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Old 01-15-2012, 02:26 PM
Brian Martin,Freelance adviser
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Originally Posted by matts37chev
me and butt welding dont get along

however, I will do this

O.K. lets see if I got this

1) I'm thinking I will trim it so it is about 1/4" in/down, from the roll/beveled edge of the body line

2) screw it down tight and if I need to I can use a hammer to tighten up the gap before/as I weld

I pretty much knew both of those (steps 1 & 2) just double checking

and to clarify #3)

3) .... I can do very short , hot welds? (cooling in between)
I dont have to do endless tack welds? like when I put on my lower front repair panels?

4) grind, smooth and pretty when done welding
And let me clarify my opinion on the butt welding. Of course butt welding would be the "best" way. Overlapping a half inch lip of the old firewall around the edge like I am suggesting would be the "bestest" way.

And yes very short little welds, a 1/4" at the most. And please be sure you LET IT COOL, not "cooling" it as you just described.

And remember when you weld you need to cut off the wire so each weld you are hitting the metal with a nice, new, sharp wire so the arc is started immediately so as not to waste heat, unwanted heat trying to start an arc. Hit it with that nice sharp wire and WHAM you are doing a little 1/4" weld in a second or two, literally a second or two at the most. Hit the underlying metal first right and then bring the arc over to the edge of the new firewall. When you are finishing this up and you are welding next to a previous weld you hit right on the underlying metal next to the weld then go up onto it and over to the new firewall.

If you want to tackle butt welding we can go over that in detail as well. The most important thing is of course a super tight fit with no gap. You can do that by trimming some more of the new firewall off, about a half inch or so. Then screwing it to the old firewall. Scribe around the edge with a sharp scribe so you get real close. Then cut the lip of the old one off at that line, on the INSIDE of that line so you can see the line and very carefully trim it down so you can just see the line, that would be close enough to start trial fitting the new firewall and filing or grinding it to fit to perfection.

But honestly, no one is going to be pulling your firewall insulation out and looking how you welded it as you are driving down the road with a smile on your face proud of a job well done.

But again, I do agree it is the best way to do it.

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