I am doing some extended work on my 74 C3 and will have the car on jack stands for 3 months...do I need to open the doors and hood slightly?
I have heard that it helps to keep the body of the car from flexing, however, I really don't know so I'm asking the experts here! Thanks for your continued support and assistance!
BTW, IT'S A CONVERTIBLE (IF THAT MATTERS). Thanks so much

 

No need to do anything special as it'll just un-flex when you put it down onto the ground again.

 

Hi 74,
Convertibles tend to be a little more 'flexible' than coupes.
So I would leave the doors and hood closed.
If you're concerned you might consider using 6 jack stands rather than 4. (2 additional at the front frame extensions.)
Regards,
Alan

Perhaps at the location shown here… just to the rear of the sway bar mount.

 

As usual, Alan is correct and has awesome pics to prove it.

I had door issues with my convertible on just 4 stands, so I added two at the front to stop the droop and it worked great. Just remember to be careful how/where you jack it up. The middle of the front crossmember is thinner than most people realize. If you put a jack under there, be sure to have a block or something to distribute the load.

 

I hate to contradict the information provided BUT...this is no joke.

Here is a GOOD (really good) question to those who are looking at the diagram.

The jack stand points that are right near the number 3 body mount area (just in front of the rear tire). What do you think is going to happen to the rear body rearward from this fulcrum point when it is set on the jack stand. With the weight of the rear differential, suspension, fuel tank and so on. The door gap ( especially on a convertible) can or WILL widen....and it can be bad enough that it can not be repaired by setting it on the ground and 'unflexing' the frame' as some may think.

This comment is only because I have had to repair 'tweaked' or 'flexed' frames on convertibles that were incorrectly supported for a short length of time... and when the car was set on the ground..the door would not close and latch.

My philosophy is this.... regardless of any charts....because please also consider I work on Corvettes in all different grades of wear and tear. Pristine frames and some that are really rusty and questionable...but this method works on ALL of them.

We all know the car is supported by the wheel/tires..and they are connected to the control arms and trailing arms...so...like I do in my shop. I put the jack stands under the control arms in the front under the shock absorber...and then I put the jack stands under the wide part of the brake rotor where the parking brake shoes ride....so...the car does not know that is is not on then tires/wheels like it is normally. In some cases I will also put the jack stands under the wide area of the front rotor such as if it is in the paint booth being painted.

IF I am working on the suspension and I cannot put the jack stand under the wide area of the rotor due to it is going to be removed....or the tailing arms are coming out. Then while using a floor jack for center support..I place the jack stand up by the front sway bar n the front and then have super tall jacks stadn that allow me to conmtact teh rear crossmember for the differential.

When I am working on the car and my normal areas (under the rotor) can not be used. I do not 'dilly-dally' around when I have it supported while removing components. I get them out and when and if I am doing a total front end suspesnion tear out..I put the jack stands up in the pocket for the coil spring...and if the rear trailing arms and differential are out..the jack stands are on the crossmember for the differential mount area. These two locations are so close to where the contact patch of where the tires touch the ground..it would thus...logically be supporting it as if it were on the tires.

The chart above was probably a good thing back over 40 year ago when the cars did not have a lot of fatigue on the metal...but I know I would not do it that way.

If a person chooses to follow that chart like a 'bible' and disregard what I hoped to convey.... I hope it works for all of those use do it...especially those with convertibles....because this same subject has been discussed before...and after I mentioned this same thing.....a Corvette Forum member tried the GM way and came back and acknowledged that when he did it that way.....the door gap got really wide......but ....do as you choose. And IF you think that just because when you support it the GM way...do not be surprised that one day if the car is supported for a long time that you come out and find cracked fiberglass in the door jamb.

DUB

 

i would just add some under the rear suspension or use blocks to get to the furthest rear part of the frame.

 

DUB, This is excellent information. The next time you have a car up on stands, can you snap some clear photos, both from a slight distance and up close, so that we can visually see where you are placing the jack stands?
You do describe it very well, but a visual is always better.
Thanks, Greg

 

With appropriate "cushion" (rags or wood) can a person jack the rear up using the spring perch or diff cover in an attempt to jack up both sides of the car at once? Or is the "one side at a time" approach better?

 

Will do tomorrow..I may not have a car up in the air...but I will use a rotor on a jack stand to show where I set the jack stand which should be good enough.

I attempt to jack it up in the center of the differential area if I can....even if I have to drive the car up my custom made wood ramp gismo. That way it makes it easier for me to get my floor jack under the car.

I also try to lift from the center of the cradle in the front so both front tires go up at the same time. And for many of you who may be 'freaking out' by now and a 'purist'......I know what I am doing and I do not smash the underside of the cradle when I do this. I have been doing this long enough to really have a 'clue' by now on what to do.

The only time this changes is when the car has the high performance Vette Brakes & Products suspension under it. It makes it more challenging to raise up.

DUB

 

having owned a Corvette shop for many years myself, I am in total agreement

 

For those who need a photo.



As described.

