Ok all you big block guys(I don't remember this being an issue with my small block)
When I have my car up on stands, with the front ones right under the frame where the front door meets the front fender, the frame seems to flex alot when I let her down. The stands make contact with the frame, then it gets lower and lower. The rear will lft up a little I guess due to changing the balance point, but just a bit.
Is that safe? Am I doing damage to the car, or frame? My front sheetmetal is pretty much all on except for the inner fenderwells for now. Am I losing some structural strength without those in place?
Is there anything i can do to fix this, other then putting something under the tires so they take all the weight?
Thanks again, I'm propably just being over cautious.

I notice this with my SBC w/air. I recently had it the air with and w/o metal inner fender with no difference in amount of flex.

BTW, my body and core support bushings are shot. What condition are yours in?

Both of my SBC do it. It is really bad if the car is on a 4 point lift. The doors on the 2 door won't shut easily and the fan hits the shroud, once on the ground everything is fine again. It has been like this for as long as I can remember.

The doors on the 2 door won't shut easily

I chipped the paint on my door:mad:

I always leave a note taped on the door when it is on stands..."DON"T OPEN!"

It was a lot worse on my 'Camino before I replaced the body mounts.

I swear, the body is STIFFER than the frame. A tremendous amount of structural integrity is supplied TO the frame BY the body. Keep in mind that I've got a fully-boxed frame under my 'Camino; it's probably worse with the open-section frame used by the non-convertibles and non-'Caminos.

Coupling the two (body and frame) together properly with fresh mounts, bolts, washers, etc. makes a BIG difference--although you may still have some amount of flex when the vehicle is jacked up.

I chipped the paint on my door:mad:

I always leave a note taped on the door when it is on stands..."DON"T OPEN!"

A word to the wise is sufficient. Anytime that you jack a big block (and maybe a SB too) behind the wheel well, the frame is going to flex and the doors are not going to clear the back of the fenders. Even with the boxed frame on an Elky or convertible. Take Matt's advice and keep the doors closed or put a jack under the frame cross member.

Schurkey is correct.

I have all poly in my Elco, a decent body structure, and get a lot of flex when I lift it with a floor jack, both front and rear.

You can see everything moving if you're observant.

Makes me think again about the 572 waiting to go in... that frame is a real flexi-flyer.

The poly bushings made a HUGE difference, but metal still bends. The roll bar structure is probably the single biggest contributor to the very good handling of my car on the road.

I wish someone made a modern frame that would accept stock suspension parts. I don't really want to run C4 Corvette and 9" or whatever. I really love my Global West and converging 4 link with modern geometry. Car handles really well.

Eric

My car is a convertible and everything is new and I have had mine jacked up in all kinds of combinations and my frame does not flex.
Now my car being a convertible has a boxed frame.

A word to the wise is sufficient. Anytime that you jack a big block (and maybe a SB too) behind the wheel well, the frame is going to flex and the doors are not going to clear the back of the fenders. Even with the boxed frame on an Elky or convertible. Take Matt's advice and keep the doors closed or put a jack under the frame cross member.

I made the mistake of opening the passenger door on my 66SS while swapping wheels and tires and put a nice long chip in the front of the door and the back of the fender. Going to be an expensive repair once I get around to that.:mad:

so basically this is normal? Just don't open the door!

The doors on my 70 won't open if it's up on a 2 post lift. If opening the door while it's on stands is necessary, put the stands under the frot lower control arms to distribute the weight more evenly.
This is a major problem on unibody cars...like my 69 Charger. Even with jackstands under the control arms, the doors won't open.

My 70 does a lot of flexing too in the front part of the frame, and yes, unfortunately, I chipped the paint on one of my doors too. I happen to have al new body mounts, but they're the rubber ones. I've been considering the possibility of fabricating some 1.5" DOM tubing into a shape that would bring it from one frame rail to the next (passenger side to the drivers side I mean) and arcing over the bell housing right inbetween the back of the engine block and the firewall, and welding it to each frame rail. But I'm not sure if doing that would take up too much room back there and make it next to impossible to get to the top bell housing bolts in case of a transmission overhaul. What do you guys think? I've been considering this because I don't ever plan on installing a 12 point cage which has the strut tubes in the front going through the firewall.

