Body panel repair

[Spaz]

I have a few rust thru spots on my 71. I was noticing some of the pics of panels ive seen were just tack welded using mig. Isthe tack welding on body panels all u need or is it need to be completely welded? Just thought the tack welding was to keep from warping as the panel was welded. Any input? I wanna learn to do this as im looking to keep this truck for a lon time.
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[El Campo]

The problem with not welding it entirely is that years later your body filler shrinks into the cracks and they start to show through the paint. I had my handles shaved by a so called professional and they just tacked it. Sure enough, a few years later and they are all showing. Just go really slow and move around.
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[hugger6933]

Weld it up completely. The tack you may have seen might have been at the start or middle of the process. When I am welding a panel I do small tack and alternate points farthest away from each other. Dont get in a hurry take lots of timethe longer you take in this step will reduce time in the ones following it. I use a heat gun when I weld and take readings so that I know when it is time to stop for a Diet Coke break One of the many used for those little guns[ mainly used to take metal temp so I know when to paint]

[Spaz]

Thanx for the info. I woulda never thought of the temp gun ideer.
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[GASoline71]

It takes about a bazillion tack welds all around the panel to weld it in. Like hugger siad, it needs to be done in alternating spots to keep heat from building and warping the panel.

Gary