Fire wall 101
This is one of the easiest ways to smooth your fire wall for in cab AC. EXTD56 will need to tell us what brand it is. They give you a plate that is designed to mount on the fire wall to cover up all the holes and provide mounting for the heater/cool box. All I did was took that plate and recessed it into the fire wall for a cleaner look.
Here is the process.
First remove your heater and any thing inside the cab that WILL burn.
Take your fire wall plate and remove the foam from the back side of it and clean all edges that will be getting welded.
Clamp it to the fire wall and use a sharp scribe to mark the out side of it.
Now just cut right up to your mark. The cleaner your cut is the better because you do not want much if any of a gap since that will take more welding (and we know welding= heat and that = warp city) and grinding.
Once it fits good start tacking it in place making sure it is flush before welding. If it is off a bit just take your hammer and dolly (no not your kids Dolly) and work the edge to get it straite. Once you are tacked about every inch you are ready to start welding it up. Skip about 4 tack welds each time and work your way back around. I also made a plate for the fan hole and started it the same way. Once I make one turn around skipping welds I will go to the next plate giving the first plate time to cool. Repeat untill you are all welded up. Then start grinding, I like to use a 4" .040 cut off wheel for weld grinding and then I switch to an air grinder with 3" disks (50g, 80g, 120g) and you should be ready for some epoxy primer and fill primer.
Kevin
LFD Inc.