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Body Repairs: Firewall Installation

Once the rocker panels were replaced and the cowl boxes repaired, the firewall could be installed.

Since I was planning on installing a small block Chevy, I ordered a Bitchin' Products firewall with a 3-inch setback. A trial fit of the firewall indicated that it would only require some minor trimming at the bottom.

Prior to installation, I used a hammer and dolly to straighten out the cowl and removed some light rust from the inside. I also cleaned the new firewall with PPG DX 579 and then primed it with DP 40.

The key firewall installation points are:

  • Begin clamping the firewall to the cowl at the top center
  • Don't pull down the front of the cowl to meet the firewall
  • The firewall has to be level, square and clamped securely to the cowl
  • Begin the welding with tacks at the lower corners
  • Before final welding, check alignment
  • Final welding involves filling all 80 spot weld holes with rosette welds
  • When welding, skip around to minimize excessive heat.
  • Apply seam sealer where the cowl meets the firewall (on the inside)



Bitchin' Products provides very complete firewall removal and installation instructions with lots of pictures. Also, there are several firewall installation articles in previous issues of Street Rodder and Street Rod Builder.


Bitchin' Products:

Direct Sheet Metal:

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