but I think it is LOUD

69Sting

Personally I am running Hooker headers to side pipes. POO on the whole cat hing.

I was involved in circle racing for 8yr and did some read on exhast configeration, X is the best method to max exhaust flow with H being the second best. What the X and H pattern does is allow for exhaust to find the easiest and fastes way out of the pipes so you can put more down with out back loading the motor.

I would think if you want to run the exhaust to the rear and knowing how much wounderful space to work with for exhaust the H patern would be your best bet. I would also get rid of the cats, those take a good amount of performance away.

If you like side pipes, popular set up is the Hooker headers to side pipes. This will get rid of your cats and mufflers and add in another security factor. Anyone you don't like to let ride in you don't warn them and they will burn their legs on the pipe. After that they don't want to ride anymore :cry

Ganey

See what many refer to as my Exhaust topic. http://www.corvettefaq.com/c3/ganeyexhaust.htm

If you have the Performer 2102 cam, more cam is needed.

Fast81

Thanks for the heads up Ganey!!!!!
I thought when I added the AFR's I'd need more cam, but bolt on ease won out over total perf (and I didn't have the time to pull the engine to swap the cam). I'm definitely adding a CompCams 262XE with a rebuild becomes necessary.

:steering:

Fast81

Also on a related subj: the floorboards get quite warm in spite of the heat shield mats under the carpet. Should I wrap the Y in thermal wrap ?? Would this toast my cat?? How about wrapping the Y to the muff's?? I know most header manuf say wrapping voids their warrantee, why?
:steering:

Ganey

Probably rust. For cooler floor, remove or add opening(s) to duct to side vent. If you are going to run a converter, then dual converters are rec.
It might be possible to get away w/ one mounted as a crossover. :rofl:

:cool:


[Modified by Ganey, 8:57 AM 8/22/2003]

UKPaul

My '81 had a new stock system on it when I bought it. The cat had been replaced by a piece of pipe. I fitted a Mid America dual system, initially with the stock mufflers, & the performance increase was definately noticeable. I then fitted Monza mufflers and, while it got a whole bunch louder, I'm not sure that performance improved by much.
I then fitted Dynomax Headers. As I had a custom x-member (from Bowtie) I had room to run a pipe down each side, so made up a system from 2 1/2" stainless pipe. I fitted an "H" pipe in it which took the edge off the noise. It's still loud, but the x-over has made it a more mellow sound. Just for info, the pipes needed a 15* bend to bring them back to horizontal after connecting to the Headers. Each pipe then runs down each side of the car, aiming to the side of the diff where there's a gap below the rear spring. Then an angle of 85* was needed to hook each pipe into the muffler. The "H" pipe was fitted just by the tranny x-member (you wouldn't believe how much effort it took to get those angles correct :( ). It works well, apart from only having 4" of ground clearance due to the drivers floor pan being so low.
As you've got Headers it would be a waste buying a MA system, just to cut it up to fit the Headers, which leaves 3 choices:
1) get a system made & run both pipes down the p.side so that they fit under the x-member. Where the pipes run parallel next to each other it would be a perfect place to install an "X" pipe.

2)The real problem with duals on an '81 is that x-member. Here's a pic of the Bowtie one for a 200-4r, with the stock one below it:

Apparently an x-member from an earlier Vette fitted to an '81 will also allow true duals to be run (one down each side), or you could make a custom one up or modify the stock one & then fit true duals.

3) See if Mid America will sell just the 2 rear parts of their 4 pipe system. Then take the car with the 2 pipes to a decent exhaust shop, get them to remove the stock system, fit the MA pipes to the mufflers & then bend up some pipes to connect them to the Headers (& maybe even make/fit an "X" pipe in there.... duals with Monzas are very, very loud at WOT without some sort of x-over pipe!).

However you do it, getting rid of that horrible "Y" pipe will give a big improvement :yesnod:
:cheers:


[Modified by UKPaul, 9:41 AM 8/22/2003]

Fast81

How do you get an exhaust shop to touch your Vette without the Cat being present ??

Since I already have the headers and the entire system is sound, would having the Y's cut and connected with two 2.5in pipes work (following the stock routing and also MAD true-dual path)?? Otherwise, I'll just order the MAD kit and cut back the fronts to match my Dynomax headers.

How about keeping the cabin cool?? Wrap the duals under the cabin section ???

Pauld

I just bought the 2.5" stainless steel MAD system from UKpaul and fitted it this weekend and all I can say is WOW!! The difference in performance and sound is fantastic, only draw back is that you can't keep your foot off the gas, just have to keep hearing that lovely sound!!! :D :D

mvftw

I just had 2.25" true duals, no cat, no heat riser, H-pipe, & S/S Flowmaster 50's put on...very happy... :D

Fast81

Pauld and mvftw - what did you guys upgrade from??? Stock?? stock with hi flow mufflers?? stock with no cat?? headers and mufflers with a cat??

I know Pauld doesn't have to dodge the EPA ****'s across the pond, but did you do the install yourself mvftw??

:steering:

mvftw

I had the stock exhaust system still in... 25 years old. The car is all stock. I went with this system because the next owner can go back to the 2 - Y pipes and cat if they want. But for cruzing I had to modify it...

Fast81

Did you install yourself or have a shop? If shop how did you get them to do it, I know some won't touch your car without cats....................
Don't you have to have it inspected or pass an emission check??

Here in ohio, I'm not exempt for another 2 yrs (MATH 2003-1981=23). State doesn't bother you any more after 25.

Pauld

I upgraded froma total stock system, I have kept the stock mufflers but will change these to flowmasters when they need changing. I only kep the mufflers because they are nearly new and it seemed a waste to throw them out when they are nearly brand new. Strill sounds great though. :D

mvftw

I had a shop do it. Took over 5 hrs, lots of bends. Plus I had new s/s studs installed and a new tranny hanger (for dual exhaust). I didn't buy a kit because they are made to go to the heat riser, I didn't want the spacer either, I went to the manifold. The cat isssue...cash talks :yesnod:

Fast81

Theoretically, how much $

The_Dude

Local shop just quoted to me around $500. He also said that he wouldn't do it unless I brought it to him without any of the current exhaust system.