rashort <rashort@swbell.net> wrote:
: Most shops use oxy/acetlyene for exhaust, because it's easier to control
: burnthrough and it's also easier to bend the rod and fit the torch into
: tight places. Cheaper too. I've used a mig to weld many exhausts, but
: you have to run the bead in strips. It's next to impossible to weld
: continuously around a 360 degree pipe with a mig, which leaves more
: possibilities for leaks, but as I said, it CAN be done. It just won't be
: pretty. Most shops that I know of use migs to tack pieces, then they go
: back and weld them oxy/acetylene.
That's true - a disadvantage of MIG when welding exhausts is the
general lack of clearance, and also the fact that most MIGs generally
don't weld very well upside down. However, I have also seen the results
of shops which weld up the exhaust with oxy/acetylene when its still on
the car - the previous owner of my Cuda had this done and it was a real
hack job. There are probably people who are good enough to get away with
it, but IMHO, the exhaust really should be dropped down away from the
vehicle to weld it up.
When I am welding up an exhaust, I put the pieces in position on
the vehicle and hold them in place with a few tack welds, then I
unbolt them and let them swing down or just remove it from the vehicle
altogether to fully weld it up.
I developed a technique for MIG welding exhaust pipes which works
very well for me - instead of laying down a bead which will probably
look messy and/or burn through, I "stitch" it together with a series
of what are more or less spot welds. I start at one point, and keep
going around the circumference of the pipe, overlapping each spot weld
by about half a weld's width. It is strong, creates a good seal,
is much harder to burn through, and looks decent. Here's an example
from when I was doing an exhaust for my '96 Dakota last year:
http://www.jonsteiger.com/www/misc/dakmuffler/IMAG0003.JPG
Another tip: after the exhaust is welded up, I like to hit the weld
with a wire brush or wheel, then top it off with some high temp exhaust
system paint (1400-1500 degree). That should help to keep rust at
bay since the heat from the welding will burn away the aluminized coating
and the pipe (and weld) will start to flash rust almost immediately
unless protected from the elements.
As far as my welder goes, I use a Hobart IronMan 250 which is a 220V
welder with a built in cart and bottle stand.
(http://www.hobartwelders.com/products/IronMan250.html)
Its a nice versatile unit which can use standard or flux core wire,
can weld stainless with stainless wire, and with the addition of a $250
spool gun, can also weld aluminum. A bit overkill if all you will be
doing is exhaust tubing though.
---Jon-
.---- Jon Steiger ------ jon@dakota-truck.net or jon@jonsteiger.com ------. | I'm the: AOPA, DoD, EAA, NMA, NRA, SPA, USUA. Rec & UL Pilot - SEL | | 70 Cuda, 90 Dak 'vert, 92 Ram 4x4, 96 Dak, 96 Intruder 1400, 96 FireFly | `------------------------------------------ http://www.jonsteiger.com ----'
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