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Q. Last weekend I was replacing the cab corners on my '54 GMC. I ended up with about a 1/16-inch gap, and was having trouble filling it in with the TIG, so I switched to the MIG. It all started out pretty good; I had to use a copper backing plate in a couple of places, but I always seem to want to rush it and end up with warping. It all looked good at first, but I ended up with about a 1/4-inch groove for about 3 inches. Will I be able to pound that out from the inside? I still have one side to weld, and I got the gaps a lot closer on that side. How long do you let the metal cool before making another tack, and how far apart should the tacks be?
E. Moline, IL
The proper spacing between tack welds for patch panels is usually between 3/4 and 1 inch.
A. To minimize distortion, keep the heat in the panel as low as absolutely possible. The very best technique is to let the panel cool all the way down to room temperature before adding another tack weld. I'd start by making tacks about 1 inch apart. Some people complete the weld by just adding more tacks to the already tacked areas, one by one. This is a slow process if you allow it to cool completely before each new tack, but it is the best way to minimize warping.
There's no problem trying to bang out a weld from the backside. There are several factors that affect how much the metal will move, such as the contour of the panel and the size of the weld bead. You'll find out pretty quickly if it will (or won't) move! If you can't bump it out completely flush (I'm doubtful you can), you can always use a little plastic body filler to smooth the panel for painting.
Q. I have several areas on my vehicle where some prior shade tree bodyman has beaten the hell out of the steel and left it like a bag of walnuts-stretched, lumpy, dents in, dents out (and of course, filled with Bondo). Am I better off cutting an area like this out and welding in new steel and dealing with the distortion around the new patch, or am I better off attempting to bring this area back into decent shape? Come to think of it, I suppose I could try improving it first before I give up and cut it out?
By the way, when I took your classes, I was a die-hard oxyacetylene man, and thought TIG welding was for girls. BUT, having since purchased a Thermal Arc 185 inverter, I am now so impressed with TIG-it's easy to use (if you are experienced with oxyacetylene welding, at least), clean, and precise-very nice!
Via the Internet
A. Good question, but there are a lot of variables here. Generally, I take the approach that I think will give the results I want in the least amount of time. If you're not quite sure, it is always better (as you surmised) to try to fix what's there. If it becomes just too difficult, or too time consuming, you can always cut the section out and replace it.
I started using TIG as my primary welding process in the late 1960s, and I've never looked back!
Q. I am getting ready to install an independent front suspension on my '48 F-1. I understand how to measure and mount the crossmember. My questions are: How do I measure the placement of the motor mounts? I will be using the 5.0L from an '82 Mustang GT. Will the upper and lower A-arms from the Mustang fit the IFS or should I just buy the ones to fit the IFS?
Fort Polk, LA
A. Not all IFS kits are the same. I suggest you contact the manufacturer to see if the stock Mustang control arms will fit-most aftermarket manufacturers have designed their IFS kits based on the stock Mustang geometry, but not all.
If your kit didn't come with instructions on placing the motor mounts, you'll have to position the motor yourself. One of the most convenient ways to do this is to bolt the transmission to the motor, and using a chain hoist, lower the assembly into the engine bay. Ideally, you should be able to fit the package into place allowing sufficient clearance at the firewall and radiator (use the stock fan if you can), and you'll have to position the tailshaft of the transmission in a spot where it is convenient to build a mount for it. You'll also have to make sure you have enough clearance around the starter and the steering box, and that you have enough room to run the exhaust system. Do a check on the steering linkage, too, so you won't have any surprises there.
Once the engine and transmission are properly positioned, block them into place; then you can take measurements, and make patterns for the front motor mounts and the rear transmission mount. Have the motor centered with the front mounts at the same height and make sure the carb base on the intake is level.