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Old 10-03-2017, 02:29 PM   #1
gigamanx
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How should I fill firewall holes

Did a little searching and can't seem to find a good answer. I'd like to start filling some of the firewall holes I know I won't need on the cab. I've started marking the ones that can go. What is a good method of getting pieces to fill the holes? For the smaller screw type holes, I tried welding one and just made it bigger by melting the edge of the hole, so that's obviously not the way to do it haha. I don't want to replace the metal with a single sheet since I like the curves and bumps of the original one.

Would love to hear experiences and tips on smoothing things out!
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Old 10-03-2017, 02:49 PM   #2
dsraven
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Re: How should I fill firewall holes

try

https://www.welderseries.com/

on line for some sheet metal plugs for cheap, or shop locally. clean the area well first, then if you grab a cheap stepped drill from harbor freight or whatever you can get a bunch of plugs the same size then drill the cab hole to fit the plug. that way the hole is nice and clean for welding. you can use a copper plate behind so if you have a little burn through it will stay put (weld doesn't stick to the copper). do a series of tacks around the plug, say 2 or 3, then carry on to the next plug because if you weld the whole thing at once you will warp the firewall or wherever you are welding. tack then move on, come back and extend the tack, then move on to allow cooling. soon the plug will be done. you can wipe with a wet rag to help cool and shrink the area so it doesn't warp too bad.
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Old 10-03-2017, 03:16 PM   #3
bowt1ed
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Re: How should I fill firewall holes

I just cut out slightly over-sized sheet metal circles, cleaned surfaces/edges, placed on the inside of firewall (helper to hold tight against), and welded from outside. With that thin a gauge, not too much filler required. As I recall, filled around 45 of them.

Cheers, Jim
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Old 10-03-2017, 03:42 PM   #4
gigamanx
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Re: How should I fill firewall holes

Quote:
Originally Posted by dsraven View Post
try

https://www.welderseries.com/

on line for some sheet metal plugs for cheap, or shop locally. clean the area well first, then if you grab a cheap stepped drill from harbor freight or whatever you can get a bunch of plugs the same size then drill the cab hole to fit the plug. that way the hole is nice and clean for welding. you can use a copper plate behind so if you have a little burn through it will stay put (weld doesn't stick to the copper). do a series of tacks around the plug, say 2 or 3, then carry on to the next plug because if you weld the whole thing at once you will warp the firewall or wherever you are welding. tack then move on, come back and extend the tack, then move on to allow cooling. soon the plug will be done. you can wipe with a wet rag to help cool and shrink the area so it doesn't warp too bad.
See now this is why I asked all you fine smart people... Funny they are called unholes. Here I was thinking I need to cut perfectly shaped pieces to fit in all manner of crazy spots on the firewall. I did not think of my step drill bits.

Quote:
Originally Posted by bowt1ed View Post
I just cut out slightly over-sized sheet metal circles, cleaned surfaces/edges, placed on the inside of firewall (helper to hold tight against), and welded from outside. With that thin a gauge, not too much filler required. As I recall, filled around 45 of them.

Cheers, Jim
That is a ridiculously smooth firewall. Nice job!

https://www.welderseries.com/Unholes-p50202282
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Old 10-03-2017, 04:57 PM   #5
dsraven
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Re: How should I fill firewall holes

if you need a hand to hold the plug, and you have a few extra minutes to spare for fabbing up a quick tool, you can make a magnetic plug holder from a C clamp. just get a cheap steel C clamp and cut the very bottom off, like the bottom of the C part, so you have a vertical portion left there plus the top part of the C with the screw down part still intact. now drill up into the vertical section and run some threads into it. find a round magnet that sticks well and has a hole in the middle and is also smaller in diameter than the distance over to the threaded part of the C clamp. some dollar stores will have everything you need, the clamp and the magnet. the magnets sometimes are sold with a hook on them that is bolted on through a hole in the middle, perfect. toss the hook in the junk bin. bolt the magnet onto the bottom of the C clamp so it will hold the clamp vertical. now you can magnet the clamp onto the back side of the firewall and then screw the threaded part down so it sits level with the sheet metal and holds the plug in place. the clamp comes in handy for other stuff too.

or just use a magnet to hold the plug but then the magnetics will deform the mig welder and cause spatter. of you are torch welding then it won't matter, haha.

