What gauge sheet metal thickness for firewall??

[BlackGMC]

Hello, I am going to replace a large portion of my firewall and I was wanting to know what gauge sheet metal to go with? The reason I am replacing it is to smooth it out, the factory firewall has all sorts of holes for AC and Heater and wiring harness. So what would yall recomend? OH and this is for a 1970 Mustang coupe.

Thanks in advance

Corey

[parsonsj]

I wouldn't go thinner than 18g, and would recommend 16g.

Mustangs are uni-body vehicles and the firewall is an important structural element.

jp

[BlackGMC]

I wouldn't go thinner than 18g, and would recommend 16g.

Mustangs are uni-body vehicles and the firewall is an important structural element.

jp

Thanks, sounds like I will go with 16g. I might add a little reenforcement to the backside. I am planning on keeping is smooth and not rolling any beads, do yall think that would be OK. I never really knew if the rolled beads helped?

[parsonsj]

You should consider the use of beads or backing structural members to reduce flex (called drumming) in large flat sections of sheetmetal. Here's a photo of my floor, where I used both techniques.

http://www.iimuchfabrication.com/Floor/photos/full%20floor%20005.html

jp

[BlackGMC]

You should consider the use of beads or backing structural members to reduce flex (called drumming) in large flat sections of sheetmetal. Here's a photo of my floor, where I used both techniques.

http://www.iimuchfabrication.com/Floor/photos/full%20floor%20005.html

jp

Well I don't have the tool to make beads, so could I get away with some round or flat bar welded to the back side of the flat sheet? Or maybe I might just look into a bead roller.

[parsonsj]

Did you look at the link? See those beads? The tool to make those cost me $79 at Harbor Freight.

jp

[BlackGMC]

Did you look at the link? See those beads? The tool to make those cost me $79 at Harbor Freight.

jp

I did look at the link, and all I can say is wow!! Looks great. Harbor Freight, huh, I might just have to go over there after work. I appreciate all you responses, you have been a great help.

[parsonsj]

Good luck, let us know how it goes.

jp

[80proZ]

have fun bead rolling 16ga.Although i agree with parsonsj about the firewall being a structural peice, i would use 20ga.It should be plenty strong enough when beaded and welded in.

[CDJr]

Ya, I dont know if youll be able to roll good beads in 16ga with a HF roller, I could be wrong though. The original firewall was probably 20-22ga. The reason its so rigid is because of the bends in it. If you want it smoothe, Id suggest leaving it flat and welding in braces on the backside, maybe small angle iron or something.

[novanutcase]

You should consider the use of beads or backing structural members to reduce flex (called drumming) in large flat sections of sheetmetal. Here's a photo of my floor, where I used both techniques.

http://www.iimuchfabrication.com/Floor/photos/full%20floor%20005.html

jp

Dammit John! Every time I think I'm getting somewhere with my car I see yours!:)

[parsonsj]

Every time I think I'm getting somewhere with my car I see yours!Yeah, those floors took me months to make. To finish them, I moved all the daily driver cars out of the garage, moved all my sheetmetal tools into the garage, and worked around the clock for weeks. What a job!


i would use 20ga.It should be plenty strong enough when beaded and welded in.That's probably true if beaded or backed with structural reinforcement. The problem is that can be difficult on a firewall. Using 18g or 16g gives you some forgiveness when welding and with strength. Firewalls are important structurally with a unibody car. I wouldn't try to save too much weight there. YMMV.

jp

[Bigblue73]

If you don't want to buy the tooling I would recommend going to a large commercial HVAC fabrication shop in your area. If you provide them with a card board template. They can roll the beads about the perimeter and match the overall size relatively easy. If you don't have any place in your are, PM me. I work for a fabrication house in Missouri.

Mr. Parsons - My hats is off to you...you have excellent fabrication skills! Nicely done.

[CDJr]

Boy aint that the truth! He did/is doing some fine metal work there. Looks great JP!

[BlackGMC]

Thanks for all the input guys. I am still a little ways away from cutting the firewall. I am still in the process of leveling the body/frame and stripping all the 30 years of crud off the car. Then I am going to do the floors and subframes, then the firewall. I will probably end up using either 16 or 18 gauge with some kind of backing material welded to it. But I am going to try to roll some beads with the HF roller.

On a side not I noticed that Summit had a bead roller for sale, it is a little bit more expensive but it says it only rolls 20 gauge.

[nbecker]

hey john did you buy the dies and build a beadroller? any info would help. thanks in advance

[parsonsj]

I bought the whole thing (bead roller and dies) for $79 from Harbor Freight. It works fine, but is definitely a two man tool.

Once I even got the cute wife down the street to wind my crank while I fed sheet metal. :)

jp