How do I fix this? I have a mig welder, could I weld on a big fish plate? I don't have a huge budget...

The rust is in front of the rear wheel on the drivers side.

http://flic.kr/p/dGxVF4

 

I'm not familiar with the '75 but on my '81 that particular area is one of the major strength areas of the frame. I'm sure it can be fixed but I would pull the body off for a couple reasons, first, to see how far the damage extends. and second, it would make the repairs much easier.

I don't think just a patch will be sufficient.

I'm sure others will chime in soon

 

There's no cheap easy fix for that: You have to cut the frame rails and weld in new sections. Only way to do that is to pull the body, sandblast the frame, and start cutting & welding.

I thought I could get away with some easy welding from the bottom of the car, too, but had to admit reality. Here's the same area of my frame after I got the body off:


Only way to see what's good and what's not is to sandblast the thing. Here's the 'blasted frame with stiffening bars welded in to keep it from twisting when I cut the rails out:


SawZall is a great tool - cuts that frame like butter!


Cut frame showing all the rust holes that were visible only after sandblast:


New frame rail section clamped in place for welding. All the major Vette suppliers sell the frame rail sections in various lengths:


New section welded in:


This is the only way to do the repair right - there's no way you're going to repair that amount of rust damage with the body on the frame. My basic frame with the rust repaired and ready for paint:


Final assembly and almost ready for the body again:


Good luck with the project. If you're not wanting to pull the body, you might consider selling the car and finding something with less rust: You have a massive project ahead of you repairing what you have there...

Lars

 

can you weld ,or have a friend that can mig weld ?

 

Yes I can weld pretty well and know a few people who are probably better welders than me.

 

It's worse then you think. Mine looked similar, but I knew I needed a frame. It had already been "patched" from below. ...I considered just finishing the car the way it was, but decided to do it right and pulled the body for a new frame. When the body started coming up, the back half of the frame started going down. Never thought it was THAT bad. The body was basically keeping the frame together.

 

Nice job and nice write-up, Lars.

 

You are only seeing the "tip of the iceberg" looking at it with the body on. The frame rusts from the inside out. When you see a oz of rust on the outside, there is a lb of rust on the inside. I'm not referring to surface rust... I'm referring to rust-thru... NY Style.

 

I have a 68 and had the same problem, frame rot on drivers side in front of rear wheel. Upon futher investagation, things got worse, also found the birdcage was rusted in the same area. You should check the birdcage in thes same area. I now have a major project on my hands. I purchased another 68 frame and will be repairing the birdcage.

 

Thanks Lars. Great post. Very informative. Thank goodness I do not have that problem.

 

Sorry, but if you want to play you got to pay. If you're over your head maybe best to sell.

 

If anyone needs a frame and or birdcage, PM me.

1981 body & frame getting ready to go to scrap in OHIO.

 

This showed up on my local craigslist. Seems like not a bad deal and could save someone a lot of work.
http://corvallis.craigslist.org/pts/3524405542.html

 

if I tap on my frame rust scale falls from the frame holes.I plan on buying a new frame soon.

 

I have a pair of 1976 Corvette frames for sale. Rust free tx frames. $500 each. PM if interested.
It is easier to swap your suspension over than fix your original frame