I think I spend more time making tools than I do working on the truck. dough head alert.
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Old 10-03-2017, 05:41 PM   #6
Dan in Pasadena
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Re: How should I fill firewall holes

Quote:
Originally Posted by bowt1ed View Post
I just cut out slightly over-sized sheet metal circles, cleaned surfaces/edges, placed on the inside of firewall (helper to hold tight against), and welded from outside. With that thin a gauge, not too much filler required. As I recall, filled around 45 of them.

Cheers, Jim
^^^This^^^ is what was done with my firewall too. We stopped counting at 50 holes!

Came out good and I had wondered if it would repair decently.
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Old 10-03-2017, 06:29 PM   #7
fourspeedwagon
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Re: How should I fill firewall holes

Well, Yesterday I would’ve said to do exactly what dsraven said.. but now I’m wondering if Jim and Dan’s method isn’t the way to go.
I may be picking up a new-to-me ‘51, and noticed it has quite the shotgun scatter of holes. Only thing different I was thinking was to zap a mig wire to it as a handle so I wouldn’t need magnets and cut off C clamps etc.
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Old 10-03-2017, 08:31 PM   #8
dsraven
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Re: How should I fill firewall holes

this is what I did. 16ga. totally flat now.
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Old 10-03-2017, 08:37 PM   #9
dsraven
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Re: How should I fill firewall holes

the rest of the story. cut it out so it will fit over the envoy donor
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Old 10-03-2017, 08:50 PM   #10
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Re: How should I fill firewall holes

the rest of the story. it became a donor for the envoy frame swap. really not that much more work to replace the whole thing though compared to plugging and finishing all the holes. especially if the floor is also rotten. the point is not my swap, it is the work involved to just replace the whole thing. wasn't that much really once I figured out how big to make the recess. need to remember to leave room for the gas pedal though. some guys just do a square recess so that would be easier.
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Old 10-03-2017, 09:29 PM   #11
greg_h
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Re: How should I fill firewall holes

The advice I was given was to find a flat washer that fit the hole, weld it in, and the weld up the small hole in the washer.
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Old 10-03-2017, 11:10 PM   #12
fourspeedwagon
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Re: How should I fill firewall holes

Wow! Dsraven that extended cab rig is amazing.
Now I’m off to see if there’s a build thread on that. Awesome truck
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Old 10-03-2017, 11:47 PM   #13
Dan in Pasadena
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Re: How should I fill firewall holes

I suppose someone should mention one other alternative:

Aftermarket suppliers use to make a fiberglas sheet that covered the stock firewall and it had a recess in the center too. It simply bolted in behind the hood hinges and the top was shaped exactly to fit under/up against the factory pinch weld.

I don't see it offered on the one site I knew used to sell them: No Limit Engineering

CORRECTION: Gibbons lists a part number CH523 Smooth Firewall Cover. Maybe it's this part. No pics on their site.
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Last edited by Dan in Pasadena; 10-04-2017 at 12:38 AM.
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Old 10-04-2017, 12:02 AM   #14
iowaboynca
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Re: How should I fill firewall holes

With all the craftsmanship, i'm a bit embarrassed to say I used various sizes of fender washers. Used either screws or small magnets to hold on to firewall to tack weld.

For the big holes cut out filler out of 18g sheet metal and tack/stitch welded.

