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I wanted to fill some of the holes in my firewall that won't be needed anymore because I'm planning on installing a v6 with new wiring kit. I'm not sure if I can just weld a plate behind and fill the holes from the front. Or will I need to make plugs to match the holes and butt weld them in?
Anyone done this yet?

we just cut little square pieces of sheet metal, i was inside the cab pushing against them with a screwdriver my buddy was outside tacking them. welded them up,ground them a little filler and called it good.worked for me...................dave

If you know a electrician ask them to save some knockouts. Throw a magnet on the back and weld from the front. As Dave said grind ,fill, prime and paint. Good luck and have fun
Dan

Call around to sheetmetal shops and see if they have a Rotex punch. If you find one ask them to punch out some slugs to the size you need. If you have a step drill you can bore out the holes to a larger, more common size.

Yes, there are other punches that can punch out slugs but a Rotex is simple and fast with no setup required. Should be able to get all you need for a pittance. You'll just have to hammer them flat, the will come out bent. The punch is used to get a clean hole, not produce a clean slug.

I just don't like the idea of you scabbing a lot of square pieces of metal to the back of your firewall when you can make a nice, clean job out of it.

What happened to holding a copper spoon behind the hole and just welding it up? I remember reading quite a bit about doing this and for the most part it seems the way to go????

that'd be the deal for screw size holes Alvin, but for the heater hose/ wire grommet size, some backing helps

Bill

Thanks
Dave,4t6,czechman,Achipmunk,& Red58. I have found that everyones advise is very usable. Smaller holes were welded with a copper backup spoon, had some old electrical boxes some of the knockouts were ok to use,also did find a shop to make some slugs that fit real nice using the Rotex, when I told the guy why I needed them he said it would cost more to do the paperwork so he said don't worry about its on me! 1 hole was sort of long and rounded at the top so a backup plate was used.

Good to hear... I've always felt that no matter how menial or insignificant the job you should always try to do the best you can. It may be something that no one will ever see but you'll know it's there.

I used a combination of plugs I made with tin snips for the larger holes, a spoon for the medium sized holes (both welded with a mig welder) and then leaded the small holes. The results are well worth the effort.
Before: http://picasaweb.google.com/ChrisAurit/BeforeAndAfter#5224669436113643378
After: http://picasaweb.google.com/ChrisAurit/BeforeAndAfter#5242108253679131842

I just welded in circles until the hole closed up.... then used the grinder to make it flat.

as above, that's not a very good way to close up the larger holes tho; but it's possible.

another way it to put in a bolt that fits the hole, weld it, then grind off the head.

i used wahsers i used a step drill to enlarge the holes to fit the washers and when they were welded in i used a coper bar to fill the small hole turned out good