We ordered some new inner frame horns for a 1974 big block but the new horns do not match the old ones (or the frame). I've attached some pictures to show the difference. The old frame horns have obviously been modified but we have no way of knowing if that was done at the factory or hacked together by some previous owner. The back welded on nuts on each side have been moved forward which does match the distance between them of the new frame horn but lining them up with the old position places the frame horn about 3/4 inch too far forward to weld to the front cross member and puts the sway bar mounts too far forward.

This picture shows the correct alignment of the front of the horn but too short at the back.


This picture shows the gap at the front cross member when positioned to match the bumper mount holes. If we slide it back to the cross member the sway bar nuts are in the same position as the old one but the bumper mount holes do not match.


This picture with the old left and the new right shows how those lower nuts and the back of the horn line up but the front is too short.
The outer frame rails are one piece and there are no signs they've been changed. You can also see on the old one where the large welded nut for the bumper mount has been moved closer to the front.
It's like there is an inch missing from the middle (well, missing from the top part but not the bottom).


Can someone help us either find frame horns that match the old ones or send pictures of their frame horns for comparison? Maybe will will have to cut these ones up and weld them together to match the old ones, but if it's possible I'd prefer some that match our frame.

 

Let's start with your question about whether the old frame horns, were modified by the factory. I don't think so. It's not likely that anything would ever leave GM, looking like those. It seems much more likely, that the mods to your old frame horns, were done by everyone's old friend "Bubba"!

What kind of shape is your frame in? I wonder if the car was hit at some time, and either the frame was replaced or improperly repaired. This could explain why a previous owner, had to do so much "work", on the frame horns.

I have a number of original front frame horns and extensions, including some 74 pieces, at work. I'll try to look through what I have, in the morning, and post some pictures if I have a pair of 74's.

 

gbvette62 were you able to find the horns and get pictures?

Pictures of horns from other years could be helpful as well in case we can see one that matches.

 

I thought that I had a couple of those inners laying around loose, that had been removed from an old frame, but haven't found them yet.

I do have a 74 frame, from a car that was parted years ago, and they are still in it. I'll try to get a picture of them tomorrow.

I have an old 80 frame at the shop, that still has them in it too. From a quick look, they appeared to be the same in both frames.

None of my older Corvette Parts Books, list that part for a 74 older Corvette, at least not that I could find. The 79 and later books do list them, but just for 75-82 Corvettes. Chevrolet may never serviced that part separately, for the 74 and earlier frame. It may have only been available as part of the entire frame.

I'll try to post get pictures in the morning, and maybe take some measurements too.

 

Mystery solved!

We've looked under a lot of C3 corvettes over the past while but as we get closer to the final painting on that part of the frame I did a very concerted effort searching corvette frame images this morning. I pretty much accidentally looked at some C2 frames and noticed it was a closer match. We have searched for any signs of modification near the frame horn area in case some one modified them but it all looked original.

After seeing the close match with the C2 horns looked for other possible changes to the frame and found a seam near the front of the widest part of the frame. We are now assuming that some time in the car's past the entire front part of the frame was replaced with a 65 to 67.