Attaching a smooth firewall over an existing firewall?

[4DSEVEN]

Has anyone ever welded on to their existing firewall rather than cut the section out? ie. instead of cutting the old firewall out, I would just weld a new smooth piece on in front of it like a plate.

I would like to go with a shaved wall but am hesitant on the task at hand if I cut out the existing wall. I was thinking of the idea of welding a new firewall in front of the existing.

Stupid idea?

[sgtusmc]

As long as the firewall is rust free. i don't see any problems with a skin. My uncle did it on his 59'El Camino. He welded up the borders and used some type of adhesive in the middle areas. I've seen the stainless steal and diamond plate also, and I think it looks good. I guess if you took that route, adhesive would come into play.

[BT Classics]

Good question. Going through that idea right now with the '56.
Do you have to weld or how good is metal panel adhesive? It is supposed to be good for attaching quarter panels, door skins, roof skins and such.

[hotrodrookie]

I was thinking about this too on my truck and I have seen on guy on here use the welding over like a plate method, but I guess it comes down to preference. I would rather cut it out and butt weld in new sheet metal and know that its the same over the whole firewall. Or, you coule use polished diamond plate and rivet them on both sides of the trans hump.

[joeys66pickup]

mine was filled in with Fiberglass and Bondo!! if your go9ing to do it, Do it Right! grind down the old one then primer the **** out of it before you attach the new smooth one.I would rivet it but thats me

[hotrodsbyray]

BT Classic - the automotive body panel adhesive is VERY strong. It holds many of the panels on new cars together. Be sure and use those made for automotive body work, available at most paint and body work suppliers.
I had some left over on and old project so I glued a 1 x 1 foot piece of steel over about a 10 inch diameter hole. After it dried I took a sledge hammer and pounded away (great for relieving frustrations by the way). I ended up tearing a hole in the 18 gauge metal before the glue gave way. I wish I had taken some photos of all that.

[cajundragger]

i kind of did that on my truck.

I welded all the way around the edges and drilled holes in the middle to rosette weld it.

then where ever it felt loose or anything I just drilled another holes through the front layer but not the rear and welded it.

I did prime both the original firewall and and the new piece with primer and used weld through primer in the areas I expected to be welding on.

[4DSEVEN]

Originally Posted by cajundragger

i kind of did that on my truck.

I welded all the way around the edges and drilled holes in the middle to rosette weld it.

then where ever it felt loose or anything I just drilled another holes through the front layer but not the rear and welded it.

I did prime both the original firewall and and the new piece with primer and used weld through primer in the areas I expected to be welding on.

Cajun do you have any pic's of your progress by any chance?

How far to the top edge did you cut? I was wondering if I would go about a 1/2" down from the top lift but it would then have a small ridge.

Also in terms of your rosette welds did you do many of them if you recall?

[cajundragger]

I don't have any pics really.

but I left my original firewall on the drivers side down to the column mount, then cut out the stock engine recess, then cut out across the passenger side. I left like 1/3 of the original firewall there and sheeted over it.

I probably did like 20 or so welds. plus the bead I did all the way around the edge. I brought my sheet all the way to the rolled edge of the firewall so it was easiest to make the transition.

[OrrieG]

Not metal but Brothers make a plastic or fiberglass cover that glues in place. For metal you could weld stud on the back and bolt thru the stock firewall at the stock heat pad locations.

[JML55]

I welded mine over the existing fire wall. I drilled holes all along the lip and welded from inside the cab for the upper edge. The lower edge i just welded along the seam. Drilled holes for the hood hinges and heater core hoses.

[BIG CHEVY 3600]

I don't know what year you have nor what engine you will be running but if it is an AD and a V8 you may find you will need the hump in the middle of the firewall so your dist will fit. I just welded all the holes up and smoothed it out with a little Bondo. For me that was easier than other options.