This question could apply to most mid to late 1960s GM cars.

The car spent most of its life in California and the unrestored frame and underbody is remarkably free of rust - almost like new.

One problem. The trunk floor, especially in the back foot or so has a dozen or two dozen pinholes up to 1/8 inch across. It seems that moisture sat under the floor mat for a long time and these rusted through from the inside out. The metal between the holes seems solid and dry. This is not generalized trunk rust.

Is it possible or advisable to weld the holes using a MIG welder and then grinding the welds off from the bottom and top? Or is there a better way to fix this? Since most of the trunk floor is fine, I would rather not cut out the trunk floor.

Thanks,
northern 396

I watched a good friend of mine weld up over 80 holes in one 34 ford coupe fender. This was after it was blasted revealing all the bad areas. His persistance paid off with a nice fender. graemlins/thumbsup.gif

The problem with pin holes is there's no way to tell the extent the rust has effected the metal from the center of the hole out. Normally you have a thin metal condition and as you attempt to mig the hole shut, the thin metal blows out and you end up with a hole large enough to stick your finger through. If the small holes are close together, I would say the entire area is thin and should be replaced.

Some have mentioned the use of epoxy putty to fill the small holes. I would only attempt this if I knew I had the rust contained. Sand blasting the area will knock out the loose and extremely thin areas. This may give you a better idea of the extent of the damage. Once the area is blasted and there appears to be enough area to patch, you could use the POR 15 products to seal and fill the small holes.

If your not going to cut and weld, then you might try the POR15 system. Basically grind or sand out all rust possible. Treat the area with their metal conditioner. Once dry, then paint with POR15 paint, then lay into the wet paint their fiberglass cloth and paint over it. After a couple coats of POR paint, the patch is solid like any fiberglass one. I did this once and the area is still solid and rust free after a year and a half. I'd check out their website for info. But the best is cut out all rust and weld in new metal.

I have been trying to convince my GTO friend to use a straight set of fenders with pinholes at the bottom for some time now. I told him that all he needed to do was to wirebrush and alcohol the fender then apply the POR 15 paint in several thick layers and just keep applying the paint and even let it pool in the holes. You don't even need to bother with the fiberglass cloth unless you have very large eraser size holes and even then, you can just use a regular piece of cloth and pour the POR over it. That stuff dries so hard and so solid - I have never seen anything like it. I had some in a can that I was dipping out of and I didn't use all of it, but left it open to the air. About 4 days later I cleaned up the can and that stuff was solid 2 inches thick! I even tried a hammer and chisel and could not shatter or chip it! Point - fiberglass can be hard to blend in if not done carefully - just pile up the POR to fill small pin holes.

I ran into this problem with mine too. The holes seemed to be small until i sand blasted the trunk to get it clean for welding. After the blasting was done the 1/8" holes turned into large holes. I bet if you blast the trunk you will have the same situation. I ended up cutting the trunk out and butt welding the new peice in. This will be a better repair and will last along time.