How common is frame repair on vintage muscle cars. Hearing that frames for vintage cars are difficult to find, is it common to find restorations with frame repairs and how does one asses quality?
Thanks
Wayne

 

These frames are mild steel and are easily welded. Repair is a non-issue, ASSUMING you can find a frame shop that has a clue. Unfortunately, there hasn't been a body-on-frame automobile built in decades, so most shops only have the expertise and equipment to repair unibody cars. I'd suggest a truck frame shop.

Used replacement frames are not difficult to find, at least not for A-body cars. Expect to pay $500-$1200 for a good hardtop frame (depending on whether it's been sandblasted and painted or not) and upwards of $1500 for a boxed convertible frame. Often you can buy a parts car with a a bad body but a good frame for considerably less than buying a frame alone. Go figure.

 

Thanks Joe, so I can assume that looking at a vintage auto with a frame that has been repaired and disclosed by the owner is ok. However who did it and how is important. Then again one must be vigilant when checking out the car to check for rust holes, soft spots and general conditions. I have been alerted by several net articles to check the rear axle areas but no other areas. It was also suggested to bring along a small ballpeen hammer. Any suggestions?
Wayne

 

That's a slightly different question. First, it depends on the specific car, as each has it's own rust-prone areas. Boxed sections are the areas that trap salt and debris and thus rust out. The specific locations depend on the design of that particular frame. For example, A-body convertibles with boxed frames are prone to rust directly below the front of the doors. G-body cars are prone to rust in the rear frame rails behind the axle (this is so common that repro frame rail sections are available).

Second, was the repair for rust or for a crack? I'd be less worried about a crack repair, as usually the metal is still full thickness. Rust is rarely confined to a single area, so even if a patch was properly installed, how much has the remaining original metal been thinned out?

Welds need to be carefully inspected. First, be sure there was proper penetration. Second, look for undercuts at edges. The right way to weld a patch is to use a runoff tab at the edge of a flange to prevent the undercut, then grind off this tab. If reinforcing plates were used over a weld, the edges of the plates must be tapered to avoid a single stress discontinuity.

GM publishes upfitter guides for their truck lines that provide information to aftermarket companies who modify trucks for commercial uses. The Chassis best practices guide includes a very informative section on frame welding (see pages 14-15 in particular):

https://www.gmupfitter.com/files/med...hss_020815.pdf

 

Joe, thanks for the info. I will hopefully see the car in question in the next 3-4 weeks. I will check it completely and record with pictures for discussion hopefully. I am looking forward to this with some apprehension. BTW where are you located?
Thanks
Wayne

 

Joe for what its worth our laser measuring system will do old cars well into the 1950's and the machine tells you where to put the laser pick ups so that the machine can read the dimensions and tell you which way to pull the frame. The old tram gauge method still works but can be flawed. Most trucks still have full frames you would be amazed how easy they will get tweaked ir diamond out. Also pulling on newer frames is not always easier than older cars due to the fact they have energy absorbing areas that will hold energy .I know when i crashed my 72 i had to pull the driver side rail and it moved pretty easily. I have had newer cars with less damage on the frame rails that took more effort. Just my experience.

 

Thanks, that's good to know. I'm impressed that the database goes back that far. I wasn't trying to imply that newer cars were easier or harder to straighten than older ones, just that unibody cars require different skills than full frame cars, and young techs may not have experience on older cars. Witness how many people don't know how to adjust points, for example.