I have a 74 coupe, 350ci, 4-speed with a case of badly progressed frame rot. Just from looking at it from below, I think the #3 crossmember and both side rails for about a foot ahead of the kickups, needs replacement. I am in the process of lifting the body off the chassis to affect these repairs.

I do have two questions and i'd appreciate your help, comments & concerns:

1. Is it better to repair the current frame or go with a 'new to me' (good condition used) frame?

2. I've tracked down a frame locally (about 250miles away) that the guy says came from a '77 and is, has he says, is 'mint'. I haven't seen this frame yet. I'm concerned that there are differences between the two different year frames that would make this change complicated. Is there any difference between frames of these years...i.e. 1974 to 1977?

I'm not a professional welder by any means, but i have a stick welder and just purchased a MIG welder with this job in mine. I also do not mind tackling difficult tasks... after all the Vette is just as much a hobby as a pleasure to drive. My main corcern, as usual, is keeping the cost down.

Thanks in advance for any help and/or insight you guys can provide!!

 

You may have to make some changes in the frame if you purchase the used frame, I'll have to check this. If there are any, I'm sure they would only be minor changes and nothing serious.

Personally, I would base my options on how much money the guy wants for the frame. Used and new rails are available, the time and effort involved in welding them in can be intense.

If you do the welding method, I would suggest doing one bad area at a time and measure each body mounting bolt hole before you cut! This is a method to double check your weld after it’s done. We cheat on this and have a giant ole frame jig. It bolts in place by the body mounts and you can cut any section out you need and know it’s in the proper place when you go back.

Also, when you cut out your old sections be sure to save some of the old rail and use it for weld lips on the inside of the frame. This will allow you to tack up the frame before you run the bead. Make sense?

I would really look at how much he wants for the frame first. Doing the modifications if needed would be easy. Buying used or new rails may add up to the cost of what this guy wants for the frame.

We had a 77 frame here that was perfect and sold it for around 500.00. This should give you an idea and I’m sure prices can vary all over the place on these. I don’t have any frames left, and I was tickled to get rid of it.

Willcox

 

One thing to consider with the current frame is that if you have bad rust in the rails and differential crossmember the rest of the metal might have thinned enough to be stucturally unsound. If you can feel thick chunks of scale inside the frame the metal is probably pretty thin. If you repair the frame you have to make sure that you get the geometry right and all pieces aligned correctly.

I'm not 100% certain but I think the 77 frame should work with the 74 with maybe some minor modifications to the rear bumper mounts. The 74 frame was an evolution of the 73 with modifications to the rear for the crash bumper. 75 and up had the newer square openings for the bumper ram formed into the frame rails rather than added on. If you do a search for frames you will find much more info on the subject.



Rick B.

 

If you have locallized areas of rot, it may be easier to just repair what you have. Changing everything over to a new frame is a big job on its own. But, if the bad rust is just about everywhere, you'd be better off to start with a good frame and prep it for long term life (since it is already 'bare'). Even if there are some minor repairs that need to be made on the 'other' frame, it would be better than tediously trying to rebuild a rotted one. Research this topic pretty well; there are some strengthening improvements you can make to the C3 frame once you get down to it.

 

Was talking to him yesterday and he says he wants $2500 for his '77 frame.

 

For that money it should be better than "mint"!I would expect it to be blasted,painted and a couple of new parts thrown in...
Once you get the body off,you will see if your frame is worth repairing,just post a couple of pics and you will get all the opinions you'll ever need.

 

Dang thats a bunch......I have a nice bare 76 for $1000

 

Seems a bit to high to me!

Willcox

 

the 74 frame is a frame all itself, to use a 75 and up frame the rear section (about 18" - 24") has to be grafted from your 74 frame

Rear of 74 frame


Steve

 

Here are a few photos of the rusty areas taken from under the car before i started removing stuff in preperation to lift the body........

 

All I see is a Red X

 

Ok.... that didn't work to well!

Try this link: http://s469.photobucket.com/albums/r...unt74/Chassis/

 

Mine didn't look that bad from the bottom and when I pulled the body off this is what I found



Looking at picture #2 bubba's been at that frame

Steve

 

WOW....

Did you fix that yourself!! Have any photos of the repairs?

 

I used another frame, didn't even try to fix that one as the other side was just as bad if not worse


Steve

 

stpman if a guy plans to not use the 74 bumper and you use the fiberglass bumper that wont be using the absorbers is it still necessary to graft on the 74 frame section?

 

Hey your's seems pretty solid compared to mine lol. I'm keeping an eye on this thread since I'm in the same boat with my '74.

 

I would say no

 

I thought I had you guys beat with my ex c3 that I sold in '07.. but wow, I guess not!

 

also If you have frame rot you probably have this problem also...