[47 Coupe]

I tack welded my back fenders, cowl vent and hood halves on a 47 Chevy. I didn't weld them solid and then finished them with all-metal. That was several years ago and now the seams with the tack welds are showing. They were good for a while ( you couldn't see them). It seems like its worst when it hot like in the summer. Does the all-metal being mostly aluminum, expand and contract differently than the steel?

[baddbob]

The seams need to be welded solid before any filler gets applied. Being they were just tack welded they would have shown themselves regardless of what kind of polyester filler is used. It is all related to expansion and contraction and the flexing and movement that takes place at the seam when only tack welded. Also, I wouldn't use the all-metal filler anymore. I've done some testing with it over the years and found it less durable and moisture resistant than the fiberglass reinforced type like Everglass. For any areas then need extra strength or requiring a fill 1/8"-1/4" in thickness then definately go for Everglass or Marglass or the original Duraglass then finish it off with a regular filler and or polyester glaze. The silver fillers have come and gone in this area-road salt capital of the world... Weld your seams solid if you plan to finish off with filler or learn how to use bodysolder.

[Bee4Me]

"Someday" Bob, I hope we get to meet. Your advise is always "on the money" and YOU have taught ME well my friend. Between Barry,You,Shine,and JimC,I just may become the painter I think I am.The "work" sure shows it anyway.
Bob's right as usual. Glaze's don't do much for "stremgth" areas.You need a reinforced filler but as said,you NEED to FINISH your welds as you ARE replacing the METAL integrity of the panel and even filler's won't replace SOLID metal.

[timothale]

In the old days we had asbestos based putty that we rolled into a bead then laid down next to the weld area to absosrb heat and prevent warpage. you could remix water and a little bit of oil and reuse. I bought some new Heat Putty at my welding supplier and My son used it on his 22 dodge lakester and It really helped. after using it it starts to dry out. we put the used stuff in another bottle. when it gets half full will try to remix with water and see if it is reusable like the old stuff.

[Old Fool]

Sorry to hear you got duped with the allmetal scam. The aluminum powder in it does nothing more than color it, and it is not all metal. It is polyester just like most other"bondos"

MSDS sheets are your friend, a great source of the contents of that can of magic potion.

Weld, grind, epoxy next time . it will last a lifetime

[47 Coupe]

Thanks for all the replies. They areas didn't crack, its just that under certain conditions you can see the area that were filled.

[baddbob]

Depending on how far apart your tacks are they may eventually crack-this is from movement as both pieces are moving during expansion and contraction. Had they been welded solid there wouldn't have been any movement. Also your welds should be ground flush with the base metal or as close to flush as possible. Another phonomenon that can happen when pushing filler into an open seam is moisture absorbtion from the backside into your filler-polyester illers are porus-add the heat of the sun and you're going to see some additional expansion of the filler and mostlikely corrosion later on if it was applied directly to bare metal. Weld your patches solid, use two coats of quality epoxy primer over the bare metal and do your filler work over that and it will last a few lifetimes.

[baddbob]

Originally Posted by Bee4Me

"Someday" Bob, I hope we get to meet. Your advise is always "on the money" and YOU have taught ME well my friend. Between Barry,You,Shine,and JimC,I just may become the painter I think I am.The "work" sure shows it anyway.
Bob's right as usual. Glaze's don't do much for "stremgth" areas.You need a reinforced filler but as said,you NEED to FINISH your welds as you ARE replacing the METAL integrity of the panel and even filler's won't replace SOLID metal.

Mike, If I ever take a roadtrip your way I'll definately stop in for a cold one! I wish I had some of the artistic talent you've developed these last few years.

[redsdad]

Originally Posted by baddbob

Weld your patches solid, use two coats of quality epoxy primer over the bare metal and do your filler work over that and it will last a few lifetimes.

Bob, regarding the hood. I am on my second hood. The PO welded it, probably went from the nose to the cowl in one continuous bead. The back corners stuck out so far from the body, I gave up thinking about fixing it and found another.

Anyway, I have been toying with the idea of tack welding it into one piece and then leading the seam. There is about an 1/8" depression where the trim strip used to go which will have to be filled anyway. With the flexing and impact it will receive opening and closing, I was thinking lead would be a better choice anyway. Any thoughts on tacking and leading?

[baddbob]

Lead will work but to do it right you have to make sure everything is perfectly clean and flow the lead right through the seam so there is no trapped acid to haunt you later.