Frame differences
Thread Starter
Burning Brakes
Joined: Mar 2001
Posts: 1,203
Likes: 146
From: dalton ma
Frame differences
I am an ignorant guest from the C! forum. I have an opportunity ? to buy a '71 4 speed conv with a totally rusted frame. Can someone give me a SIMPLE tutorial on the MAJOR differences in C3 frames ? I know about the bumper problem, how about manual vs automatic ? and single exhaust vs true duals, body mounts etc ? You get the picture. What should I look for , year wise, in a replacement used frame ? Thanks, Bob C
Team Owner
Joined: Sep 2006
Posts: 31,172
Likes: 4,250
From: Westminster Maryland
Hi c,
The frames from 68-73 will work fine.
4-Speed cars have the transmission crossmember that's welded in place, while automatic cars have a removable crossmember.
4-Speed cars will have a small bracket welded to the forward left side frame rail for the clutch z-bar to mount to, automatic frames won't have it.
On all these frames the center transmission cross member was set up for dual exhausts.
Good Luck!
Regards,
Alan
PS: … if the frame is so rusted it needs to be replaced what condition is the body 'birdcage', (steel structure) in?
71 Frame
Z-Bar bracket.
Frame rear… note 2 diagonal braces at kick-ups. 68 frames don't have them but they can be added.
The frames from 68-73 will work fine.
4-Speed cars have the transmission crossmember that's welded in place, while automatic cars have a removable crossmember.
4-Speed cars will have a small bracket welded to the forward left side frame rail for the clutch z-bar to mount to, automatic frames won't have it.
On all these frames the center transmission cross member was set up for dual exhausts.
Good Luck!
Regards,
Alan
PS: … if the frame is so rusted it needs to be replaced what condition is the body 'birdcage', (steel structure) in?
71 Frame
Z-Bar bracket.
Frame rear… note 2 diagonal braces at kick-ups. 68 frames don't have them but they can be added.
Last edited by Alan 71; Jan 21, 2016 at 07:33 AM.
Le Mans Master
Joined: May 2006
Posts: 5,814
Likes: 414
From: Pittsburgh suburbs Pa.
As Alan said check the birdcage. If the frame is real bad it could have rust in the birdcage. Not always the case but check before you buy. I bought a 69 convertible years ago that had a frame so bad that it broke in half when the body was unbolted and lifted , but the birdcage was perfect . It did need rocker panel supports though. The car only had 63k. miles but sat in a garage for over 20 years with water leaking through the walls and the water laid under the car causing frame rot .
Team Owner
Joined: Jun 2000
Posts: 38,923
Likes: 1,481
From: Southbound
Cruise-In II Veteran
Thread Starter
Burning Brakes
Joined: Mar 2001
Posts: 1,203
Likes: 146
From: dalton ma
Thanks all for your knowledge, however the '71 project is OFF. When pulling the car out of storage from the rear the only thing that moved was the portion of frame from the kick-ups back.
When that part of the frame came out it brought most of the glass with it. Never did check out the birdcage but after seeing what was really under the car I can only assume the worst.
The move destroyed whatever was originally worth saving. Ripped up all the rear suspension, E brake mech, exhaust etc. Car now is basically junk.
Was / is a numbers matching car but bare basic low horsepower no frills conv. Maybe next time. Bob C
When that part of the frame came out it brought most of the glass with it. Never did check out the birdcage but after seeing what was really under the car I can only assume the worst.
The move destroyed whatever was originally worth saving. Ripped up all the rear suspension, E brake mech, exhaust etc. Car now is basically junk.
Was / is a numbers matching car but bare basic low horsepower no frills conv. Maybe next time. Bob C
Drifting
Joined: Jul 2011
Posts: 1,697
Likes: 139
From: Syracuse NY
Thanks all for your knowledge, however the '71 project is OFF. When pulling the car out of storage from the rear the only thing that moved was the portion of frame from the kick-ups back.
When that part of the frame came out it brought most of the glass with it. Never did check out the birdcage but after seeing what was really under the car I can only assume the worst.
The move destroyed whatever was originally worth saving. Ripped up all the rear suspension, E brake mech, exhaust etc. Car now is basically junk.
Was / is a numbers matching car but bare basic low horsepower no frills conv. Maybe next time. Bob C
When that part of the frame came out it brought most of the glass with it. Never did check out the birdcage but after seeing what was really under the car I can only assume the worst.
The move destroyed whatever was originally worth saving. Ripped up all the rear suspension, E brake mech, exhaust etc. Car now is basically junk.
Was / is a numbers matching car but bare basic low horsepower no frills conv. Maybe next time. Bob C
2026 Loser of the Year
Joined: Sep 2013
Posts: 36,559
Likes: 7,006
From: New Or-leens Loo-z-anna
Thanks all for your knowledge, however the '71 project is OFF. When pulling the car out of storage from the rear the only thing that moved was the portion of frame from the kick-ups back.
When that part of the frame came out it brought most of the glass with it. Never did check out the birdcage but after seeing what was really under the car I can only assume the worst.
The move destroyed whatever was originally worth saving. Ripped up all the rear suspension, E brake mech, exhaust etc. Car now is basically junk.
Was / is a numbers matching car but bare basic low horsepower no frills conv. Maybe next time. Bob C
When that part of the frame came out it brought most of the glass with it. Never did check out the birdcage but after seeing what was really under the car I can only assume the worst.
The move destroyed whatever was originally worth saving. Ripped up all the rear suspension, E brake mech, exhaust etc. Car now is basically junk.
Was / is a numbers matching car but bare basic low horsepower no frills conv. Maybe next time. Bob C
Senior Member
Joined: Jan 2008
Posts: 12,146
Likes: 2,038
From: Easton, PA
St. Jude Donor '10
I have seen them break at the kickups as well and sad to hear another frame, and maybe whole car, lost to rust. I'm working on one of those now. Good luck with your decision.
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Safety Car
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From: Belmar NJ
I beg to differ, don't think of this as a disaster but rather an opportunity. Look into an aftermarket frame with late model running gear and LS motor/Tremec trans. As others have mentioned, you'll have 50K in a 25K car doing your original plan (and you'll have a car that still runs and drives like a 50 year old car when you're done). That same 50k will get you one of the sexiest body styles that runs and drives like a new car. Which would you prefer?
Drifting
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From: Deerfield Illinois
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I beg to differ, don't think of this as a disaster but rather an opportunity. Look into an aftermarket frame with late model running gear and LS motor/Tremec trans. As others have mentioned, you'll have 50K in a 25K car doing your original plan (and you'll have a car that still runs and drives like a 50 year old car when you're done). That same 50k will get you one of the sexiest body styles that runs and drives like a new car. Which would you prefer?