True duals
Thread Starter
Registered User
Joined: Jul 2005
Posts: 747
From: Baton Rouge, LA
True duals
I am contemplating making a set of true duals for my LT1 4th gen firebird. My plan is to put some flanges on a x-pipe (or find one premade with flanges), put the xpipe under the driveshaft and have the pipes run back along the side of the driveshafe (the xpipe is flanged to make removing the driveshaft doable without removing the whole exhaust system)
similar to http://i58.photobucket.com/albums/g2...e_hookerLT.jpg but I will initially be running stock manifolds, I would like to go over the axle and out the back but don't know that I will initially, I will probably flange right before where the mufflers are there and initially run bullets with turndowns and dump before the axle but since it will be flanged I will always be able to swap out later. I have never done an exhaust system before but I have done plenty of welding, I will be using oxyacetylene for this, and just wanted any tips from anyone out there, what kind of flanges should I use? where can I get the flanges to meet the stock exhaust manifolds for now? I would like to save my stock exhaust system because at some point I may move to California in a few years and I will be needing it to make the car legal in cali. and should I use a different welding system than oxyacetylene? I have done innercore and stick welding, I do have access to a mig welder as well however just haven't used it before.
similar to http://i58.photobucket.com/albums/g2...e_hookerLT.jpg but I will initially be running stock manifolds, I would like to go over the axle and out the back but don't know that I will initially, I will probably flange right before where the mufflers are there and initially run bullets with turndowns and dump before the axle but since it will be flanged I will always be able to swap out later. I have never done an exhaust system before but I have done plenty of welding, I will be using oxyacetylene for this, and just wanted any tips from anyone out there, what kind of flanges should I use? where can I get the flanges to meet the stock exhaust manifolds for now? I would like to save my stock exhaust system because at some point I may move to California in a few years and I will be needing it to make the car legal in cali. and should I use a different welding system than oxyacetylene? I have done innercore and stick welding, I do have access to a mig welder as well however just haven't used it before.
Registered User
Joined: Nov 2000
Posts: 1,937
From: Ft. Worth, TX
I ended up doing my own after a hack job was done by a muffler shop.
I too had never done exhasut work before, but had plently of welding experience building my garage.
I used a wire feed with argon gas.
Bought a Jegs 3" universal X-pipe and Jegs 2.5" universal dual set with all mandrel bends. Used the welder, a cutoff saw, and a $25 pipe end expander. I cut the bends just right then welded them back together to get the right angles needed, many of which I did not have to cut at all because the universal kit came with 4-90 and 4 -45 bends.
I made mine with flanges right before the axle so my mufflers could be disconnected easily and removed in case I ever had to drop the tank again for a pump replacement.
Use these Dynatech V-band connections/flanges:
http://www.jegs.com/webapp/wcs/store...0002_753318_-1
These are very strong and seal very well, rather expensive each but well worth it after fuddling with 3-bolt flanges needing a gasket everytime you pull them apart or they rattle loose...
I used Dynatech split flow muffs and Pypes mini cats.
It necks down to 2.5" after the X-pipe. X-pipe had to be cut just right to make the exiting pipe travel parallel with each other instead of exiting at a 45* angle. Took me about 9 hours total to make and install.
Here's what my finished product looked like:
This next pic shows it coming over axle right after the flange disconnects.
No need to have disconnects by the X-pipe, the drive shaft is still easily removed without dropping the exhaust..just drop it out the rear first.
This pic shows the one part too that was a real biotch...getting it over the axle and the right angle to fit on the muff as my muffs could only sit 1 way...notice the series of welds every 1 inch or so...had to basically make a "sleenky" out of little pieces of pipe that fit inside each other that could be easily formed into the right shape and angle.
You'll notice right under the tranny x-member, I made a upside down "T" as a hanger and bolted it to the rear of the tranny tailshaft. The only other hangers are on the muffs using a rubber block and bolting them in existing holes or the bolts holding the bumper on...2 hangers per muff.
