Have 3 noticeable spots so far that have some pretty heavy damage, 2 are holes right next to the body mounts that were covered by spray foam and the other spot is just in front of the right rear wheel, one under the frame and one right to the right where my quickjack is mounted onto. Would it be worth it to try and do some weld repairs? If so would I need a torch or just a grinder and MIG?

Left body mount

Right body mount

Right rear

Righ rear #2

 

It's hard to see the damage by the #2 body mounts but the rust by your rear tires is fixable. if the rot is on the bottom of the frame and the top is still solid it can be fixed by someone who knows how to weld. all the frame pieces are available from vendors. i had to repair a spot similar to yours by the rear wheel only on the driver side and a few years before this repair i had to repair some rot on the left side frame but don't have any before or after pictures of that repair. since the repairs i have sprayed a few cans of the eastwood internal frame coating inside the frame on both sides to hopefully stop the rusting. as rusty as it looks it was still pretty solid, i hammered it pretty good with a screw driver and couldn't poke thru the car saw some winter driving in its very early days.
Pat

before:


after:

 

Magic


Rust/foam in your first pictures is on your birdcage. Fiberglass body panels are glued to this "birdcage". That rust is on your #2 body mounts. Rust areas may/maynot also be on your frame (below).

Water that caused that rust most likely flowed down from your windshield header (birdcage assembly that holds windshield in place.

Likely water leakage caused by rust-out of this header assembly. Remove inside upper windshield trim panels to assess damage.

Also likely, water damage (rust) extends back from #2 body mount area compromising your "rocker channel" part of birdcage. (Rocker channel is lower section of birdcage connecting front to back sections of cage.)

This section is covered by a closely fitting fiberglass facia. Water may have leaked in between these sections causing rust. That rust is likely invisible.

One way to detect it is by removing outer lower trim facia running from back of front tire to front of rear tire. Once off, whack sides of fiberglass trim with your hand. If rust flakes fall out, then that area is also compromised.

Look under dash for additional signs of rust - upper corners especially.

You might search this forum for "birdcage rust" - lots od information.

Repairs involve body off and perhaps removing glued on panels from birdcage to effect repairs.

If not DIY, then, depending on damage, cost of repair may easily exceed car's value.

Difficult choices, but get a good handle on extent of damage BEFORE you start.

Mapman

 

IF you need to cut metal look into a plasma cutter instead of a torch. When I was reviewing youtube videos recently for pointers on crossmember mods I saw a guy raving about his new plasma cutter from Jegs....so I ordered one. So far it has been wonderful. Take a look.

 

You certainly don't want to use a torch to cut out the frame rust - that would be a really bad idea. But you also don't need a plasma cutter. The thickness of the steel in the frame is light enough that the frame cuts easily with a high speed cutoff wheel.. You get a nice, precise cut that's quick and easy to do. Clean it up with a high speed sanding disc and a grinder and you're ready to weld. No problem.

Lars

All cuts on my frame done with a high speed cutoff wheel:

 

Good point about using cutting wheels ..... but if you need to cut metal that plasma cutter is so cool... and I already owned an oxyacetylene rig..... still glad i have it since I can do brazing with it.

 

I would also add a small reciprocating saw for tight areas that a cut off wheel can't reach...
Many of Vettes have burned to the ground along with the garage from torches...Fiberglass is flammable...

 

I acquired a 72 convertible that looked really good. Of course as time passed I kept discovering rust areas and bit the bullet. Took the body off and fixed the frame similar to the pictures of Lars' work. Also exposed the birdcage and replaced the rusted corners. The vendors have alot of useful patch parts and there are a bunch of sellers with parts on CL and ebay that are also useful. I bought a welder, taught myself how to weld and had at it. Its a lot of work but I enjoy it and it is very doable in your home garage. Unless you have a rare, valuable car the cost for a shop to do the work is not feasible. If you don't find all the rust and address only the currently visible areas I suspect you will have continuing issues.