Thread: firewall replace welding question

Tweet

DO NOT grind that rolled edge off!!

I think they're talking about smoothing the flange surface of the inner portion of the opening, as in taking off the burrs from drilling out the factory spot welds. You may need to go around with a hammer and dolly and straighten up some of the cowl edge so that you meet the flange of the new wall as evenly as possible. Once you've got the new piece in it's place (helpful to use several vice grip clamps) all you should need to is plug (or rosette) weld at each of the spot weld holes. That was what held in the original piece, should be plenty for the replacement. Unless the rest of the body is unstable for some reason, or if you've moved it around since cutting out the old firewall, it should be pretty much in the right shape. It wouldn't be bad to do a cross measurement of the opening before beginning welding to make sure it's square though. Also, if the flange on the new wall doesn't want to sit quite flat against the old cowl flanges in a spot or two (like the corners) a small tack weld to hold it down won't hurt. You can dress the weld later, and then do a nice, neat seam seal job and it will look better than new.

Here's what it should look like when you're done (before the seam sealing).