I recently bought a 1972 Corvette last week, and I also recently made a post about the frame flexing while the car is being jacked up. I was told 2 different things:

- It's normal
- It's indicative of a rusty frame/birdcage
I am not all that knowledgeable on what is deemed acceptable and what isn't, my car is very rust free, all 4 body mounts are very very clean, not even any surface rust in the #2 and #3 cavities, but after reading what I was told on here in regards to the frame flex... I have been stressing about it and double checking the frame for the supposed rust/damage that is causing this flexing and twisting. The frame itself has nothing more than a little surface rust... atleast... that is what I see on the outside. I took some photos of the rear kickup section of the frame, I have poked around with a screwdriver and found no soft spots. All seems solid.




This looks the same on the passenger side. I can't judge how good or bad this is. This is an un-restored car. I did see some more rust on the inside of the frame in some spots. Here is one spot I noticed and it looks like it's rusting in the seam where the metal is welded together.


The birdcage rocker channel on the passenger side has a fair amount of mild surface rust with some spots of more moderate surface rust towards the center, I believe that can be remedied with a little naval jelly and some undercoating but I'm primarily concerned about more damaging rust and rust in hard to reach areas (such as the trailing arm pockets and the inside of the frame). Is any of this anything to be concerned about and what can I do about it to get rid of it so my frame stays solid for years to come? Thanks in advance. Have a great night.

 

I think everyone in the other thread said it's pretty normal to see some flexing when jacking your car.
Just seems some flex more than others.
You have 8 body mounts. The ones exposed to the elements are the number 1 and 4 mounts.
About a year ago I replaced all of mine. My car is a later car with the rubber cushions that deteriorate with age. I found my numbers 2 and 3 on both sides to be in good condition. While my number 1's and 4's were in terrible condition.
If your concerned , check those!
put your finger inside the frame rails and feel for rust inside. Also feel how thick the steel is.
Pretty sure your just paranoid.

 

Where are you jacking from?
Are you using the factory designated locations?

Can you open and close your doors when up on jacks?

When I got my 82 several years ago, I read some strings where people warned to loosen the t-tops to prevent cracking due to flex when jacking. I could never find where this actually happened to anyone, but I succumbed to rumor and popped them open anyway. I figured no harm.

I now have a convertible. I only jack from where the manual says jack; however, if the car will stay elevated for a while, I place jackstands holding most of the weight and then I place several scissor jacks under the car at various locations pressured to support some weight. I like the scissor jacks because I can tension them just enough to hold some weight while keeping the bulk of the load on the jackstands.

Call me paranoid, but I feel the frame will be less stressed by spreading the load over more points.

 

the frame looks good! Check for cracked welds where the sidde rails are welded to the enngine crossmember.
Thre are kits you can buy of precut gussets-braces to make the frame stiffer. Just make sure the frame is level before welding the braces into place.

 

That frame is new looking....its normal for these things to flex....theres a lot of weight on it with very little support. Do not worry about it. My door gaps get huge when I lift mine on my quick jack

 

I maybe wrong but , in the pics , the trailing arm looks badly rusted . Why is a wire tie holding the E-Brake cable ?
Steven

 

I'm guessing it was rubbing a wider tire. If you look at the welded seem there would be rust there if it was in bad shape. That looks like surfacevrust where the bed liner came off or it's a puddle of dirt from a water stain. There is dirt under there. That frame looks like it's been garaged in Arizona it's entire life....

 

I will trade you frames right now and I will do all the work to get my hands on that frame..

 

Squirt some penetrating oil on that last pic..its nothing.....I got chunks falling off the inside of my frame and it's a garaged car but in new england....someday mine will need replacing....you are lucky to have a pristine frame

 

the picture you posted in my opinion look pretty good for the age of the vehicle.
Surface oxidation is expected on any exposed metal materials where an oil film has not been maintained.

I Would say something along the lines of that 'rusting' only generally raises an eye when it starts somewhere that should have painted protection, or when it noticeably begins to eat or deform component to where it may require replacement or maintenance.

Surface rust on a bolt for example is fine if it doesn't alter the strength of shape of the bolt and your ability to remove and replace that bolt.
Surface rust on suspension or chassis components should be fine if superficial, and has not eaten into the component, sometimes it can be difficult to tell. You may need to 'tap' or 'smack' or 'push' rusty spots to get a feel for how bad or deep. Mostly in the picture it all looks very solid to me.

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I am not an expert on your model vehicle frame. Nevertheless I have inspected thousands of various random vehicles over 25 years for maintenance and wear/tear and planned performance builds and corrected rust where needed by cutting/sanding/blasting/coating etc... and quite familiar with what I consider passable rust, well. I do not let anything rust because I cover everything as needed. I just mean for cars I see where people are asking whats normal. For example my rear upper control arms are coated in grease and because grease sticks dirt I wrapped them in protective sleeves to keep the grease and parts new inside. I am just giving an example of how you can prevent even superficial rust by planning for protection. There are some parts like differentials that seem to surface rust up no matter what you do. And some things like driveshafts that seem like rusting would be fine or normal but it really isn't and should be sanded cleaned painted and resolved. Yes I'm one of those people who knowingly greases up their brake rotors. Hell I even have a tube that allows oil vapors to splatter onto the compressor wheel of my turbocharger. Most people would say thats insane but actually its factory OEM methodology. People just dont know

 

I don't see anything in the pictures you posted that I would worry about, it looks better than about 80-90 percent of the unrestored cars I've seen over the years.

Corvette frames will flex, especially when being jacked up, many cars will. T-tops aren't as bad as convertibles because of the "T" bar tying the windshield frame to the Targa bar, but they still have some flex. All 68-69 Corvettes came with wedges on the door and lock pillar to keep the door gap in spec. In 70 they eliminated the wedges, but added a large chrome alignment pin and matching receiver to the door and lock pillar of all convertibles to combat the flexing. They no longer added anything to the doors of coupes after 69, but that doesn't mean they no longer flexed, it just means that the amount of flex that coupes endured was within what GM considered to be acceptable.