I have the new jack tube welded in place and am about to add the "pyramid" post support. Once I do so, an air pocket is created behind the support. What's my best bet for treating that area and the back side of the support before welding? Undoubtedly, most coatings will burn off due to the heat.

Should I consider maybe weld-through primer or just leave alone and count on the fact that it'll be another 40 years or more before it rots away again since the car is not my DD (yet) and will be sealed up way better from the outside when I'm done than it was from the factory?

Brilliant!

Why bother keeping the jack tubes and pyramids when all they do is trap moisture. Leave them off and use a scissor jack that will fit inside the doughnuts. Unless of course you're one of them CW's.
Cheers, Elliot

On my car the factory had drain holes on the supports to keep the inside from condensing and holding moisture. I would at least paint it with weld through primer then when finished spray wax inside the cavity or maybe the new eastwoods internal frame coating.

My post from '05

What we do in my restoration shop is clean, treat/arrest the corrosion, repair any corrosion that involves very heavy pitting or perforation, treat with phosphoric acid wash, rinse, dry, and paint. We use a undercoating kit that can be purchased at JC Whitney, Eastwood, and other auto supply houses. We treat the entire car, that is all the dead air spaces, boxed support members, etc.

First remove the control cables, and shift mechanism, as well as the pedal cluster, and most of the interior. Mask off the wiring harness with plastic and masking tape. Clean out the tunnel with compressed air and a shop vac. Manually scrape whatever you can reach with wire brushes, stainless toothbrushes, etc. Next you need very hot water and cheap automatic dishwashing detergent (like cascade). You don't want to get this on finished surfaces, as the trisoduim phosphate can dull painted surfaces. Mix up hot water with the detergent, and spray in into the tunnel. With the undercoating kit you get spray wands and different nozzles to blast in the corners, etc. Again, use the shop vac to remove the water. Next rinse with clean warm water, and clean this up. Blow dry with compressed air and the undercoating wands and nozzles. Check out the cleaning job with a light and a inspection mirror, make sure everything is nice and clean. Let it dry for a few days. At this point a little flash rust isn't going to hurt anything. Now it gets more fun! You can use Ospho, Oxysolve, any corrosion treatment with phosphoric acid that leaves a phosphate coating. You mix up the acid as directed, and after you've donned your safety goggles, respirator, and rubber gloves, you spray the area with the acid mixture. Most of them require liberal dousing, and you want to keep it wet for several minutes, longer if you've got more serious corrosion. Next you rinse the acid off with water, and clean it up. Blow it dry. Let it sit for a few days. Last you can use the same undercoating kit to blast your favorite corrosion paint over the treated areas.

This is alot of work, and makes a big mess, but it's the best thing you can do to mitigate corrosion. It's also a good thing to do if you've welded on structural supports like the GT stiffening kit, Mayeur kit, etc. If you don't treat the backside of a panel that you've welded, it will rust.

A thread: http://www.914world.com/bbs2/index.php?sho...=87664&st=0