Fabricating A 4-Branch Manifold From Stainless - Welding Advice

[Thomas77GR]

Being a restless spirit I've been toying with the idea of fabricating a tubular manifold with downpipe to match the rest of my stainless exhaust.

I thought maybe I could buy pipes with bends and cut/weld them with my mig. Apart from the stainless wire do I need anything else?

I've got a clarke mig. We have a machine shop at work so suppose they could also help with the tubing and plates

Has anyone done something similar?

[611]

Easy enough to do (not sure on the stainless welding bit as not done any!) once you have the main flange that fits to the head made up the rest is not to bad. I did a 4 into 1, not easy as the A doesn't have much space to fit it all in :-) Retro Power might have some tips for you? Its working out how to fit it all in around the steering column!!

Andy

[opelmantagsi]

Just get a retropower one and be done with it. TIG welded and simply brilliant in design and manufacture.

[nickincrete]

you need to use pure argon gas for a decent job

get as thick ss as you can as ss is quite brittle and can crack

some ss manifolds use ss expansion bellows (tvr does this) to stop cracking

set the mig up on scrap to weld as best as poss before final welding, i would tig it as less weld build up

take care if you blow a hole you will put weld build up on the inside, v bad for flow

try to have the ss tube fitting together as tightly as poss otherwise you will get too much build up inside the tube

its quite easy to make one but quite difficult to make a good well flowing one

[Retro Power]

You can weld stainless tube with mild steel mig wire and co2 gas, but obviously it will rust round the welds. you can use stainless wire and argon in the mig, which again will be fine, but hard to get in to certain welds, and looks messy compared to tig welds. Use a decent grade of stainless for the pipework too, I use 316L

[mantadoc]

4 into 2 in to 1 give a better spread of power and torque

4 into 1 give a narrower band and it shifts up and down depending on the tube lenghts.

Pulse tuning hasn't been mentioned and you are as likely to hit magically bad lengths as good ones so a 4 into 2 in to 1 potentially has less down sides.

When you put pipes into collectors you weld the end of the pipes together first and run a fillet weld up each side in the valley between the pipes and make it long enough so that the collector does not cover the weld, that way you don;t have issues with leaks in the bits you can't get the welder into between pipes.