You can see the results below.
http://67-72chevytrucks.com/vboard/s...3&postcount=97
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Old 10-04-2017, 06:57 AM   #15
Dave0
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Re: How should I fill firewall holes

I cut all mine the same size with a throatless shear and a disc grinder.
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Old 10-04-2017, 07:49 AM   #16
hogfarm
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Re: How should I fill firewall holes

I went to the local machine shop and they gave me a coffee can full of the drops from there punch press,all different sizes
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Old 10-04-2017, 04:11 PM   #17
MARTINSR
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Re: How should I fill firewall holes

This is only for the small holes up to a half inch but a great trick I learned years ago from a Ron Covell basic metal working VHS tape, yes a VHS tape, that's how long ago we are talking. It was shown in the first few minutes of the video and I remember stopping it and saying to my wife, "I could take this tape out and throw it in the garbage right now, that one trick was worth what I paid for it and more!"

What you use is the metal you punch out of a hole using a Roper Whitney punch like this, the XX.



Or this one, but the holes are much smaller, the "jr."



I have to say, if you are doing a fair amount of fab work, these tools are a MUST HAVE. But in this case, you are just punching a hole in a piece of scrap metal. The piece of metal you punch out has a big dent in the middle, the piece is stretched up a little bit. You then take a hole you want to fill and you open it up using a variable bit or step bit until the hole barely fits the piece you punched out of the scrap metal. You put that piece in the hole and then with a dolly on the back you tape the piece with a flat body hammer and the piece gets larger because of the dent sticking up is now pressing into that piece and spreading it. The piece now fills the hole and stays there! A tiny bead around the edge and wham, no more hole.

Oh, and that punch, you can get dies to punch square holes and oblong holes and many others, I use them all the time! Awesome tools to have in your box.

Brian
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Old 10-04-2017, 04:13 PM   #18
gigamanx
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Re: How should I fill firewall holes

Quote:
Originally Posted by bowt1ed
I just cut out slightly over-sized sheet metal circles
How did you cut them out?

So far, various sized washers or just going to the local metal shop for some scraps seems to be the way to go. I like all these genius little tools made from things laying around. I'm new to welding, so my mind doesn't wrap around the idea that I can build all manner of little dohickies for the garage.
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Old 10-04-2017, 04:14 PM   #19
gigamanx
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Re: How should I fill firewall holes

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Originally Posted by hogfarm View Post
I went to the local machine shop and they gave me a coffee can full of the drops from there punch press,all different sizes
That's a great idea!
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Old 10-04-2017, 05:48 PM   #20
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Re: How should I fill firewall holes

for any hole .5'' or under i just welded them closed while holding a piece of brass on the back side
weld won't stick to the brass and the brass acts as a heat sink to prevent weld blow out
a piece of flattened copper pipe works well too, it just gets really hot quickly

for bigger holes i just welded scrap 16 ga squares, carpet covers them well

i shaved the firewall flange while i was at it
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Old 10-05-2017, 04:35 AM   #21
Jesse Z
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Re: How should I fill firewall holes

Someone prior owner filled all the holes in my firewall, but I can't figure out how. There appear to be plugs inserted in every hole that fit so perfectly without ever being welded that it literally requires a magnifying glass to see them - primer would no doubt cover them completely. Anyone know how this was done?
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Old 10-05-2017, 04:51 AM   #22
bennylava
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Re: How should I fill firewall holes

Quote:
Originally Posted by bowt1ed View Post
As I recall, I filled around 45 of them.

I can only imagine the massive cost of having a shop do that. Any idea what it would cost?
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Old 10-05-2017, 07:16 AM   #23
Dave0
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Re: How should I fill firewall holes

I filled over 65 in mine and almost every one was a factory hole!
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Old 10-05-2017, 11:49 AM   #24
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Re: How should I fill firewall holes

I'd recommend one of these.

http://www.eastwood.com/magnetic-hol...8aAkpwEALw_wcB
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Old 10-05-2017, 12:05 PM   #25
Dan in Pasadena
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Re: How should I fill firewall holes

Quote:
Originally Posted by iowaboynca View Post
With all the craftsmanship, i'm a bit embarrassed...
Psh....NO reason to be embarassed. You did the work and if you're pleased with it that's all that matters. Be proud!
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