Tack it all up on the car, then remove and weld it all the way around to get a good leak proof weld.
Most every joint is a slip fit except the turn on the driver side between the cat and X-pipe and the part that turns up right before the axle. Try to make all of your slip fits so that the edge doesn't protrude into the flow of gases to restrict the flow.....in other words, the rear most / downwind part should be opened wider to slip fit over the previous section/part.
Any other question you got, let me know.
I too had never done exhasut work before, but had plently of welding experience building my garage.
I used a wire feed with argon gas.
Bought a Jegs 3" universal X-pipe and Jegs 2.5" universal dual set with all mandrel bends. Used the welder, a cutoff saw, and a $25 pipe end expander. I cut the bends just right then welded them back together to get the right angles needed, many of which I did not have to cut at all because the universal kit came with 4-90 and 4 -45 bends.
I made mine with flanges right before the axle so my mufflers could be disconnected easily and removed in case I ever had to drop the tank again for a pump replacement.
Use these Dynatech V-band connections/flanges:
http://www.jegs.com/webapp/wcs/store...0002_753318_-1
These are very strong and seal very well, rather expensive each but well worth it after fuddling with 3-bolt flanges needing a gasket everytime you pull them apart or they rattle loose...
I used Dynatech split flow muffs and Pypes mini cats.
It necks down to 2.5" after the X-pipe. X-pipe had to be cut just right to make the exiting pipe travel parallel with each other instead of exiting at a 45* angle. Took me about 9 hours total to make and install.
Here's what my finished product looked like:
This next pic shows it coming over axle right after the flange disconnects.
No need to have disconnects by the X-pipe, the drive shaft is still easily removed without dropping the exhaust..just drop it out the rear first.
This pic shows the one part too that was a real biotch...getting it over the axle and the right angle to fit on the muff as my muffs could only sit 1 way...notice the series of welds every 1 inch or so...had to basically make a "sleenky" out of little pieces of pipe that fit inside each other that could be easily formed into the right shape and angle.
You'll notice right under the tranny x-member, I made a upside down "T" as a hanger and bolted it to the rear of the tranny tailshaft. The only other hangers are on the muffs using a rubber block and bolting them in existing holes or the bolts holding the bumper on...2 hangers per muff.
Tack it all up on the car, then remove and weld it all the way around to get a good leak proof weld.
Most every joint is a slip fit except the turn on the driver side between the cat and X-pipe and the part that turns up right before the axle. Try to make all of your slip fits so that the edge doesn't protrude into the flow of gases to restrict the flow.....in other words, the rear most / downwind part should be opened wider to slip fit over the previous section/part.
Any other question you got, let me know.
Last edited by 2QUIK6; Feb 27, 2007 at 03:19 PM.
Thread Starter
Registered User
Joined: Jul 2005
Posts: 747
From: Baton Rouge, LA
I really like the gasket less stock style flanges, that press the flared end of the pipe up to a bowl shaped flange, does anyone sell flanges like that that can be welded on and if so any reason to not use them? (other than the fact you have to know how to tighten them up properly...
Registered User
Joined: Nov 2000
Posts: 1,937
From: Ft. Worth, TX
I really like the gasket less stock style flanges, that press the flared end of the pipe up to a bowl shaped flange, does anyone sell flanges like that that can be welded on and if so any reason to not use them? (other than the fact you have to know how to tighten them up properly...
Thread Starter
Registered User
Joined: Jul 2005
Posts: 747
From: Baton Rouge, LA
I plan to cut up my stock y pipe and use it to bolt up to my stock flanges (cats already gutted on my stock y pipe and its a single cat pipe so its useless for cali il'l have to get a new y pipe anyway) but it would be nice to use them elsewhere on the exhaust too, maybe il'l just have to search a bit and see if i can find someone who sells them, the flanged pipe wouldnt be too hard to fabricate i dont believe but the other side that it tightens up against I dont have what i need... although there is a machine shop 2 houses down...
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