Smoothing my firewall

[gtotto]

Hey guys,

I've searched the site (and others) for info on smoothing firewalls and found alot of different opinions and methods. I think I have come up with a solution and would like to run it past you guys.

I have a 65 GTO/clone factory A/C with several large factory openings in the firewall. I am planning on running an aftermarket A/C unit so the factory openings will no longer be needed. I could patch the holes and fill the dimples with filler but my main concern is the long, curved, horitonzal seam that runs the width of the firewall. I am afraid that if I try filler or weld on the long seam it may eventually crack and that would be bad.

My plan is to template a sheet of steel to use from the passenger side to just past the vin plate. This would cover up 90% of the seam and the wiper motor and brake booster would hide most of the rest. I was thinking 16 gauge (too thick??) and attatching the panel with adhesive on the low spots and welding the perimeter. I would probably drill a few holes in the panel before attatching it and then plug weld them.

Any input would be greatly appreciated

Thanks
Ken

[gtotto]

anyone??

[Tom Welch]

Do it like that and it will be fine, just got through welding patches over the seam and the ares we had to cut out due to rust on the firewall of my son's 69 Nova. I smoothed the firewall on my 67 Firebird by attaching patches with panel bond, then fiberglass then skim coat of filler, I didnt have a welder then.

[gtotto]

Do it like that and it will be fine, just got through welding patches over the seam and the ares we had to cut out due to rust on the firewall of my son's 69 Nova. I smoothed the firewall on my 67 Firebird by attaching patches with panel bond, then fiberglass then skim coat of filler, I didnt have a welder then.


thanks,
do you think 16ga is a little thick for the firewall......or better since it won't telegraph the uneveness of the original firewall as much

[Tom Welch]

Im using panels from wrecked cars I pulled from a dumpster at a local body shop. I dont see an issue wth 16ga. except that welding may be a challenge against thinner material.

[gtotto]

Im using panels from wrecked cars I pulled from a dumpster at a local body shop. I dont see an issue wth 16ga. except that welding may be a challenge against thinner material.


I could probably try 18ga if 16ga causes any problems

[JRouche]

I used 16ga, really good stuff to work with. A bit hard to shape, but it just takes a lil more time. The best part, its thicker than the stock sheet metal. So you say how is that better??

Well, you could get some 18 or 20ga sheet, and the common idea is to match the original sheet thickness, prolly 18ga. But the thicker sheet allows for some better welds IMO. Why?? Well, you are still gonna set the patch in there flush with the top surface. So its not gonna sit high. But with a thicker patch you have a starting point to weld from, its gonna be the thicker sheet.

Whether its the TIG or MIG. With the thicker piece in there you will start the weld off of that, melt the thinner sheet into it. If you are working from two sheets of the same thickness then the possibility of popping through increases, more filler metal. The original sheet is gonna be thinned, even if you make sure to square the edge off.

So you lay the thicker sheet down, at a flush level with the original metal and focus the heat on the thicker 16ga steel. Tie the two sheets together and its solid. Welding 16ga to thinner 18 or even 22ga metal is a dream. VS butt welding same thickness sheets together. For me anyway. JR

[gtotto]

I used 16ga, really good stuff to work with. A bit hard to shape, but it just takes a lil more time. The best part, its thicker than the stock sheet metal. So you say how is that better??

Well, you could get some 18 or 20ga sheet, and the common idea is to match the original sheet thickness, prolly 18ga. But the thicker sheet allows for some better welds IMO. Why?? Well, you are still gonna set the patch in there flush with the top surface. So its not gonna sit high. But with a thicker patch you have a starting point to weld from, its gonna be the thicker sheet.

Whether its the TIG or MIG. With the thicker piece in there you will start the weld off of that, melt the thinner sheet into it. If you are working from two sheets of the same thickness then the possibility of popping through increases, more filler metal. The original sheet is gonna be thinned, even if you make sure to square the edge off.

So you lay the thicker sheet down, at a flush level with the original metal and focus the heat on the thicker 16ga steel. Tie the two sheets together and its solid. Welding 16ga to thinner 18 or even 22ga metal is a dream. VS butt welding same thickness sheets together. For me anyway. JR


Great points.......it will be 16ga!