Hi all,

Say I need to get my 68 up in the air for some long overdue maintenance/repairs.

I’ve been through old Forum posts, a lot of them, and I know there are multiple perspectives on how to support
the car in the air whilst working on it.

some say you have to provide supplemental support for the front end, some say open the doors and unlatch the T tops,
others say don’t do anything just use Jack stands where the Factory Jacking points are and leave the doors/ T tops alone,

im estimating the car will be in the air a week, maybe two at best.

looking for real world advice from fellas that have had them airborne for a couple weeks and the method(s) they have used.

 

I have had my 77 up on Quickjacks for MONTHS........nothing happens. I open door, close doors. If something is going wrong.....I don't know what it is????

 

What's wrong with leaving a Vette supported by the frame with the wheels of the ground? I leave my Vettes up on a lift, supported in 4 places on the frame rails, for months at a time. The doors open, the doors close, everything works, nothing gets damaged... what's the problem? It's just a plain ol' Chevy with a kit car body on it. Raise it up and don't worry about it.

 

It is a matter of moment arm affect on the body forward of the doors which is dependent on the placement of the jackstands.

In this view, the poles supporting the body are located, left to right, at the #4, #3, #1 body mounts and the front, just forward of the hood opening. Note that the #2 mount is approximately 1 foot to the left of the #1 mount.

Most folks will place jackstands under the area between the #1 and #2 mounts and near the #3 mount points. If you envision a jackstand under the #1 mount, notice that the entire weight of the engine (and everything forward of that point) is being exerted on that jackstand. All of that weight acts to bend the frame at the point (called the joint axis) where the jackstand is located. Since the body is bolted to the frame, it will also have the same bending force applied. Fiberglass is, of course, not steel so the risk of stress-induced cracks will be increased and that increased stress is focused on the surround and front fenders. Door opening/closing is unaffected in this case.

The same argument is applicable when pulling the body off the frame. You need to support the nose with a strap back to the lift point to avoid stressing the surround and front fenders.

If you are going to be having all 4 wheels off the ground for any amount of time, it is best to support the front in the general area shown by the picture.

 

When I lived in Wisconsin, I put mine on jackstands every winter. And let it sit like that on average 6 months at a time. Never an issue.
I've done extensive work to my car on 2 or 4 jackstands more times than I can remember, running the engine, getting in and out of it, sometimes with the tops on. Sometimes with the tops off.
This car is built on a full frame! If your frame flexes that much by lifting it, what's going on while driving on a rough road?
Just pick it up. Jackstands at the front of the frame just before it bends upwards. And in the rear in front of the rear tire right at the end of the straight section.
DONE.

 

When the car is supported with the jackstands behind the front wheels......they have to be positioned where the frame is not kicked up.......a good foot behind the front wheel......now look at the engine in the above photo....it is literally hanging off the jackstands out front of everything.......plus all of the weight of the wheels, suspension.....etc........probably a thousand pounds of stuff hanging out front.....now add that to the fact that there are a LOT of rusty birdcages and old shitty body mounts on these cars now (even 30 years ago)....and you can see how the front end weight could literally pull and stretch a weak birdcage/frame.......and this is where you get all of the fuss about open doors and unlatched T-tops......add that to the overwrought Vette "enthusiasts" who make a big deal about **** that doesn't matter and this is where all the confusion starts.......
I personally support the front of my Vette at the two sway bar mounts up front with tall *** jackstand.......this is not only a better place to support it but jackstands behind the front wheel are in the freakin way of anything you try to do.......but, I have supported it and other Vette's behind the front wheel too when the need arises......with no issues.......

Jebby

 

Putting supports up front, as Jebby said, certainly would better support the frame. Not a bad idea....whether its required or not.

 

Materials aren’t perfectly rigid. Apply enough force and the frames will bend. Why invite a potential problem when it is so easy to take the extra step to eliminate the chance?

To each their own.

 

My solution.
Not completely finished but you get the idea.
I built this as I can't work on the car in a container, screw all those other quick jacks, floor jack, kwik lift.
I had the kwik lift for awhile, to old for that BS now.