DUB

 

Literally, a photo is worth one thousand words.
Thanks, Greg

 

****DISCLAIMER****
30+ years of doing it this way and NEVER had a Corvette fall. I will slide under one all day long that I set up like this and have no fears at all. BUT...I am not liable if someone decides to treat the car in an aggressive manner that something happens because they are not thinking clearly ( such as trying to install an engine when it is supported like this)....or set up the jack stands where they are only barley contacting the rotor. I am not liable of foolishness and lack of common sense.

I am glad it helped clear up any questions.

I can say...that when doing this and putting them under the rear rotor.s..and obviously you either have the lug nuts on to hold the rotor in place or they are still riveted on. When lowering the car...do it slowly and while applying pressure to your jack stands.... you will need to help them move/slide outwards a bit due to the rear suspension is settling. If you lower the car too much..the jack stands will start to tilt and get in a position that trying to get them to settle will be really hard to do.

And not need to freak out because you still have the floor jack under it. AND many times I put my jack stand on cardboard so they will slide easier. Once they are flat on the floor...all is good.

 

Good stuff. Dub, when you say you put jacks under the "rear cross-member for the differential". Is that possible with the half-shaft in place? Running from memory, I visualize the cross-member and half-shafts being aligned vertically. Please tell me I am wrong.

You also say you "jack it up in the center of the differential area if I [you] can". To be clear are you saying you place the floor jack under the differential housing?

Since my front cradle was bent by a former owner, can you elaborate a bit on how you raise the car from this point?

Thanks!

 

I will recommend you leave both doors and the hood ajar because when lifting the car the gaps between the panels can close and chip the paint.

 

Supporting it from the differential crossmember will depend on what year the Corvette is...so the 1980-1082 Corvettes with the aluminum differential may not be able to be supported that way....and exhaust is also a factor. On the cast iron differential the crossmember on the frame is not in line with the crossmember for the differential.

Some of what I write about will depend if the cars frame is being supported for months on end while serious repairs are being done and many components are off of the car...while...supporting it for a few hours or a week end...may require further investigation of the owner to find the best location to support it...and IF they are working on their own car...then taking the time to have special supports fabricated may be worth while instead of 'just trying to get by' and support it with what you have.

I come across so many Corvettes that are so different when it comes to the exhaust pipes that run under the differential. Sometimes I can not get my floor jack to catch where I want it. I prefer to try to catch on the strut rod bracket for the cast iron differentials if possible.,...but many times the exhaust has been 'fudged' with and I can't. Sometimes I try to get on the plate for the rear leaf spring...and that is a hit or miss situation also.

On the aluminum differentials Corvettes...I look and see if I am lucky enough to get on the strut rod bracket are if possible. Getting on the actual differential usually requires me to have already driven up on my wood blocks so the rear is already up about 3 inches....and that can allow me to get onto areas and raise the car.

On the super duper nice resort-mods I work on that are literally painted frames and polished exhaust and suspension, etc....I have to improvise and either use two floor jacks (one on each side a raise the car enough so I can get the wheels off and then I bolt on the thick aluminum adapters for aftermarket wheels I have and sue them as a jacking point...after making sure it lock down the rotor so they can not move...so this means I have numerous floor jacks and not just one.

So...it all boils down to looking at what you have and figuring out what you need to do or possibly have fabricated....because it can sometimes take me well over an hour to get one safely supported without damaging any paint or parts.

Sometimes I need to remove the rear 'Y' pipe for the exhaust.....or have to deal with exhaust that has been welded up and had to remove it from the exhaust manifolds or header collectors. So it all depends...because like I wrote in the beginning of this post...they can be different and what would work on your car may not work on another persons Corvette.

DUB

 

So let's throw this into the mix.

I've been considering a "Quik Jack" that engages the frame just in front of the rear kick up and then the front of the frame as it turns in before the front wheel.

My car is a vert so I am very interested.

 

Mine is a '69 Roadster. To your point about 'special supports', I've often thought about making some custom jigs to help with simultaneously lifting of the front and/or rear. When possible I use the wheel crib blocks that I built to make the car's resting as natural as possible. I built each of them as a two part assembly so I should consider building some alternate inserts that allow me to use them when one or more of the wheels are off the car.

 

To both of you...taking the time to figure out what you might need to do or fabricate is the first step. I am glad that you are both thinking and receptive to not just taking what is often times the 'given' on jacking and support locations for a Corvette...and not considering other possibilities and locations that protect you Corvette.

For what this is worth..and it is 'kinda' relative. I built a fixture to hold hoods for painting and repairs and I have different attachments that allow me to hold all of the hoods from 1963 to 1982. AND I have another fixture that I built so when I am painting the front fenders, headlight doors, bumper covers and hood for a 1997-2016 off of the car...it can hold them. So...fabricating as many fixtures or possibilities of interchange is something that I am all for doing.

DUB

 

http://theautodolly.com/5-bolt-roll-around/

I remember seeing these in a summit tool catalog but summit doesn't carry them any more. These would be a little more secure for those that want to put a stand under the rotor. With a little skill you could make something similar in a home garage pretty easy.