For those of you who are reading this issue hot off the presses, it will only be a matter of a couple of weeks before the entire world will be knee-deep into the month of November. If you live in a part of the world where it snows, then there is a good possibility you have been contemplating how you should approach your custom classic truck project. That brings us back to the word deep. You should be thinking about setting up your chassis and beginning on the major changes that you want to make to your cab while it is off the chassis.
Oftentimes purposely overlooked in the rehab stages is the truck's firewall. A good analogy to making repairs to the existing firewall is like imagining what it would be like to fill in all the holes in a block of Swiss cheese. Although it sounds like an overwhelming task, the best way to solve the problem is to cut the unsightly stock tattered firewall out and graft in a new replacement. Not only does this cure the Swiss cheese syndrome, but it will add three more inches of clearance between the engine and firewall, a necessary step for someone interested in dropping in a big-block motor.
The recessed and smoothed firewall insert we used on this Tri-Five Chevy cab is from Direct Sheet Metal of El Cajon, California, and will fit '55-59 Chevy and GMC trucks. The first step, and perhaps the most important part of the entire job, is to brace the inside of the cab where the old firewall will be cut out. Failure to properly connect the area to support it will result in a sprung cab. Once the cab is sprung, it will take a person with major skills to pull it back into shape. From this point on, thanks to the modern miracle of plasma cutters and the remarkable simplicity of a wire-feed welder and its ability to keep the heat zone in check, just about anyone can install a smoothed firewall kit into their truck.
The Direct Sheet Metal kit...
The Direct Sheet Metal kit is a high-quality product manufactured in their 6,000-square-foot Southern California facility by guys who don't even like Chinese food. The kit must be trimmed to fit each individual truck.
Attempting to smooth the stock...
Attempting to smooth the stock firewall shouldn't even be considered as an option. The best method is to cut it out and replace it with a new kit.
It was essential to weld in...
It was essential to weld in braces that would not allow the cab to spring out of shape. This photo was taken after the firewall was cut out, allowing a better view of the braces.
Step two was to mark off with...
Step two was to mark off with a crayon or soapstone where the stock firewall should be cut out with a plasma cutter. Somebody better tell this guy the plasma cutter isn't turned on.
Here's a close-up of where...
Here's a close-up of where we needed to make the plasma cut. Notice how a properly made dolly can make handling the cab easier.
This is where the floorpan...
This is where the floorpan was cut for removal. Notice that they cut around the cab mounts.
After a successful cutting...
After a successful cutting job, the stock firewall lifted out of place with ease. The discarded stock firewall can be recycled as a kitty litter tray.
With the stock firewall cut...
With the stock firewall cut out, the following step was to measure the Direct Sheet Metal firewall and mark where it needed to be trimmed off to fit the firewall opening in the cab.
The excitement starts to mount...
The excitement starts to mount with the first glance at the Tri-Five's new look as the Direct Sheet Metal firewall is held into place.
The top piece was tacked into...
The top piece was tacked into place, followed by inserting the floor panels. Special care was taken not to warp the metal by applying too much heat in a given area. This was done by stitching the parts in with evenly placed tack welds.
This is a good view of how...
This is a good view of how the cab was braced before work was started. It also shows the improved depth created by installing a new smoothed firewall.
Notice the Direct Sheet Metal...
Notice the Direct Sheet Metal firewall extends rearward to the seat riser. As an added bonus, this means rusty floors will be replaced during the process of installing the smoothed and recessed kit.
Here one can see the perimeter...
Here one can see the perimeter of the new floor pieces tack welded in with adjustments to fit made with each new tack weld. Completion is followed by stitching in the unwelded areas with a bead of weld. Again, note that special care must be taken not to overheat the sheetmetal and cause warpage.
Notice the recessed firewall...
Notice the recessed firewall extends almost to the point of aligning with the floorpan opening. This translates into plenty of room for any engine swap imaginable short of a Rolls-Royce Merlin.
With the floor completely...
With the floor completely welded in, the next step was to locate the cab mounts and position the holes with a hole saw.
Once the new holes were drilled...
Once the new holes were drilled for each side, the mounting pockets were welded in. Here's a shot of the completed firewall with the cab back on the chassis and the big-block Chevy engine dropped in. Notice how much room has been added to this once restricted area.