Technical *Let's talk about welding thin tubing to thick exhaust flanges!*

Do you weld tubing to the flanges from the outside? Inside? Both? It depends?

I'm MIG welding my Tudor's exhaust system & started by tacking 16 ga. tubing to 1/4" 3-bolt flanges.
I've welded from the outside and have what looks like a good weld, given the bead's shape & bluish colored HAZ.
But looking at the inside (the gasket surface), It's obvious I didn't penetrate hardly at all.

I think I should weld a bead around that edge too, then grind & file it flat. What do *you* think?

Thanks, fellas.

 

A good weld on the outside should do it. But for insurance a small bead on the inside and grind smooth would not hurt anything. Remember, after welding, it’s probably going to have some warpage in it anyway.




Bones

 

Gary,
It's too late now, but I would have inserted the pipe half way through the flange, and fully welded it on the inside, and ground it flat. Then skip weld it on the outside. In your case you probably need to weld, and grind it flat.

 

Personally , I would go with a thicker flange . Look at what header manufactures processes are as well. I would weld as you described then smoothing welds flat so you get good gasket sealing properties. Hope you check your flanges that they do not get warped. There is a thread on here, with good advice from other hambers. Good for you doing your own work.

 

I would have ran the heat and wire up to handle the 1/4" thick metal and pulled the weld puddle into the lighter tube as you went along.

 

As said,concentrate heat on the flange and 'pull' it to the tubing. The only penetration discoloration should be on the tube. Its not structural anyway..

 

I bolt the flanges to the head and tack the pipe on the outside, then unbolt it and weld the inside.

 

Put flange at top of tubing----weld it---grind it flush.

 

Hmmmm. I suggest you grind a bevel around the inside of the chosen gasket side of the flange, and insert tube as you see fit. Then spot weld around the perimeter, and grind to smooth. That'll give you a larger area, and larger associated bead.

Just my opine.....Roger

 

I as always weld the tube inside, nothing but a tack on the outside.

 

That weld looks solid to me and better than most of my booger welds, but I'm no expert. I would never have thought about welding from the inside. That 1/4" plate looks kinda thin to me, but pics can be deceiving. Also, with the weld that close to mounting holes, it might be challenging to install.

 

Welding the inside also helps "dig" into the gasket for a better seal.

 

I think brazing those joints would fill the void completely to prevent any pin holes and should be plenty strong for a header. Less heat would result in less warpage too. Any reason not to us brazing instead of weld?

 

Heres what i would do if i could weld.

 

I weld on the inside only.
On my race car, I used 1/2 inch thick flanges and O-ringed them before welding.
No need for gaskets that way and they never blow out.

 

If I had a welder, and if I knew how to weld, and if I had a Bridgeport end mill, and if I knew what I was talking about, I would probably camphor the I.D. of the flanges and lay a righteous bead in there on the outside.
But I don't, and I can't, and I don't, and I for sure don't.
I might not be a professional-quality welder but I did stay at a Holiday Inn last trip, and I know enough not to put anything I welded on my car................ and not to give welding advice.

 

I’m just getting ready to make some turn outs, so thanks for the timely question and answers. I like the suggestions to push the pipes through the flange, weld the inside, then grind flat. That should result in a suitable seal and a nice clean look on the outside.

 

It should have been tack welded on the outside, and a complete weld on the inside.

 

Gary. I have done this both ways making headers. Inside, outside and both. They all have worked fine. Its your call.

 

Thanks for the advice, guys. It's *REALLY* appreciated. 30 minutes of welding, grinding and filing and I'm ready to move on.


I'm welding the 16 ga primary tubes to 5/16" header flanges next week.
Will attack them from the inside (gasket side) per @Marty Strode @Lloyd's paint & glass @Deuce Daddy Don @Blue-Collar-HotRods @Robert J. Palmer @OLDSMAN & @mad mikey.

 

You will get it done correctly