C3 Frame Differeces??
Thread Starter
Drifting
Joined: Aug 2001
Posts: 1,606
Likes: 14
From: Vacaville, CA
C3 Frame Differeces??
Can anyone explain the Frame Differences between model years...Coupe and Convertible.
I know that the '68 had a weak spot at the rear crossmember behind the seats and GM stiffened that area by placing in 45 degree frame gussets on the '69 and follow-on years...
But other than that are there any other differences between model years and body styles?
Thanks!
I know that the '68 had a weak spot at the rear crossmember behind the seats and GM stiffened that area by placing in 45 degree frame gussets on the '69 and follow-on years...
But other than that are there any other differences between model years and body styles?
Thanks!
Last edited by BlackRocket; Aug 2, 2017 at 05:29 PM.
Team Owner
Joined: Sep 2006
Posts: 31,272
Likes: 4,362
From: Westminster Maryland
Hi BR,
68-72 convertibles and coupes both used the same frame.
Frames for cars with 4-speed transmissions had a welded in place transmission cross member.
Frames for cars with automatic transmissions had a bolt-in transmission cross members.
There was no difference in frames for big block or small block cars.
Regards,
Alan
The 2 diagonal braces at the frame 'kick-up' on a 71 frame.
68-72 convertibles and coupes both used the same frame.
Frames for cars with 4-speed transmissions had a welded in place transmission cross member.
Frames for cars with automatic transmissions had a bolt-in transmission cross members.
There was no difference in frames for big block or small block cars.
Regards,
Alan
The 2 diagonal braces at the frame 'kick-up' on a 71 frame.
Last edited by Alan 71; Aug 2, 2017 at 06:01 PM.
Safety Car
Joined: Nov 2008
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From: Seattle Washington
The late model 80-82 Frames were rumored to be lighter than the early Frames but I'm not sure if this is really true or not. All Late model Frames have a removable Cross Member no matter what Transmission. The Cross Member is intended for a single Exhaust and hasn't the Holes for it to pass threw. As these Cars used the Dana 44 rear end with the Batwing the Mounts are different.
Le Mans Master
Joined: May 2003
Posts: 8,877
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From: Fernandina Beach FL
2023 Restomod of the Year finalist
2020 C3 of the Year Winner - Modified
How about this-
Changes through the years-
http://www.71corvette.com/frames.html
and this- Specs
http://www.bairs.com/page291.asp
Changes through the years-
http://www.71corvette.com/frames.html
and this- Specs
http://www.bairs.com/page291.asp
Thread Starter
Drifting
Joined: Aug 2001
Posts: 1,606
Likes: 14
From: Vacaville, CA
So am I correct is stating that the "Frame Kick-up's" were not on the '68 Frame but were added beginning in '69 due to the single joint attaching the tail section to the lower rails as being a weak area?
Thanks again!
Thanks again!
Le Mans Master
Joined: Oct 2007
Posts: 7,451
Likes: 974
From: RI, Now Franklin/Nashville TN
I will have to look closely at those diagrams but the basic frame of all 63-82 corvettes was essentially the same...I am going to look at the specs carefully so when this question comes again, which it does, we all have the factual answers. Certainly the 69-82 frames look almost identical with some very very small (low single inches) differences.
The myth that the 80-82 frame was lighter is not true. All the C3's used the same type of steel for the frame and you see from the images that 78-82 frames are the same. The only way for the later frames to be lighter would be to use a different material like aluminum and that did not happen at GM until the 21st century with the C6 corvette with the Z06/ZR1's having an aluminum frame and magnesium engine cradle unlike the base/Grand Sport C6's that had a steel frame and I believe steel engine cradle. The weight savings on the 80-82 came from the aluminum diff/batwing supports and thinner fiberglass for the body, not from the frame...
The myth that the 80-82 frame was lighter is not true. All the C3's used the same type of steel for the frame and you see from the images that 78-82 frames are the same. The only way for the later frames to be lighter would be to use a different material like aluminum and that did not happen at GM until the 21st century with the C6 corvette with the Z06/ZR1's having an aluminum frame and magnesium engine cradle unlike the base/Grand Sport C6's that had a steel frame and I believe steel engine cradle. The weight savings on the 80-82 came from the aluminum diff/batwing supports and thinner fiberglass for the body, not from the frame...
Last edited by jb78L-82; Aug 3, 2017 at 07:01 AM.
Thread Starter
Drifting
Joined: Aug 2001
Posts: 1,606
Likes: 14
From: Vacaville, CA
Just searched images of a 1968 Corvette Frame and the pictures all show NO rear kick-ups!
Link:
https://images.search.yahoo.com/sear...g&action=click
Link:
https://images.search.yahoo.com/sear...g&action=click
Last edited by BlackRocket; Aug 3, 2017 at 09:34 AM.
Thread Starter
Drifting
Joined: Aug 2001
Posts: 1,606
Likes: 14
From: Vacaville, CA
Searched 1969 Corvette Frame and the pictures all show the rear kick ups...
Link:
https://images.search.yahoo.com/sear...g&action=click
Link:
https://images.search.yahoo.com/sear...g&action=click
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Drifting
Joined: Mar 2013
Posts: 1,926
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From: Lansing MI
The frame braces were added part way through the '68 production run. I believe they were added to frames beginning around April of '68. My August '68 has them, but who knows if my frame is original.
Le Mans Master
Joined: May 2008
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2022 C3 of the Year Finalist - Modified
The rear structure of rubber bumper cars is definitely different than chrome bumper cars. Especially from 75 up the bumper protection shocks fit inside the frame, so were much bigger in size. 80-82 was different.
The side view diagrams shown above for later models is incorrect in the same area. They may be correct dimensionally, but the image imply they are the same shape and they are not.
The side view diagrams shown above for later models is incorrect in the same area. They may be correct dimensionally, but the image imply they are the same shape and they are not.
Le Mans Master
Joined: Oct 2007
Posts: 7,451
Likes: 974
From: RI, Now Franklin/Nashville TN
Pretty much everything you want to know is here:
http://www.71corvette.com/frames.html
The frames from 68-82 are basically the same with some minor tweaks detailed here^^^. Again, the 80- 82 frames are NOT lighter than the earlier years...the weight reduction for 80-82's came from other areas, NOT the frame!!!
http://www.71corvette.com/frames.html
The frames from 68-82 are basically the same with some minor tweaks detailed here^^^. Again, the 80- 82 frames are NOT lighter than the earlier years...the weight reduction for 80-82's came from other areas, NOT the frame!!!