I was wondering the same thing when I put mine on stands.

Would it be worse to only set the front or only the rear on jack stands and leave the other end of the car on its wheels?

I've made a habit of putting a floor jack under the front crossmember when the front is on jackstands. I jack it up just enough to take some flex out of the frame but not enough to take all the load off the jackstands. That way I don't have to worry about opening the doors. Safer too; I don't trust just (one pair) jackstands when I'm under a car.

so basically this is normal? Just don't open the door!

If you must have the door open, I also put a thick blanket on the rocker to keep the door open an inch or 2. Just remember to disconnect the battery or pull the dome bulb.

I'm not looking forward to replacing my body and core support bushings this winter.

Mine still does it even after I replace all of the bushings. The interior light comes on sometimes even with the door closed. This especially happens when on a lift.

I've made a habit of putting a floor jack under the front crossmember when the front is on jackstands. I jack it up just enough to take some flex out of the frame but not enough to take all the load off the jackstands. That way I don't have to worry about opening the doors. Safer too; I don't trust just (one pair) jackstands when I'm under a car.

I'm with Von on this one, unless I need access to the oil pan or something in the middle of the car I jack it up under the front crossmember then place the jackstands and lower it till the frame just starts to put pressure on the stands.. This way the weight is equally distributed between the three points..

And to answer the question, YES, it is normal for the front to sag when it's supported only with jackstands behind the front tires..

MOST cars do flex during jacking, driving, turning, going over obstacles or when parking the car on an uneven surface.
Pickup trucks particularly do this. Just sit in the bed of a pickup when someone is driving and observe the gap between the rear of the cab and the front of the bed.
When a body such as a 2dr hard top or conv vs a 2dr or 4dr post (really noticeable with a 4dr hard top) is driving, turning or going over irregular surfaces (ie railroad track at an angle), you can watch the gap between the door and the body and observe flexing.
Soooooooooooooooo, yes, these Chevelles do flex when jacked and placed on stands. If you need to have the car jacked and on stands so that the body doesn't flex and cause a problem with opening/closing the doors, place the stands under the front A-frames and the rear axle housing----------------------------the places where the cars weight is supported when on the ground. :thumbsup:
My 56 Corvette REALLY flexes when the hard top is removed!!! And the early Vettes had an I-beam X-member in the center of the frame, plus each frame rail is boxed the full length!!!

Same story here - both doors rub the fenders when the car is resting on jack stands behind the front tires. This is with new polyurethane body mount bushings all around. I've made the habit of lifting the front by the engine crossmember and keeping the jack there to reduce front-end flexing. I've also had good success jacking up the lower control arms if lifting only one side.

Someday I'll get around to boxing the center of the frame to help combat this sagging effect. If I had the $15K I'd replace the frame with a Roadster Shop full chassis:
http://rsperformanceconcepts.com/products/chassis/chevelle/

I've never seen anything like this but is there a type of jack stand made that cradles the tire? I usually place some 6 X 6 wooden posts under all four or two wheels ( depending ) and then chalk at least two wheels. It keeps the car level and doesn't create unusual stress points but I realize lumber is not the best thing for supporting a vehicle. I'm not completely sold on the safety of a typical jackstand.

My car has been on jackstands for sometime due to my rear axle rebuild has turned into a frame on restoration. I also jacked the body up one side at a time to replace the body bushings. Never had any problem with opening or closing the doors, hood or trunk. Here is a pic of her up on the stands.

with the doghouse off my 65 while removing drivetrain, you could jack the front crossmember and watch the distributor move closer and closer to the firewall. I have a pretty decent original frame, new body bushings and bolts. I don't mess with the doors when I am jacking the car, unless I have 4 stands under the car, right by each wheel.

When we have these discussions about a car not setting level, I really believe it is because years of driving and hard torquing have put a bit of a permanent twist in the frame. This seems very possible to me. These frames are over 40 years old and have had some serious motor torquing.
surely after 40 years the frame takes a little "set".

