I've read a lot of threads on this topic, and there seems to be varying opinions. I'm not sure if this is a non-issue or significant. Figured I'd ask the experts what, if anything, I need to do.

I have my '75 on jack stands. I popped the t-tops when I jacked it up (they are in place, just unlatched). The doors were closed. Without thinking yesterday, I opened the driver's door to get something out. Door didn't open smoothly, but did come open without much trouble. I immediately realized my mistake and tried to close it. Latch no longer lines up and it's stuck open. I have the rear suspension in pieces while working on it this winter, so I can't immediately lower the car and see if everything is OK. I just pulled the battery so it wouldn't run down. I've looked at the frame and crossmembers, don't see anything structurally concerning. Anything else I need to worry about? If my frame is no good anymore, I'd rather find out now before I dump more money into the suspension.

edit: May 2021
in case anyone finds this topic having the same problem. I was on the jack stands for 5 months due to a series of issues. I had some sleepless nights worrying about the flexed body. I’m happy to report that when I lowered it, it immediately flexed back. Hood, doors, t-tops all close/latch/unlatch. If you are in this situation, take a deep breath, have a beer, and don’t let it consume you! It will be fine.

 

When my brakes needed a complete (and I mean complete) overhaul, I put my 76 up on my quickjacks. The car was on them for about 5 weeks, the brakes were bad enough that I tried to fix, had to order more parts, moved forward, had to order more parts, times about 4. So, after a complete brake overhaul, my car was up on quickjacks for a while. I panicked when I opened the passenger door and it would not close, I posted here on the Corvette forum about it. Also, what really freaked me out was when I started the car on the quickjacks, just to run it a bit, and the motor fan would not spin! I was told NOT to take the t-tops out, which I luckily did not do, but these cars DO flex!
The good news is that when done with the brakes, I put her down and all back to normal....

 

It is good practice when lifting a C3 to crack open both doors and "pop" the hood

 

There is definitely flex when c3's are up the in air on stands. I noticed some door gap issues when I had my c3's in the air and a "sticky" door. Once they were back on the ground the gaps issues were gone and the door operated smoothly again. If it's still in the air, I'd open both doors if you can and pop the hood. I always removed t-tops for that kind of work also, but I tend to be over cautious.

 

Nothing to worry about as long as your frame is structurally sound.

 

I find all of this very interesting. back when I first purchased my 77 there was no Forum. or if there was I didn't know about it. I jacked it up the first day I owned it. have had it on jackstands time and again over the years. front only, rear only, on 4 stands all wheels off the ground. have taken T tops on and off. opened and closed doors. gotten in and out, all a thousand times or more. never had any issues of any kind. these things are built on a ladder style full frame. mine does seem to flex ever so slightly if I don't put a floor jack under the front crossmember. but not so as to miss alighn a door, hood or T top.

 

Whatever flexing goes on when up on jacks will go away when back on ground. Normal door gaps are wide enough to handle it. Nothing to worry about.

 

Maybe I'm doing something wrong, As I go south for the winter , like 8 months or more , I put my 80 on jack stands. I jack up 1 side at a time with the jack under the middle of the frame and place the jack stands on the frame just in back of the front wheel, and in front of the back wheel. Then go to the other side and do the same. Open doors with no problem , disconnect battery , shut the door , put on the car cover and say sea next summer.,

 

Anecdotally....
i never have issues glass tops , doors, starting, turning...but i have a 79..and quickjack.
i tried to find the poster who does frames..also facebook frame page to see what years may matter..but..my quick take..
- rusted or damaged..all bets off..
- around 77 on up...it seems no issues
edit- adding convertibles (which i assume is covered above past 77)

all assumes minimum centered 4 jacks..

 

I've had mine on stands for over a year. Doors open and close fine. I think it depends on where they are placed.

 

AND the body mounts/brackets are not rusted through. The body may flex enough to cause a stress crack in the paint....especially on a convertible.
I learned the hard way

There are some threads about placing jack stands in specific areas under a car to prevent major flexing.

 

The national tire chain that I went to when they put on new tires opened the hood and doors when it was on the lift. Also I heard some loud popping sounds when I lifted the car on one side once so I am never going to do that again. I suspect there is quite a bit of flex especially on the older convertible cars.

 

Live and learn. I replaced the rear shocks on my low mileage, but 15 year old 2001 Camaro Convertible. Lucky for me, that I had the top down, because once I had the rear end on jack stands, the doors didn’t want to open. I think most convertible body’s will flex when they are on floor jacks, and when cars are 40-50 years old, it’s more pronounced.

 

If the frame is solid and the body mounts are in good shape, nothing really moves.......my 72' doesn't move around at all, no matter how I jack it up.
I have a bit of a pickle on my car as it has a front monoleaf.......jacking it up via the front crossmember is not an option........I jack it up behind the wheel but do not like how far back those lift points are so after it is lifted, I put two tall *** HD jackstands under the front sway bar links......this is a great place to set them, and they are out of the way of suspension and the engine area underneath. This is the same area that shows above in the manual up front. The lift points in the rear leave a LOT of weight to hang out front of the jackstand......I had a 76' here a few years back that you could physically see the front end droop.....didn't attempt to open the doors LOL!

Jebby

 

Same here. I've owned my '76 since 1988. Countless times on 4 jack stands and sometimes 3-4 months. T-tops and doors open/close just fine as if it were sitting on the ground. The frames are very solid on these cars for the weight they are supporting. If my car flexed like some have described, I would be a bit concerned and would endeavor to find the cause. Its not the frame unless it has weakened from corrosion.

 

I put my front stands either under sway bar bushings or to the frame right behind front wheels. Back stands go to the frame right ahead of the rear wheels. I have a good solid frame and good body mounts. Never had an issue.

 

I had my 71 on 3 ton jack stands for over a year with no issues. I did a complete drive train and engine rebuild and a 5 speed. The rear passenger side was about the thickness of a matchbook off / above the stand. It was the same when I went to take it off the stands.

Same with my 72. It was on the stands for 4 months - doors opened and closed - no issues. Did the trailing arms and all universals.. and all rubber bushings in the front end , they were original and starting to crack.

 

I should have noted that when I did my brakes, she was up on quickjacks the entire time. I've always thought she was remarkably rust free, but hearing how many others don't even have slight flex issues makes me wonder!