C3 Frame crack

[Yves Thaens]

Hi,

I have a 79 donor car that I'm disassembling right now. Behind the spring towerd there is a large crack. It is a clean straight crack. You can see the frame bending and the crack opening when stress is put on the frame. Just wondering if this is a common problem. Lucky for me this was just a parts car, although I was planning on selling the frame.

Yves

[Chuck S.]

Re: C3 Frame crack

This is NOT a common problem to my knowledge...in fact, this is the first I have heard of a C3 frame breaking. It sounds like fatigue failure; look along the crack for an initiation point, such as deep undercut in a weld (over-melting the base metal at the edge of the weld), a hole, or some other weakness that would be a stress concentration point. In any event, it sounds like the frame spent a lot of miles on bad roads.

Compared to other C3 frame restoration repairs, this one should be simple...you can probably have the frame weld repaired, and sell it for nearly what you could have gotten anyway. From your description, a good pipe welder could do this repair to warm up for his morning coffee break. If you can't find a pipe welder, any good structural steel welder will do. The crack must be ground to a 90 degree groove (45 deg each side), then lay in good solid full penetration passes until the weld metal is above the surface. Grind the weld metal flat with the surfaces, and paint...a frame many C3 restorers would love to have.