C3 Frame sag
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Joined: Apr 2015
Posts: 57
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From: Orlando
C3 Frame sag
Greetings
I am looking at a 79 c3 mostly stock corvette. It says 63000miles, but I think it’s 163000
The only thing I am concerned about is frame sag.
I was told that these had frame sag problems, causing waterleaks
I am going the have it checked out by a pro, before buying.
My questions are:
1. Should I worry about this in the long run?
2. Is there a way to keep from getting frame sag?
3. Is there a way to fix the sag.?
4. Is there (weld on)kits for reinforcing theframe?
Thanx
A
Team Owner
Joined: Sep 2006
Posts: 31,301
Likes: 4,389
From: Westminster Maryland
Hi A,
First post!!! Welcome!
The 68-82 frames can be susceptible to serious rust problems.
One of the most likely places for this to occur is right in front of the rear wheel.
If the rust is extremely advanced the frame can begin to fail at the point it starts to raise up over the rear suspension and half shafts.
When this happens sometimes the car appears to be sagging in the middle. This causes problems far more serious than leaks.
I'd think your 'pro' would know all about this, and also the long list of others things that need to be checked in a car you're considering purchasing.
There are many Corvettes that don't have rust problems so there's no reason to consider one that's rusty.
Good Luck!
Regards,
Alan
First post!!! Welcome!
The 68-82 frames can be susceptible to serious rust problems.
One of the most likely places for this to occur is right in front of the rear wheel.
If the rust is extremely advanced the frame can begin to fail at the point it starts to raise up over the rear suspension and half shafts.
When this happens sometimes the car appears to be sagging in the middle. This causes problems far more serious than leaks.
I'd think your 'pro' would know all about this, and also the long list of others things that need to be checked in a car you're considering purchasing.
There are many Corvettes that don't have rust problems so there's no reason to consider one that's rusty.
Good Luck!
Regards,
Alan
Team Owner
Joined: Jul 2004
Posts: 40,422
Likes: 792
From: Redondo Beach, California
Another frame "sag" situation is the crossmember that runs under the engine crank pulley...the crossmember that basically interconnects the front wheel spring coil towers. Especially with a big block, road shock can cause this crossmember to bend, which means that the spring control towers bow inward with the result that a lot of shims have to be added to make the front wheel vertical to the road. I've only known of one person who actually had a problem with this situation...so I don't think it's something you should be really worried about. The solution for this problem is a "speader bar" which attaches to the top of the spring towers to prevent them from deflecting inward. I think Alan's comments about frame rust is the premier concern.
Le Mans Master
Joined: May 2006
Posts: 5,814
Likes: 414
From: Pittsburgh suburbs Pa.
You should also have the bird cage checked for rust which is a major job to repair. That is the main metal structure that the fiberglass fastens to. There are many posts on here on how to check these areas.
Safety Car
Joined: Sep 2007
Posts: 4,458
Likes: 331
From: Indy Indiana
Greetings
I am looking at a 79 c3 mostly stock corvette. It says 63000miles, but I think it’s 163000
The only thing I am concerned about is frame sag.
I was told that these had frame sag problems, causing waterleaks
I am going the have it checked out by a pro, before buying.
I am looking at a 79 c3 mostly stock corvette. It says 63000miles, but I think it’s 163000
The only thing I am concerned about is frame sag.
I was told that these had frame sag problems, causing waterleaks
I am going the have it checked out by a pro, before buying.
slightly mis-stated..
Water leaks and drain off design in these cars cause rustout problems.
this is especially true of rust belt cars that have been driven alot thruout the decades in the rain and snow and salt.
if you jack up the car and the door won't close or open or you see a very wide gap in the rear part of the door gap to the body, then your frame is weak and your car is being held together by your door striker post.
don't even waste your time or your pro's time... he will tell you not to buy it. run forrest run..
unless the car is very cheap $$.
fixing it means lifting the body and sliding a new frame under it... some say the weak spots can be replaced with frame rail kits.. But I would presume that there are multiple rustout problems in other places on the car.
its a 5 figure repair. I would spend that 5 figures on a better condition car.