Lift in lowered position, = low roof

Lift goes up = roof goes up. Plenty of light, vehicles covered for elements

 

Good analysis. I've been using a two post lift with four support points front and back along the rails. T-tops are fastened and on. The frame definitely bends, the door gaps widen and lately the bonding along the left front fender at the door jamb has separated some. All that stuff in front is having its moment.

 

I see what you did there.

I have the same issue on my 2-post lift. I have a 6ft tall “jackstand” that is used at the rear to stabilize any vehicle you are lifting, but I may have to get a 2nd one to give the nose a bit of support as well. I don’t have it on the lift for long periods, though, so it does go back where it belongs when back on the wheels.

 

My 68 vert is up in the air on a quick jack lift most of the winter. Its a vert so it sags A LOT at the doors. The gaps grow almost a half inch. If I open the doors I dont slam them shut.....and when it hits the ground in the spring everything is fine...been that way for atleast 6 years...its s 68, they dont have the rear kickups so they are a bit flexier than the 69 and newer years


ive jacked it up from the sides at just one point or jacked the front up from one A arm to get it high enough for a jack stand to then get the jack on the other A arm....never an issue.....what the hell are you gonna do if you get a flat....these are vehicles, not toys...it takes a lot to do any damage to them

 

People are just paranoid. The engine is only 24" forward of where the frame starts bending in. That's almost exactly the same distance it is on my A-body. So the heaviest component isn't really cantilevered that far away. People forget how far back the engine sits in these cars - its BEHIND the front wheels. Yes the nose is long, but that doesn't mean the weight is at the tip.

As for comments about the frame bending - you can support the entire car on a single point and won't permanently bend the frame with a static loading. These things are designed for dynamic loads which FAR exceed anything you could possibly do just letting it sit. A good pothole will put more stress on the frame than letting it sit on a jack stand.

Finally; your car has been lifted between the wheels before. No service center was supporting the nose of these things when they were new. They treated them like cars and lifted them as the factory recommended.

 

No paranoia involved. Just respecting physics. As I mentioned before, to each their own.

 

I've done the beam calcs. I'm quite confident the original engineers did too. Physics says its fine. But yes, you are welcome to take as many unnecessary steps as you so wish. Your car, your effort, I really don't care what you do. Just letting others know it is completely and wholly unnecessary.

 

Care to share that body of work? Am very interested in knowing how you addressed the effect of frame corrosion.

 

You can use the new wall thickness...it isn't rocket science. This is stuff any second year engineering student can do.

Again, the frame is designed for dynamic loading. Its designed for braking, cornering, shock, vibe, fatigue. Sitting at 1G is nothing. The margins are ridiculous sitting on a jack because that loading is literally nothing to the frame. If your frame were going to fail sitting on a jack, it wouldn't be road worthy.

 

I work with a building full of engineers, bioloists and chemists...lots of big brains and super smart folks....about zero common sense in the lot of them....we literally had to go label every door push or pull.
You should see the younger ones designing ramps and braces on their computers....their computers cant tell them what a truss is so they just keep increasing the wall thickness at the joints.

Basic math doesnt exist either. The machinist has to keep explaining that if they want a 12×6 piece machined it has to be bigger than 12x6 for the lathe to attach to it or for the mill to mill the ends square.

I laugh now when some of you guys start over thinking this stuff.

 

It’s not “over-thinking”, it’s thinking, then taking prudent, sensible, actions accordingly.

You can laugh all you want as we live (thankfully) in a free country but it doesn’t serve those who don’t understand and who reach out to the forum for advice. This is not a case of who is right and who is wrong, it is simply a collection of experience and opinions. I am a mechanical engineer so I think in technical terms, shaped in part by 50+ years of ownership experience with C1, C2, and C3s.

We all know the adage about opinions. No problem at all expressing one’s opinion in the forum but we are all better off avoiding trying to argue who’s opinion is the better choice. That decision is up to the person seeking the advice.

 

Its not just you...its most of the engineering world...
Dont take it so personal....most smart people realize they dont have commomn sense.....Some of the younger engineers are really good at recognizing that and laughing at themselves...