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Press Forming Tube for Exhaust Flange

Twisted Minis

New Member
I got my header flange from Hot Rod Chassis last night and it gave me an idea. I want to use 1.5" tube for my header, because thats what I can bend, and it matches my cones from Cone Engineering. As you can see, it doesn't really fit.

So last night I though I might be able to make a die to press the tube over and force it to take the form I wanted. I found an aluminum square that was close to the size I needed, so I ground it down real quick and tried it with a piece of copper pipe. It made a pretty rough square, and galled the aluminum a bit. But I now know it could work, and it also showed me what kind of space I needed to leave for the tube to form over and provide a good gap.


I found I needed to leave about 3/32" between the die and the inside of the flange for the tube to fit well. So this morning I started building a die out of steel. It needed to be 1 3/16" wide on one side, and 1 5/8" on the other. Not having any large blocks of steel, I cut three pieces of steel 1 5/8" wide at the bottom and 1 1/4" wide at the top. I used two pieces of 1/2" plate and one piece of 3/16".

I cut them larger than I needed, because I'm not that great with the plasma on thicker stuff, and needed them to be smooth. So I got out the 9" grinder and went to town until they where all roughly the same size.

I then welded them together with the 3/16" plate in the center of the two thicker plates.

I then proceeded to grind the blocks until they all matched. Then I raduised the corners to match the die as best I could, and did some finish grinding with a 4.5" grinder and a 120 grit disc.

I made sure it fit inside the flange well, and adjusted it as needed until I was satisfied.

Now time to test it out. I coated it in some low heat lithium grease to help the process, and make it easier to remove.

I then pressed the other side of that same copper pipe onto the die.

The die was easy to remove with a hammer and a brass punch. It left the tube looking like this.

I tested the fit, and I was happy. It fits very snug on the back side of the flange, and left a weldable gap at the front. I think if I press the tube on just a little farther I can tighten the gap at the top so I can TIG weld it.

I didn't have any thin wall steel to test this with, but I wanted to post it any way. Steel gets delivered here next Monday so I will report back when I try it in steel.
Hey, your doing a nice job, I make exhaust flanges for all my own stuff. In fact I am doing a T-bucket right now and am about to the the exhaust on it. I will post some pics if your alright with it. Look forward to see how yours turn out.
Nice fixture. I made mine out of 2 pieces of 1-1/4", 12g tubing welded into a V shape about 4" long. Didn't have a press, so I just set 'em on the table and drove them in with a dead blow. Try a piece of 1 5/8" tube, you might find a better fit with less work.

I tried 1 5/8". I did it in steel today (forgot camera) and got a near perfect fit. Plus the 1.5" I can bend, and it will provide a little more back pressure, and it matches my cones.
Here's the swedge I made for mine and the flange for my lakes headers. The header in the back is for the days I feel like bein' loud!


Kind of a detail thing for me. Besides, I used the stock header flange gasket as a pattern for the new flanges.

RPM said:
I know the ports are kinda square. But why not just use a round flange and save all that work?

Because you want the transition to be as smooth as possible. Going from square to round instantly causes turbulence. I've always been told to match the ports to each other for the best results. If I just went with a round tube half of the exhaust would be hitting a wall.
If you go to your local gun shop and get a tube of Lee Case Forming Lube you can use the lube on your press form buck and the inside of the primary tube. The lube is powerful good stuff, its meant originally for deep draw forming auto panels. Its also really good for double flaring brake pipe.
Took a while for me to remember to take a picture, but I did it in steel with pretty good results.

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