Welding Tips and Tricks

I'm installing new wheelhouses on my 66 mustang convertible. The picture below shows where the brace from the rear trunk divider to rocker panel mates up with the wheelhouse. The brace is 14 gauge (green) and the wheelhouse is 21 gauge (silver). It looks like the factory might have done it with a torch. I assume I want short beads spaced out along the length of the bracket like the factory. As you can see from the second picture, the fit up is pretty tight so there are no gaps to fill. I'll hammer and dolly as I go along to make it as tight as possible

I'll be doing this with a mig welder. I'm a self taught and pretty good with most welds. But, on this one I'm just not sure what the best approach is - favor the 14 gauge, favor the 21 gauge, setup the welder for 14 gauge, set it up for 21 gauge, push, pull, weave, etc. Positioning is going to make viability awkward so that will make it a bit harder.

I asked this question on a mustang forum and got two opposite answers (one said favor the 14 gauge and the other said favor the 21 gauge). I'm leaning towards setting the heat for the 21 gauge, favoring that piece (i.e., the back piece), and let the heat melt in the edge of the 14 gauge. Obviously, I will clean the metal before I weld.

Any comments and suggestions would be very much appreciated.

Rick

I would think the closest match to factory original would be to drill the 14 ga. for rosette welds to simulate resistance spot welding. Short stiches will certainly serve the purpose, though, and seam-sealer will blend the welds in, anyway.

Regardless, MIGging this on such thin material should (IMO) be done as a series of stacked spot-welds. I would slightly favor the heavier material, but with careful spot-welds it won't make too much difference. Be patient between overlapping spots, skipping around.

An advantage to the stacked spots is a greatly reduced overall heat input for less warping/distortion. A disadvantage is in having the experience to know how long a "spot-time" to reach sufficient penetration, so some scrap from the rubbish bin should be worked out and destructive tested to increase your confidence.

Just some thoughts.

Steve S

Otto - thanks for the reply.

I've attached an additional picture showing some additional information about the factory welds. The area of the bracket that makes contact with the wheelhouse is very small (varies from about 1/16" to about 3/16"). I would describe it as a flange on the edge of the bracket. So, plug welds are not possible.

From the appearance of the original welds, it looks like they were done with a torch. I could use stacked spot welds (tacks), but I'm concerned about them cracking. On one of Jody's videos he said tack, tack, tack = crack, crack, crack. So, I'm thinking a continuous bead 3/4" to 1" would be best.

I'm going to work on this tomorrow and as a first step I'll take some scrap 14 gauge and 20 gauge (don't have 21 gauge) and mock it up and see what I can work out. I can probably get it to work favoring either the 14gauge or the 21 gauge. I asked the question hoping that someone with more experience than me could tell me which would provide the stronger weld. Given the flex in the body, there will be some stress on the welds.

I think the answers here pretty well covered the important points. The only thing I would add would be that you need to skip around; do a bit at one end one side, a bit at the other end other side .. and so on.