macx

If I put on a dual hump trans mount (either a stock pre-80 or aftermarket), then would a dual type setup from a pre-80 fit?

Thanks!

UKPaul

I don't know for sure! But I fitted a Bowtie x-member for a 200-4r tranny which gave a lot of clearance for pipes. The x-member is tubular, with a hump on each side to allow exhaust clearance. There is more clearance on the p.side than the stock x-member has & this clearance is also mirrored on the d.side. I don't know if Bowtie make an x-member for a stock '81 trans but if they do, or can, it makes the fitting of duals much, much easier. One problem I had is that the d.side floor pan sits quite low so, even with the pipe as close as possible to the pan, I've only got 4" of ground clearance at this point.
I've been told that fitting an earlier x-member will allow "normal" duals to be fitted, which makes sense, but the lower floor pan might be a problem?
:cheers:

IRON WILL

I can't remember where exactally I saw this exhaust system. It was either a Ecklers or Mid America Catalog. It is true dual exhaust, and you can get aluminized or stainless steel. Both pipes are run under the passenger side floor where there is extra clearance. I believe it comes in 2-1/4 or 2-1/2 in pipe. You'll have to look at their catalogs as I do not see it online. Dynomax also offers a true dual exhaust system for that car. You can get more info on their website about it. I had mine custom bent. You can cut a notch in you stock crossmember, but you have to add metal in the notched area in the crossmember for support.

UKPaul

Mid America do a dual system which is 2 1/2" and fits well. I had one on mine until I fitted Headers & made a custom system up. It worked well, gave a nice seat of the pants improvement & the guy I sold it to seems happy with it.

Fast81

One thing you have to be careful with is WHERE the X-member mounts to the frame. GM moved the mounting around slightly for deeper floorpans/different tranny options.

HOW DO I KNOW THIS??: The 82 X-member I bought for my 700R4 install into my 81 mounted 4-6" further forward than the original TH350 brace = floorpan interference. Solution - custom mod to original X-member :banghead:

Glensgages

UKPaul:
Why didn't you just 'mod' the M-A kit to work in conjunction with your headers? Too much fabricating?
I'd 'like' to run the S/S M-A kit with headers, unless I'd be cutting-up too much of the M-A kit.
Winter is coming, & I'd like to get the parts here soon.....

UKPaul

Initially I was going to remove the MA front pipes (their system is 2 pipes/side) & get pipes made up to run from the Headers to their rear pipes, joining very close to the cutout in the x-member. Being an '81, with both pipes passing under the x-member on the p.side, it would have meant a very tight bend on the d.side pipe. While lying underneath I suddenly realised that the Bowtie x-member had clearance on both sides for true duals :)
So, rather than splitting a perfectly good MA system, I made a system from scratch. I wish I'd taken a pic of it as it would be easy to explain, but what I did was to make it out of 3 pieces per side & another piece as the "H" crossover. For anybody interested I joined all parts together by spreading the pipes with a pipe expander (not easy on thick walled stainless) & slotting them together. This also gave a bit of "adjustment at each join. The 1st pipe on each side was a short length with a 15 deg bend in it. This had one end expanded to fit over the reducer on the Headers. The bend then brought the pipes up parallel to the underside of the car (the collectors point down). I then got another 2 pipes about 2' 6" long & welded short stubs on them after cutting to shape. Then drilled & ground out the metal inside the "stub" to make the "H" pipe join. Both ends of these pipes were then spread & they were slotted onto the pipes on the collectors (hope you're following this! I'll get a picture ASAP!). Another pipe was cut to length, had the ends spread, & was slid onto the studs to finish the "H" pipe. Then I got 2 long pieces of pipe & got them bent to an angle of 85 deg (several attempts were needed to get that angle right!). Sliding these into the "H" pipe & aiming them down the underside of the car to pass under the rear spring either side of the diff allowed them to join onto the mufflers after trimming to length. I then jiggled the whole system about as I clamped it all up with exhaust clamps. The mufflers are angled perfectly at the rear & both are symmetrical.
The "H" pipe may have helped performance (?) but it's definately taken the edge off the sound at WOT (with Monza glasspacks WOT was real, real loud!).

So for the cost of 20' of pipe (the min length I could buy) I've now got a custom exhaust in brushed satin stainless :) I had to pay for 4 bends, which is the exact amount of bends needed to join my Headers to the rear of the MA system. The only real problems I had were expanding the pipes for the joins, but from reading this forum it looks like you guys have a whole bunch of places that'll do it for you.
:cheers:
edit: I guess the '82 is the same, with both pipes running under the p.side? As I understand, the 80 & 81 had manifolds with a 2" restriction, but the 82 manifolds had a full 2 1/2" restriction, so Headers aren't as important? What I found was that fitting the MA system onto the stock manifolds "seems" to have given a bigger SOTP increase in power than swapping the stock manifolds for Headers. I'm not sure that I've got the mixture correct yet, but the Headers have definately helped performance at high rpms.
The simplest way to fit Headers and duals, without altering/changing the x-member, would be to buy just the rear pipes from Mid America (if they'd sell them on their own). Then you'd "just" have to get some pipes fabricated to join the Headers to them. BUT the pipes will run very close together & parallel under the x-member, which would be an ideal place to fit a custom fabricated "X" pipe :D It should work out really neat, but it would depend if you could get some pipes fabricated & also on whether MA would sell 1/2 a system. Good luck, & if you do get duals fitted you'll wish you'd done it earlier!


[Modified by UKPaul, 11:30 AM 9/25/2003]

mvftw

I just replaced my exhaust with a true dual (no cat) 2 1/4". I bought the dual trans hanger. Also don't forget to replace the studs and take out the heat riser.

Fast81

UKPaul -- I've been looking over the MA true dual system for awhile (just waiting until I'm emissions exempt). My question is this: even though both pipes run side-by-side on pside under the tranny x-member, there is no "X" or "H" connection between them ?????? Wouldn't this be an easy thing to fix ??

Master Ho

Yes, you could do either config, but there isn't much room between the pipes.

Fast81

Looking at the pic on their website, it appears the MAD true dual hooks right to the factory system over the rear axle and to the mufflers..............correct ???????????

Master Ho

Yes, the config from the (former) cat back is the same. The only difference I could see was the left downpipe crossing over to the rh side, to clear the x-member. This might be a good area for the x or h pipe, or a simple "semi-U".

MIKER

I chose to modify the existing cross member on my '80.

Cut out a "C" shaped piece and fill the void by welding in a split open section of exhaust pipe.
The transmission mount on this same crossmember has also been modified to accept the 700R4. Both mods were easy to do and basically didn't cost any money.

UKPaul

The MA system practically follows the same route as the stock system. You just bolt it to the manifolds, run it under the car & connect the mufflers at the other end. OK, it's not quite that easy as you'll need to do a bit of jiggling about, but it's a fairly easy job. An "H" pipe would be quite tricky to fit in the area of the x-member, but a custom made "X" pipe would be a simple job to fit where they run very close to each other under the x-member. What I planned on doing was getting 2 short lengths of pipe bent into a flattened ohm symbol (or a side view of a snail!!). Then I was going to cut an oval out of the "hump" on each pipe & then weld them together (getting the bends & cut to keep them the correct distance apart).
Or you could make up a solid "H" pipe with the pipes very close together & a short joining piece between them & slot this into the system at the same place. I can't weld, but it looked an easier job to make an "X" than a squashed "H" & an advantage is that an "X" pipe flows better than an "H".
Or an alternative is to do what Miker has done & run an earlier system.
:cheers: