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Bolting Things To Firewall

Old 02-12-2019, 12:34 PM
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Default Bolting Things To Firewall

Im looking for clean looking ideas for bolting things to the firewall. I currently have my PCM, TCU, and truck gas pedal bolted to the firewall on the Chevelle and I dont like screws protruding into the firewall area.. Im working on cleaning up the firewall and welding in unnecessary holes and things and I would like to find a better, cleaner way to do this.

I have Rivnuts but they protrude quite a bit when in place. I suppose I could find other places to bolt the PCM/TCU as well, but I would like to get other ideas first.

Any suggestions?

Thank you
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Old 02-12-2019, 01:04 PM
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Weld nuts on the inside of the firewall to hold everything?
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Old 02-12-2019, 05:15 PM
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I hate sheet metal screws sticking thru sheet metal. I assume the computer and such are on the engine compartment side of the fire wall. If so I weld pieces of 3/16" material to the inside of the firewall and drill and tap mounting holes for what ever is needed.
If the computer and such are mounted inside the fire wall I would make brackets with drilled and tapped holes to mount the computer. Then making bends in the bracket to space it away from the fire wall and then weld the bracket to the fire wall. The spacing away from the fire wall gives a little room for the computer mounting bolts to protrude thru the bracket.
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Old 02-12-2019, 05:25 PM
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Never used these myself, but know people that have. Will require welding them to the firewall. If you have a lathe, these can be made pretty easily.

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Old 02-12-2019, 09:08 PM
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Ever looked into a stud welder? Basically welds a threaded stud onto the metal then you can fasten whatever with a nut.
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Old 02-13-2019, 07:06 AM
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I have pondered the idea of panel bond and elevator bolts. Would probably only work with light weight things, tach box, ecu, aux fuse panel. This thought came after I had already smoothed my firewall.
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Old 02-13-2019, 08:25 AM
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When I build a street rod I weld a strip of angle iron across the inside of the firewall. Holes are drilled in the angle iron about every two inches to hang stuff on and for a cable run. Result is no nuts and bolts thru the firewall at all, neat cable run and a host of TAC, Fuse panel, A/C and whatever mounted to the angle iron.
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Old 02-13-2019, 08:58 AM
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I attached my gas pedal with bolts/nuts -- and put the bolt through from the engine side/nut on the inside. So all you see is the bolt head. Used a couple of plates to block off firewall holes I didn't use. I used a small bit of silicone to seal, placed the plate INSIDE the passenger compartment and then riveted the plate in place from the engine side. All this before the engine was dropped in for the final time.

To fill small holes in firewall and fender liners - I screwed an oversized sheet metal screw into the hole, used Dremel to cut off the rest of the screw head, tack welded it so it wouldn't come loose (although, because oversize, they were danged tight) and ground down/smoothed/filled/sanded --- before painting. MUCH quicker than welding them completely shut. And put MUCH less heat into the flat panels to avoid warpage.
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Old 02-14-2019, 02:33 PM
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I have looked into a stud welder. I will definitely consider using one.

Those Fab Bosses look pretty good too

Ill use the sheet metal screw trick when Im filling in those holes for sure.

Thanks for all of the great tips everyone! Very much appreciated!
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