A few years ago I media blasted my 'cuda project. With a small air compressor it was a very slow process; however eventually I completed the entire project as was very satisfied so I moved onto sheet metal replacement which I completed and then I put everything in primer.

Recently I completed filler work and am close to respraying everything with primer. While sanding on the deck (which I thought was in good shape) I noticed a few areas stayed shiny and upon closer inspection I noticed these dips occurred only at the locations I was able to hit with the blaster from both sides so it is obvious that I created these warps during the sand blasting phase.

I have invested so many hours in this project that I am tempted to just buy a new deck; however I guess I have nothing to lose by trying the heat and then cold water soaked rag method to shrink the metal. How much heat do I apply and can I do this with a small propane torch? If not I have seen the MAPP gas torches. Will MAPP gas do a better job?

I always used a oxy/acetelyne torch.

You could try the Mapp gas BUT it is important you heat the spot quickly and quench it.

You don't want to heat the metal slowly and allow the heat zone to spread out past the repair area.

Thanks for the tip. I'll practice with the Mapp gas on an old fender to see how quickly it heats up the metal before attempting this repair. It will be great if this works!

This is a common problem and a reason I only hand strip decklids and hoods. I have used Mapp gas before to shrink but I don't think it will work well for you here. I would think very careful shrinking with a disc would give better results. How much high solids would you need to build the decklid up?

Sheldon

I hate to say it but it is very unlikely you will wave that torch over that warped deck like a magic wand and it will come amywhere near straight, even if a person is very experienced with torch heat-shrinking. Part of the problem is no access to the back of the panel for dolly work. I think it is a case of either fill it with bondo, or use even more bondo after torching it. Might need to just replace. I've done a lot of heat-shrinking, and something like that will be wildly risky, a pure hit or miss.
-dulcich

If I understand you correctly, you stretched the metal by sandblasting and now you have a couple crowned spots? I have never been any good at metal shrinking so this is what I have resorted to doing. In the high point of the crown, cut a slit through the crown with a 1/32" cutoff wheel. Then bring the metal together to flatten the crown out and weld the slit up. If you're prepared to replace the deck anyway, you might want to give it a shot.

Ive blasted alot of cars with all kinds of media and know first hand what you are going through.....you will never get the right crown back in that area .....replace the deck.

My biggest concern was the "oil can" flexing. Since I already had the deck in epoxy primer I decided to try to shrink the metal just enough to get rid of the "oil can" problem with a hammer and dolly instead of the torch and wet rag method. As a rookie it took me awhile; however I was eventually able to get it tight. I am now using body filler. Hopefully with enough work I'll be able to make it look good. I'll never media blast another deck, hood, or roof skin with sand again. I have double checked the roof and I am very, very thankful it has no oil can issues!