Stainless header questions

[Tonyorlo]

I recently built my first set of headers for a LS engine swap. I put a 5.3 LM7 into my 85 Porsche 944. To buy headers for the conversion, it was $2000 for stainless long tubes, which seemed expensive for my taste. I’ve always wanted to make my own headers so this was the perfect opportunity. I made pvc mock ups and the bought matching 16ga 304 stainless 90s and U bends to match. After getting them tacked together with my mig, I went to town tigging them. Everything was back purged with argon.

My question, for that situation would I have been ok to fuse the metals together, or does it need fill added to it? I tried both, and would really like to hear opinions on it. I will be honest, I was very very happy with just fusing it, but I was afraid it wasn’t correct. I could make it look really good just fusing it.

I didn’t take any pictures of the progress, and now they are in the car so I really can’t get them now. I just would love to hear some thoughts on it.

Thanks!

[Welder Dave]

Filler metal adds reinforcement and also helps clean impurities. No filler makes the tube thinner at the connection and more susceptible to cracking. Some weldors will use Mig wire for filler on thin material.

[albrightree]

I've done a fair amount of stainless tube, by hand. Jobs that I've done by fusion only no filler last longest in applications with no stress loading, or vibration. Really tight fit up , purging, will help when fusing without filler, but cracking isn't uncommon. Its a crap shoot, is it worth having to fix the crack, thats up to you to decide. When I add filler , I get far fewer issues( I don't want to say never ). Thinner wire is readily available in 308, and 316 .035" x 36" tig lengths. I've seen guys using the orbital set-ups for sanitary tube that don't add any material, but I don't know the exact process they use to prevent cracking (perfect fit up/ annealing..etc.) I guess if you do get some cracks, you can always repair with some Hastelloy, 312 SS or some other crack resistant stainless filler wire.
Sometimes I sand a little bevel on tubes when welding in place on a machine because it helps me see the joint better when I can't get in a really good position to see around the tube/pipe.

Got any Pic's , post them if you can.

[arcflash]

Stress relieve them when you are done welding. We hang them with the collector down and run a rosebud into them while banging them with a rubber hammer.

[Tonyorlo]

I really wish I would of found this site before I started that project. I am sure I would of had a better outcome.
I would say 90% of the joints had filler, but ones that fit very tight I did experiment with fusion. I don’t recall off hand the size of filler wire I used, but it was small. Not as small as mig wire, and not wire would have been very handy in most of the joints. I did watch some videos of sanitary applications where it was fused with no filler, but like you said albrightree there is no constant vibration or stress in those applications usually.

I didn’t stress relive them, and I probably should of.

All great advice! I plan to make many more headers in the future so I will just take what I learn and hope the next set turn out a little better than the last. Thank you for the replies!

[camfab]

I started welding about 30 years ago, because i couldn't find a header for my then IROC with the right fit for my heads and swap to a manual trans. I took gas welding and by the end of the first semester of class I had built my own headers. I sold the car and still have those original headers. The welds look they were TiG'd, ah the days of eagle vision..... Anyway, I have a love/hate relationship with stainless. My biggest issue is the fact that it wants to move around so much during the welding process. Like others and yourself, I've fused many parts, and find that it's a fine line insuring that you have complete fusion without a large heat effected zone. Back gassing as you've done is very important. I'd say for the future, practice as much as you can, and add filler rod. It's really your best bet in minimizing the likely hood of cracking. A slip fit collector is also your best friend in crack reduction, but requires the best of fitment. Like anything its all about torch time.