I always place my jack stands on the frame , over the sway bar mount.

You think the A body's stretch, try a corvette. The shop manual for my 70 says to open the doors and the hood and release the T-tops before it goes on the lift. I guess this is to prevent the fiberglass from stressing.

As for my chevelle, the frame is currently bolted to the wall to make more room in the shop and it hangs there nice and straight :hurray:

On my ElCamino the doors also get harder to open and close when its on the lift.I guess its body bushings for me too.

Almost every newer car I have flexes some amount too, it's normal. On the wife's 2003 VW GTI the doors catch a little when I have the front on stands to change the oil. This issue is not unique to these old cars nor to cars with separate frames.

My '85 MR2 is the stiffest car I've ever seen. It doesn't seem to flex at all, at least at the door frames, regardless of where I lift it. But then it is pretty small and doesn't weigh much. The Prelude doesn't flex much either, but it does a little at the doors if I lift it at the very front. The old '69 Chevy pick up doesn't flex within the cab, but you can see the flex between the cab and the box pretty readily. The Chevelles flex quite a bit. Actually, the a-body frame was design TO flex, especially at the kickup by the firewall, which made them ride smoother. Handling wasn't much of a priority!

Actually, the a-body frame was design TO flex, especially at the kickup by the firewall, which made them ride smoother. Handling wasn't much of a priority!That's interesting Rich. I wonder if because of this^, if they might therefore also be prone to permanent frame twist between the front frame crossmember and the firewall from dragstrip use with high power/high torque engines under the hood (such as 700+HP) if 12 point cages aren't used which have the front strut bars included to stiffen the front of the car. I'm thinking of the tremendous force that's put on the drivers side motormount from the engine block tugging on it from the torque of a hefty big block drag race engine.

I once saw a 66 malibu on a 2 post lift. In the air the inside light would be on, down on the ground the light was off. The doors were closed! The frame appeared to be solid.

That's interesting Rich. I wonder if because of this^, if they might therefore also be prone to permanent frame twist between the front frame crossmember and the firewall from dragstrip use with high power/high torque engines under the hood (such as 700+HP) if 12 point cages aren't used which have the front strut bars included to stiffen the front of the car. I'm thinking of the tremendous force that's put on the drivers side motormount from the engine block tugging on it from the torque of a hefty big block drag race engine.

As I recall how it was explained by John DeLorean in an article about the Tempest/LeMans/GTO the intended flex was from end to end, not in twisting if that makes sense. He said the front portion of the frame which holds the engine and front suspension was intended to flex slightly up and down with respect to the rear 2/3 of the car. He said this was a BENEFIT to handling. :clonk: He must have been fairly convincing since the author of the article went along with his comments and didn't point out the inherent contradiction of a flexing chassis benefiting road grip and handling in general.

Bottom line, the a-body was designed to be a basic car with a generally good ride sufficient to please the average GM customer and as such it was a solid design for everyday drivers but not without some issues when put into a performance handling perspective. Pontiac, Buick and Oldsmobile did a LOT more to enhance chassis stiffness and handling characteristics in their performance a-bodies than Chevy ever did, at least in the 64-67 versions. The Z16 was probably the only performance oriented Chevelle that seriously took on the task of noticeably improving handling, braking and chassis stiffness. Overall it was unfortunately dramatically limited by the tire technology available at the time.

and I thought I did something wrong on reassembly:confused:.noticed mine flexing and my core support actually shifted a bit.glad I noticed befor shutting hood.next build will get a boxed frame
eric:beers:

My 72 did the same thing. A little scary. I put the stands under the front sway bar mounts

.next build will get a boxed frame
eric:beers:That might help a little, but it won't eliminate frame flex completely. I have a boxed frame as well as other mods done to the frame, and it still flexes in the front. I think a 12 point roll cage where you have the two strut bars through the firewall and under the hood is likely the best way and maybe even the only way to eliminate frame flex completely.

my 70 el camino flexes quite a bit while on stands as well, and it is a 350 SB