View Full Version : Welding exhaust flange

01-30-2008, 08:35 PM
I just got my new resonators today and a new exhaust flange for it. They are all 304 stainless. I will be replacing the resonator on my gmpp exhaust which is stainless. I have experience welding but not much with stainless. I have a mig welder (HH140) withe the correct wire and gas for stainless. I will be getting some extra pipe to practice on so i am confident i can weld in the resonators but i am a little worried about the flange.

Will i use the same setting on the welder for welding pipe to pipe and pipe to the flange? I am afraid i would burn through the pipe if i went any hotter but if i didn't i might not get a good weld into the flange.

My second question is how do i keep from warping the flange? Many small welds and move to opposite side each time?

What needs to be done to the car so i can weld on it safely?

I can get the flange welded by a professional tig welder but it might take a while and i am impatient. I would like to get the resonators on this weekend. Is the flange going to be hard enough that i will want to wait for him to do it?

Rocky D
01-31-2008, 01:15 AM
TIG welding the flange will warp it slightly more, but the weld will be smaller. MIG welding stainless takes just a tad more heat, but keep the heat on the flange, and let is wash over to the pipe. To keep the flange flat, you could bolt another flange to it, or a plate twice as thick as the flange, or just straighten it with a hammer afterwards. Do not continuously weld around the flange in the same direction, you will lose location...weld it in quarters.

01-31-2008, 07:19 AM
Thanks for the advice

01-31-2008, 09:04 AM
Is there anything special that should be done when welding it in quarters? Like do you weld the opposite side you just welded, like torquing lugnuts? Also, I think you wrote about weld direction to avoid distortion on another post? Thanks

Nick :cool:

Rocky D
01-31-2008, 11:23 AM
Yes, there are a few ways to do it, and as always in welding, it is the results that governs the procedure.
One way is to start at 6 o'clock, run to 9, then 12 to 3, then 6 to 3, then 12 to 9. There are other variations, Like 6, 9, 12...6, 3, 12, half at a time. Meterial thickness has a bearing on it too,...you will get more warpage on thinner material....but then it is easier to straighten, after.

Steve Crum
04-13-2008, 11:00 PM
I frequently do various SS flanges but sometimes I have some assemblies that take special jigs, so figgered' I'd wait and post one that is more or less simple.
This assembly is intake ram tubes for a John Deere model 70 gas puller with the duplex carburator. These pull cool air up from underneith the tractor. The jig is 6" heavy channel with lock plates and bars. The flange is securely bolted down to the channel to help control warpage and the preformed pipes are locked solidly in alignment. All the welding takes place in the jig and cooling is allowed to take place while still in the jig. In most cases only about .005" needs planed off the flange face to produce the mating surface.



It maybe a little overkill on an antique puller but I outfitted another of this guy's tractors last year and he took one of the national championships

04-14-2008, 01:38 AM
Steve Crum has the ticket! Rocky's procedure(s) are necessary, even when bolting the flange down securely. Pay attention to Rocky's point about welding the flange, letting the heat and wire "lick over" onto the thin pipe...and Steve's point about allowing it to cool completely in the jig (metal moves a lot during cool down!). Make a simple mounting plate if you can find a piece of heavy metal to drill.

I assume this is an inline flange (??). If so, use your old flange to mate to the new one with tight bolts, that will help some...and I would put a set of vise grips mid way between the bolts, and remove those only when it cools, then go back and do a couple final "fill-ins" where they were. Because its not a header flange, where flow behavior is critical, you might find a short stub of exhaust pipe that "just fits" inside the new pipe, and leave enough stick out to slip into the hole in the flange. This will give you a backing piece to pretty much prevent blow-through.

If it were a header flange, I'd say go dig up a scrap head, mount the flange(s) to it.:)

Steve Crum
04-14-2008, 12:33 PM
This is how it turned out, a shame the customer did not want to spend the extra 25 bucks each to have these polished, but he wanted them glass beaded. probably to paint them. Like in racing, the pullers don't like to make performance enhancements readily apparent.



Things like this I'm told can add 3 to 4 horses on the dyno and often add a few more inches in a 300' pull. Those few inches are often the difference in a championship and a quiet ride home.