How to Make a CCKW Firewall Pad for Under $30

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Sergeant Major of the Gee
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Location: SE MI

How to Make a CCKW Firewall Pad for Under $30

Post by mudflap » Sat Jan 25, 2020 9:52 pm

Carpenter-contractor Tom Silva, from the home improvement show “This Old House”, once said that the four most expensive words in the homeowner’s vocabulary are: “While I’m at it”. I think this can frequently apply to CCKWs or other HMVs as well. There have been many times when my original repair estimates were seriously derailed, after I decided to make an additional repair(s) since I was “already in there any way”.

Such is the story in this post – although I think for once I actually got off pretty cheap. Last summer, I had the engine out of the truck, and since many of the lines, hoses & wires were already disconnected, I figured it would be a good time to replace the deteriorating firewall pad.

The firewall pad on my truck was literally falling apart. I think that this is especially noticeable in the open cab, since the pad is pretty much at eye level to anyone standing on the ground looking into the truck. In fairness to the manufacturer, it is only made of cardboard. I’m sure lasting 75 years was never even dreamed of as a requirement by the original engineers.

Firewall Pad 01 Med.jpg
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The first thing to do was to locate a suitable material for the replacement. This proved difficult at first, since I kept searching for “cardboard”. I finally learned that cardboard tends to be the multi-layer corrugated stuff used for boxes, which is not what I needed. I realized, that what I should be looking for was chipboard, which is much like the material found in the covers of hard-cover books.

The stuff used in the truck appeared to be 1/8” thick, with a corrugated cardboard backing. The only chipboard I could find locally, in a length and width that would work, was 1/16”, so I figured I could maybe just take two pieces, bend them, and glue them together to get the 1/8” thickness. This actually worked out well, since glue line stiffened the pad and helped keep the bends at the correct angle.

I bought three sheets for just under $4 a sheet. I used one as an initial pattern. I trace the holes and creases from the original on to the pattern, then installed it in the truck, and made any necessary adjustments.

Firewall Pad 03 med.jpg
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Next, the first sheet was trimmed based on the pattern. I creased the chipboard with a piece of plastic on the bend lines. I found also, that slightly wetting the bend line helps to keep the surface from tearing during the bend. Once the first piece was bent, a second piece was bent and glued to the first piece using contact cement.

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I found some split rivets from McMaster-Carr, that were pretty close to the originals. The only difference is that the heads were rounded, however a couple of passes with a file and they were flat like the originals. Holes were punched in the chipboard, the flap interface was glued with contact cement, and the rivets were installed using a washer to help keep them from tearing through the chipboard.

Firewall Pad 06 med.jpg
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Speaking of holes, there are a number of different sized and shaped holes in the pad. I did not have any of the punches required for these sizes, so I cobbled some up from scraps of tubing, electrical conduit and pipe that I had lying around. To make a punch, you just hit the end with a countersink, then finish the edge with some 600 grit sandpaper. Stainless tubing works best, as it seems to hold its edge better than plain steel tubing. I have used this technique before for punching holes in gaskets, or other thin soft material. Just back up what you are punching with a scrap piece of chipboard, or soft wood and hit the punch with a hammer. It obviously would not work in a production setting, but for short run jobs like this it works fine. For the rectangular holes for the retainers, just squish a round tube in a vice.

Firewall Pad 07 med.jpg
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In order to help reinforce the holes and perimeter edges, a light coat of epoxy was brushed on. It was also applied to any of the bends to help strengthen them.

Firewall Pad 08 med.jpg
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To be continued...….
Last edited by mudflap on Sat Jan 25, 2020 10:15 pm, edited 3 times in total.

Sergeant Major of the Gee
Sergeant Major of the Gee
Posts: 352
Joined: Sat Dec 28, 2013 1:07 pm
Location: SE MI

Re: How to Make a CCKW Firewall Pad for Under $30

Post by mudflap » Sat Jan 25, 2020 10:05 pm

Part II

Once cured, the epoxy was sanded and feathered, and a coat of primer was sprayed on to both sides. After a little more sanding, several coats of OD were applied.

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As mentioned, the original design uses a backing of corrugated cardboard. Not being too crazy about using this, I found some ¼” sound deadening material at a craft store. (Not that I'm really going for db reduction here - it is after all, an open cab - but it does help the pad sit in place better.) I cut it to size, punched holes in it, and glued it to the back of the pad using contact cement. The holes in the pad were also brushed with epoxy to keep the from absorbing any water that might weep into thru the holes in the firewall.

Firewall Pad 11 med.jpg
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Final Cost:
$11 Chipboard
$ 1 Rivets
$10 Insulation
$ 6 Misc. glue, paint
$27 Total

After install, I think it looks pretty good. Definitely a huge improvement over the old and busted original.

Firewall Pad 12 med.jpg
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I did not punch all of the holes found in the original (like the ones for the heater). If I ever install some accessory that needs the extra holes, I figure that I can just punch them – “while I’m at it”.

Best Regards...

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Location: Western North Carolina

Re: How to Make a CCKW Firewall Pad for Under $30

Post by forestry4evr » Sun Jan 26, 2020 3:06 am

Great work! Funny how things go "while your at it", but I think you did a fantastic job. I particularly like your idea of making the oblong hole cutter, simple but quite ingenious. Thanks for sharing.
1941 G4112 Chevrolet with Hercules dump bed

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