Tri Five Tech Talk

Darryl Nance Mar 21, 2003 0 Comment(s)

Last month I talked about a variety of issues related to engine compartments. One was smoothing out the firewall. Tri-Fives were built with functional, but less than attractive, firewalls. Let me guide you through the process of smoothing it out. The cost of the smooth firewall kit is less than $300. There's one kit for '55-56 Chevys and one for '57s. The kits come in two sections and are ready to weld on. They have a clean bead rolled into the upper portion of the panels.

Smoothing out the firewall involves some work, and you may wish to seek help from a professional. First, you'll need to remove the front bumper, hood, hood hinges, and front end. The front end, including the splash pan, grille, fenders, air ducts, etc., can be removed as a unit. You will also need to remove or disconnect all heater or A/C assemblies, air ducts, fender braces, wiring, etc. Next remove the core support bolts at the frame, the lower fender bolts at the cowl, the upper fender bolts at the cowl, and the inner fender braces. To lighten the front end, remove the radiator. The installation of the firewall panel kit is easier if the engine is out.

You'll need three strong friends to help you remove the front end. Mask off the cowl and doors, so they don't get scratched. One person will need to lift up at the core support. There needs to be one person on each side of the fenders. While lifting out on the bottom of the fender, start lifting upward to clear the cowl. Both '55 and '56 Chevys had their batteries mounted on the firewall. It is simple to relocate the battery to the trunk, which will be necessary to clean up the firewall.

Installing the firewall panels involves cutting, welding, and grinding. To prevent fire, remove the pad and any insulation on the inside of the firewall. It's also best to disassemble the dash to prevent damage. Interior items should be removed and or protected from grinding and welding.

You don't need to remove the stock firewall to install the smooth panels, but you do need to modify it. First, remove the factory vertical ribs. Slice into them and flatten them, or simply cut them out. Next, shorten the factory dash braces down to the bottom of the firewall. You may wish to weld them to the firewall when shortened. You can make boxing plates to enclose the factory forward mount for a clean look. Remove all caulking or any other high spots.

Owners of '57s will need to cut off the raised area around the heater box. Once this is done, you can place the panels over the existing firewall to check for clearances. Use the factory hood hinge holes for alignment. Trim or adjust as necessary until you have the desired fit. Prime and/or paint the firewall and the backside of the firewall panel kit to prevent rusting. Along the edge you can use weld-through primer that allows for penetration when welding.

With the panels in place check the fit and clearance on the inside of the firewall. If everything is correct, begin welding the panels in place. Make sure they are solid and flat against the firewall so you don't have an oilcan problem. Once the panels are welded, you can grind the edge and perform any final metalwork and prep the area for paint.

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Here is what most unrestored Tri-5 look likes upon purchase. With everything removed from the firewall you can really see how bad it is.

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The proper way to smooth your wall is by first removing the two chassis from the surface of the firewall.

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You are going to cut these braces at the bottom of the firewall and weld just below the flat of the firewall.

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Here is one in the process of being completed, see how the brace is cut on the bottom of the wall. Then this smooth plate is welded into place. You can see around the edge were it is welded and now it is being smoothed.

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Here is another that is in progress, kind of. You can now more noticeably see the plate that is installed. This firewall is still good; it just got some surface rust from having to be put on hold.

The results are a major improvement over the factory firewall. If you plan on installing the Raingear (or similar) wiper system, you can fill the old wiper center drum hole, as you won't need it. You may also want to hide your wiring when you smooth the firewall. If so, you can fill the hole that the starter/ignition harness goes through. These wires can be relocated lower on the firewall behind the transmission where they are hidden. The installation of the firewall panel kit usually takes 8-12 hours if the front end is off and the motor is out of the way.

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