While waiting for a few suspension components to show up so we can get Ramrodder up on its wheels, we turned our attention to what firewall modifications would be necessary to stuff a blown early Hemi in the space once occupied by a flathead six.
Ironically both engines are about the same length, around 32 inches from the farthest point forward (the fan on the six and the blower pulleys on the Hemi) to the bellhousing surfaces. And while that would seem to indicate that space wouldn't be a problem for our V-8 transplant, like many cars of the era that were equipped with six cylinders, the firewall has an indentation in the center to accommodate an inline engine. Further complicating fitting many early Mopars with a V-8 is the shape of the firewall above the toe boards adjacent to the indentation--it kicks forward on both sides just about where the heads want to be.
After concluding the firewall needed some modification, it was decided that the easiest method was to simply cut out the protruding portions and weld in some flat sheetmetal, but then Leroi "Tex" Smith stopped by the shop to see what we were up to. A dyed-in-the-wool Mopar fan, old school hot rodder, and talented metalworker (not to mention co-founder of this very magazine) Tex suggested another approach. Basically his idea was to cut those protruding sections loose, straighten them, and reattach them to the toe boards and the center section. By doing so, all the ribs, lumps, and bumps of the original would be retained for a factory look, and we'd have the increase in space we were after.
Although we're working with a blown Hemi, just about any V-8 swap could benefit from the same procedure--here's how to do it.
With the stock steering and...
With the stock steering and suspension removed and the Fatman Fabrications stubs in place, we decided to modify the firewall to make more room for our blown Hemi.
Tex Smith laid out where the...
Tex Smith laid out where the cuts need to be made to push the protruding portions of the firewall back and make the firewall flat.
The vertical cuts were started...
The vertical cuts were started with an abrasive cutoff wheel--the horizontal line at the top indicates where the firewall will be bent to the rear.
With the cuts started, a reciprocating...
With the cuts started, a reciprocating saw was used to continue them to seam where the firewall joins the toe board.
After making a horizontal...
After making a horizontal cut at the toe board joint, the severed firewall was straightened by hand. After some trimming it was reattached to the toe board with some tack welds. Notice the resulting gap to the left; an indication of how much engine compartment length will be gained.
Once the firewall section...
Once the firewall section was straightened, the area between it and the factory indentation would have to be reshaped.
The section to the right of...
The section to the right of the now straight firewall was cut horizontally and a second vertical cut was made so it could be hammered flat. Some trimming was required to make it fit. Note how the lower section now overlaps the straightened portion--it was trimmed before hammering it into position.
On the driver side the procedure...
On the driver side the procedure was the same--the protruding portion was straightened--but the removable floorboard on this side of the car is rotted and will have to be replaced.
The indented area was again...
The indented area was again split horizontally, hammered flat and trimmed to fit before being tack welded in place. The bottom flange indicates the firewall's original shape. It was cut and reshaped as well.