filling in cage holes in the floor
 

I have a few holes from different cages and rollbars in my floorboards. You can fill holes with TIG (or even MIG) by using a different backing metal, but it's pretty thin and I'm afraid to burn through it with the MIG. Right now the holes are covered with foil tape which starts peeling off after a few track days. Any suggestions for patching up the holes (from tiny to 1.5" in diameter)?

Buy a small spool of .023 wire and the right tip. You can weld very thin sheet metal with it. I have been welding holes in my car and it works great.

For the bigger holes I would certainly weld in a patch panel. Just so you dont have a 1.5" blob of filler that you need to grind.

I have similar holes in the firewall to fix. I was thinking of using some sheet metal, sealant and rivets.

I bought a piece of 2'x2' 22 gauge sheet metal and could fill every hole you can think of on the car.

Here is my contribution for the day:

Hole to be filled.
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Take a piece of cardboard and use something heavy to make a dent in it.
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Cut cardboard, trace a piece of sheet metal, and then cut sheet metal.
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I like to build weld up in the middle to give it something to grab onto.
https://www.miataturbo.net/attachmen...ine=1362857009
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You will have to make some adjustments to your piece. It does not have to be perfect.
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Clean area to be welded, weld in place, and clean up with a grinder. I like the paper grinder wheels because of the clean look after grinding.
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I was going to put this in my build thread, but this seems like the perfect thread to put this. Hope it is useful for those not sure how to do this. It is not really hard at all. I am by no means a first class welder.

Again, I highly recommend using .023 wire. It has a tendency to wad up at the wire feed wheels, but you will eventually get the hang of it.

Edit: Pic shows a scotch bright pad. I use it to clean the surface prior to welding, and then use a different pad or grinder to clean the welds. Such as the one two frames up.

let go of the trigger on the mig, hold the nozzle over the weld for a few seconds while the gas in the hose is still flowing to continue shielding the puddle. I think that's why there is a little hole in the center of each weld. ymmv

Thanks for the tip. I will give it a try.

Another option to use is rtv or epoxy to hold down a patch larger than the hole. Kind of like the way the factory did with frame rail access plates. This suggestion is for those afraid of welding or lack access to the equipment.

If you do weld them closed. Make sure you scrape the rubber undercoating off the bottom side near the weld. It catches fire really easy when welding above it. I've forgotten to do that a couple times. No real problem other than having to dirty my welding gloves putting out the flame. :facepalm:

Also, if you are welding thin metal with a MIG you can also use a cheap 100 ft extension cord (plug your MIG into it) - that will drop the voltage a bunch as well.