The Stovebolt Site Forums The Shop Area Paint and Body Shop Plugging Firewall Holes

On my 1953 GMC there are numerous extra holes in the firewall that are not being used by wires or cables. What is the best way to cover or plug these holes? Are there rubber plugs of various sizes available?

Steele Rubber Products and Restoration Specialties & Supply sell plugs.

Thanks for the information. They have rubber or metal plugs available.

You may also consider using Loctite Black RTV Silicone. Cecil.......

I'd just fill 'em with silicone, but that might not look all that pretty.

Most hardware stores and electrical supply places sell nice plastic grommets and plugs that are designed to be used with electrical boxes.. if you want it to look pretty, just drill your extra holes out to 3/4" and pop in the plugs.

If in the future you need to use one of the holes, just pop out the plug, pop in a gromet, and use the nice hole.

They're paintable, removable, and look nice.. but won't do any good for large 1" holes.

Usually the street rod crowd will weld them up, smooth the firewall and paint - it makes everything look nice. Usually they route all the existing wires through some kind of single bulkhead connector - which also makes removing and replacing the motor easier.

Plugging these holes will also definitely make a big improvement in the amount of noise in the cab.

If you have a really good hardware store near you....the kind that has all of the little plastic cases with slide-out drawers and all sorts of little pieces and parts...then look for metal (usually chrome) or black plastic plugs and grommets. They're so cheap this way, that you can usually buy a bunch and not worry about size, and go home and try them all. I like the black plastic ones, because you can paint then to match your firewall (if you insert them from that side), or you can dab some silicon on them to keep them in place and never come out. Of course, if you're doing major work to the body, just mark all the superflous ones, and weld them closed.

Welded up most of my firewall holes this past summer. Used different hole saw sizes to cut plugs to fit the many size holes. Held a piece of copper behind the hole while my son welded from outside the cab. By using the plugs and sanding most of the weld off, we didn't have to use much body filler.

I welded most of mine up this summer too. Hey coach, is there something particular to using copper? I used one of those fireproof cloth type things I had from a plumbing job to keep from burning the house down when sweating on joints in the wall. Worked great too.

Dennis, The weld won't stick to the copper. I just smashed a piece of pipe I had laying around.I held it behind the hole with an extra long pair of needle nose pliers, while my son welded the plug in the hole.

Good to know. Thanks coach.

I was looking at my firewall just the other day and thinking about closing up numerous unused holes.

I decided to just use knock-outs from electrical boxes. A little silicone around the edges or a little JB Weld to hold them in place. My thought was to cover the existing hole, not to fill the hole per se. With silicone use they could easily be taken back off if needed.

I figured when painted over they would look like they were supposed to be there.

Another idea is to just put machine screws or bolts with appropriate sized washers with the nut on the inside. After filling the holes I didn't like the mount for the steering column brace. I got some carriage style bolts for that with the nuts on the inside. Looks more like a rivit and a finished to me.

I just yanked my leaky heater last weekend. For a temporary seal I put on that furnace tape, (sticky on one side, foil on the outside). However I will clearly reuse these holes so I didn't want something very permanent.