Hi all,
I have been trying to adjust the fit of my front clip, and have noticed that the bolts for the frame extension were going through the holes for the bumper brace. After trying to fix that, I noticed that no matter what I do the holes will not all line up, even with the extension bracket completely unbolted. The car is a 1970, but for some reason I seem to remember the PO saying the frame is not. Would be bolt holes be different throughout the years, or should I grind out some of the holes on the extension bracket?

 

Hi ac,
Yes, it appears you have a later frame… from a car with a rubber bumper?.
Here's the typical installation of the frame extension and bumper bracket, (71).
It looks like the 2 holes you have the bolts in are actually for the 2 bumper bracket bolts.
The forward extension bolt is hidden behind the dimple in the bumper bracket on both the left and right sides.
Regards,
Alan

 

Alan......thanks for the pic.....I'm missing both bumper brackets!

 

I THINK I have two bumper brackets from a '72....anyone need them, PM me and I go look.....and take a pix of them to send email....

 

Here are the extension brackets from 69. The bolts are temporary but they were the same on the donor 69 also. this is without the bumper supports.
r

 

Yes I took those bolts out and got new bolts and nuts in the proper holes, but no matter what the 4 holes wont line up, so I am wondering if later model frames had different hole patterns? Or has someone else had this issue?

 

I believe if you check the frame books they will show 3 different repair front pieces, 68, 69-72(maybe 73) and then I think 73(74?) right up to 82
The cross member that bolts to the extensions changed in 72 (73?)
M

 

Frame repair sections (zip)

69-72




73-82



M

 

As far as I remember the GM replacement frames were for 68 through 74. Does anyone know if there is a difference in the front frame holes for the brackets attachment between the years 68-74?

 

I've had that issue before. It's been a while, but I remember just grinding out two holes in each bracket. I used an original frame to make some paint marks on the extension so I knew exactly where it should sit on the new frame, attached the 2 bolts that allowed my paint marks to line up, and then sprayed paint through the 2 holes in the frame so I had marks for my new hole locations.

And don't mess around with a dull grinder tip. If you don't have a sharp one go get one.

 

At one point in time, a few years ago, I knew all the details. i just forget now. After 1973, if you ordered a replacement NOS frame for a 68 to 73 Corvette, you unknowingly received a 1973 frame. I know...I ordered a NOS frame for a 69 in the mid 1970's and many, many years later...about 6 years ago when I tried to fit the frame extension brackets for my 70 on it, they wouldn't fit...slight mismatch with mounting holes. I had some 68 extension brackets and they wouldn't fit the "69" frame either. This mismatch with extension brackets was a mystery when I called Paragon and then also J&D Corvette.........when I called Volunteer Vette...I hit paydirt. Volunteer at that time had a lot of frame parts, after a little research, they told me that I had a 73 frame...I didn't know that..I thought it was a 69 frame.

For a body shop, the frame extension mounting hole differences would be a small problem...drill new holes or just weld in the slightly mismatching part. It's obviously more a problem for the do it at home guy.

I'm stretching my memory here. The 68 frame extensions to the frame were unique. The 69 to 72 frame extensions were similar I believe. The 1973 extensions were different. Just to repeat my comment...even though the extensions were different, if you ordered a replacement frame for a 68 to 73 from GM, you got a 73 frame. With a 73 frame, minor mods were required to fit the 68 through 72 frame extensions.

 

You unknowingly just answered the exact question I asked in my build thread a week or so ago. I have a nos '73 frame I want to put under my '68 and needed to know about the frame extensions.