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Richard Ohran · 07-01-2001, 05:15 PM

I'm cleaning up the rust that was underneath a vinyl top on 70 firebird. There are quite a few place where there are small holes rusted all the way through. Since this goes into the passenger compartment where there is very little moisture, am I safe in just using bondo to fill them? What about knocking them in a bit and using my spotweld panel puller thing (can't remember what that gun is called) to weld on a wire, and then grind it off? Or, I guess now is the time to practice migwelding on sheet metal.

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Richard/Vegas

If a man makes a statement in a forest, and there are no women present to hear him, is he still wrong?

Richard Ohran · 07-01-2001, 05:15 PM

I'm cleaning up the rust that was underneath a vinyl top on 70 firebird. There are quite a few place where there are small holes rusted all the way through. Since this goes into the passenger compartment where there is very little moisture, am I safe in just using bondo to fill them? What about knocking them in a bit and using my spotweld panel puller thing (can't remember what that gun is called) to weld on a wire, and then grind it off? Or, I guess now is the time to practice migwelding on sheet metal.

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Richard/Vegas

If a man makes a statement in a forest, and there are no women present to hear him, is he still wrong?

Michael G · 07-01-2001, 08:59 PM

Richard, Attempting to mig weld rust holes may not be a good idea.
I'd take the roof down to bare metal. At the rusted area use a 25 grit sanding disk which will prep the area for the filler. After sanding, slightly dimple all the holes with a clean center punch and apply a thin layer of premium light weight filler. Sand and fill, sand and fill, sand and fill, till it's smooth. Prime and paint.
When you got the outside done, seal the inside with por 15 to keep any moisture from attacking the area from the inside.
Who knows, you may bring the car east some day.
That's what I would do.
If you decide to go the mig route, keep in mind that it doesn't take much heat to warp a large area like a roof. Enjoy.

Richard Ohran · 07-01-2001, 10:24 PM

Thanks for your advice, Mike... I had pretty much come to the same conclusion. Only problem is I can't get to the inside surface to put on the Por-15. There are additional sheet metal pieces spot welded for strength. But, since it's pretty dry out here, and the back side will be inside the car, the moisture problems should be minimal. If it bubbles, I'll repaint it. The car is a non-metallic orange color so it will be fairly easy to match. As you say, it's pretty tough to mig well a big surface like a roof without warping it. It's pretty straight right now, and I don't want to screw that up.

Richard/Vegas

jim darlington · 07-02-2001, 06:07 AM

You better stock up on the paint , it will bubble . Do it right ....weld in new plates .

djokk · 07-02-2001, 09:03 PM

If you use a filler make sure you use the type that does not absorb water. It will last much longer.

Ken K · 07-02-2001, 11:52 PM

Are you going to reinstall the vinyl top? If so paint the top of your car with poly urathane, water will not penitrate it. If you hit the pin holes with a wire feed welder they will not be pinholes any more, the welder will burn all the bad metal away and the holes will end up being a lot bigger. You need to weld in new metal to fix the rust.

A1Judge · 07-03-2001, 09:19 AM

If you use filler, use USC All-Metal. It is a waterproof, aluminum filled polyester. It is sort of a cross between regular filler and Lead. It works great.

For protecting inside with POR-15, spray it in behind the support brackets. Use a GOOD respirator when spraying, and don't get it on your skin!

Don

Dennis B · 07-03-2001, 11:57 AM

I would stay away from the filler Richard. It makes a much better job if you remove all the rusty metal and weld in your patches. Remember to SPOT weld only. Use spots about the size of a pea and cool it immediately with a wet rag after each spot weld. Leave about 1/32" gap between your filler piece and the roof panel and do not run your spot welds next to each other, always move the weld to another area until all the spot welds are joined, grind lightly ,fill if needed, prime and paint. Shoot underside with POR15 and prime. Everyone has there own method but this worked well for me.

Richard Ohran · 07-03-2001, 12:20 PM

I guess the choice is: screw it up now, or screw it up later. If I try the bondo approach now, I'm won't have any warped panels to deal with, but it might bubble down the road. When it does, I can sandblast the bondo out of there, and start warping the panels then. Who knows, with the 15 percent humidity we have around here, it may never be a problem.

BTW, I love to sandblast. The best kilobuck I ever spent was for a fresh air system. I use it for painting and sandblasting, and climbing around in insulation filled attics.

Richard/Vegas

Richard Ohran · 07-05-2001, 12:17 AM

Today I found the real rust. The trunk floor is riddled with rust holes. It's still strong enough, but lots of ventilation. A guy from a local landcruiser group claims everyone around here is using Herculiner with great success. They get it at KMart. Has anyone tried that?

Richard/Vegas

MitchGM · 07-05-2001, 12:29 AM

<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by Richard Ohran:
A guy from a local landcruiser group claims everyone around here is using Herculiner with great success. They get it at KMart. Has anyone tried that?<HR></BLOCKQUOTE>

Herculiner? What's it used for?

'ol Pinion head · 07-05-2001, 01:02 AM

Richard,
The Landcruiser guy sounds like my kid brother. My brother has (2) rusty POS FJ40's & also thinks spayin bedliner product & undercoating are the way to get rid of rust [img]/infopop/emoticons/icon_frown.gif[/img] Needless to say, I have given him a lot of grief over this & he is finally wising up & ordering new sheetmetal.

If your bird is going to be a really nice car, it deserves a new trunk floor. Problem is often the lower rear tail panels have rust as well & cutting the trunk pan out usually leads to more involved work.

Richard Ohran · 07-05-2001, 02:43 AM

All the rust seems to be related to the vinyl top. As near as I can tell so far there is no rot on the rear quarters. In fact, it appears to be limited to the center two sections of the trunk floor. I might be able to get away with just chopping them out. We'll see after I finish the sandblasting tomorrow. Apparently, small amounts of water leaked through the panel above the trunk, and puddled on the trunk floor. So, the rust was generated internally, not from general exposure from the bottom. Nevertheless, it looks like replacing the trunk floor is fairly major surgery and difficult to do without inflicting more damage than is being repaired. If it will work, I'm inclined to try something like a POR-15 repair. It won't affect my ability to replace the complete trunk floor later if I so decide. If it wasn't letting exhaust fumes into the passenger compartment, I wouldn't even worry about it now.

Mitch, Herculiner is something they put on pickup beds. It's pretty durable stuff.

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