[5yearplan]

As far as I know most headers and intake manifolds that are custom made are Tig welded... What would be the downside of Mig welding them instead. Especially as far as the intake is concerned? I am figuring on a maximum of 1.5 bar running through there But probably closer to 1 bar Also, about how much would it cost to have a pair of v6 headers and an intake Tig welded at a shop? Obviously a rough ballpark.

 

[mjr]

The downside would be weld quality. For alloy you should always aim for TIG. As far as the intake side goes, you could use MIG, but would have to be gas Argon/Co2 mix, and at least a 150MIG.Dont even bother considering gasless MIG for this. TIG is far superior both in terms of weld quality and ease of use. The other big actor is welding skills.

 

[PSk]

Agree that for alloy TIG is the way to go, but there is a myth that MIG produces poor welds.

The only reason MIG can produce poor welds is the person using it, they were designed for production line welding and actually produce stronger welds that arc (or so my engineering teacher told us).

I've MIG welded exhaust headers in the past, but as they are designed for production line welding they are not really suited to welding around tricky objects ... unless you are really, really patient. Thus on my last set I just tacked them with the MIG and gas seamed the joints.

I've also used my MIG to weld up a spaceframe chassis AND the suspension components and I have never, ever had a weld failure AND the welds looked beautiful, nice beads, etc. I also crashed this car a couple of times and destroyed wishbones ... but again no welds failed just tubes bent, etc.
Pete

 

[tomgtv6]

I think most mass produced headers are mig welded; only the true custom stuff is tig. Tig takes much longer to do. I have done both in the last 6 months and I will say my tig stuff is better than my mig, and not talking about what they are like as much as control over what you are doing.
Where tig is going to shine is aluminum welding. You need the control. The problem with mig is you pull the trigger and you are welding ;while sometimes you just want the heat with no filler.
Because you are talking about turbo stuff I think I would at least have the intake tigged. Finding a regular welding shop that will tig will be hard most are mig and arc for stuff like iron doors. Tig is $$$, mainly because of speed and machine cost and most customers dont care.

 

[PSk]

A race shop should be able to TIG the intake ... as most race components (engine stuff anyway) are TIG'ed.

Otherwise you just need to find the right fabrication shop.
Pete

 

[mjr]

Actually I have a question re MIG too. have welded on lots of >1mm stuff before without many probs using mainly 0.8mm wire and Co2/Argon gas @ about 25-30 amps low power. I have some repairs to complete on the GTV6,(never welded on this before) and the panel thickness in the area is <1mm, about .7 to .8 mm thick, so thin. My SIP migmate 130 DP takes 0.6 or 0.8mm wire.
So 0.6 or 0.8 wire best for these alfa panels at low power? Im thinking 0.8 may be over cooking things, especially since Sip migs have fairly poor wire feed control as it is. Any comments?

thanks