Hello everyone,
Recently new to this forum as I never knew this existed and was directed here for help through another group. I need some help and knowledge if anyone can help. A little backstory, working on a 1977 that my dad and I were restoring(frame off) which he passed away in 2017 and I kind of lost interest in at that point as it was our project. Car is/was at 80% complete at the time of his passing and I'm starting to get the itch to finish this off for him. This is where I need some help/knowledge. First off, I need to pick someone's brain that has shimmed a body after putting it back down on the frame. Unfortunately the body was pulled off the frame around 2007 and the knowledge of the old shims has since been lost so I would be staring from scratch. I thought it was going to be as easy as to put the body back on and just put shimms where the gaps are, but have just learned the shims will determine door gaps. Is there anyone that can message me as to help me with this process?

Thanks so much and really enjoying everyone's posts.

 

Place a golf ball size lump of modeling clay inside a sandwich bag and tape it over each of the mounts. Lower the body onto the frame until you just make contact with the first of the eight mount locations. Stop. Look at the gaps at the other 7 locations. You want to be sure you are lowering the body as evenly as possible at this point where you avoid overloading any one of the clay bags.

Continue lowering until the full weight of the body is on the frame. Extra word of caution - pay attention to the front of the car while you are lowering as you want to be sure you have the surround/front fender fiberglass in a “neutral” load condition. In other words, if you have the body mounts assembled but the front support pieces - core support/front crossmember and bumper brackets improperly located - you will induce stress in the fiberglass and end up with issues such as cracking.

After the car has settled, check your door gaps and window/window seal interfaces. Check how the doors open and close. Measure the gaps and fit/fair. Take notes.

Raise the body and carefully remove the clay. Measure the clay and build up your initial shim stacks. Keep track of each so you don’t mix them up. Create a diagram of the 8 stacks and each height. Position the shim stacks and lower the body. Verify you have the front supports such that the surround/fenders are in a “neutral” load status. Shim/adjust the brackets as necessary to achieve.

Check the door gaps, window/seal interface, fit/fair and compare the measurements to your first set. Take notes.

The #2 and #3 mounts should be viewed as a set, with the #4 an “independent”. Your door gap to front fender is controlled by adjustments to the hinges. Do not consider addressing any bad door/front fender gap by playing with body mount shims. Some will claim they can change that gap by raising/lowering the surround/fender mount points but what they are doing is over stressing the fiberglass to cowl bond. Don’t do that. Use your door shims to optimize the door/front fender gap.

I like to use the #2 mounts as my reference plane. Prop up a 2x4 against the frame in the plane of these mounts. Measure the distance between the wood and the bottom of the birdcage rail. Add shims as needed to level the body left to right.

Next, assess the #3 mounts. Note that the door/rear fender gap is influenced by adjusting the shims at the #3 and #4 mounts. Keep in mind, however, that you can introduce unwanted stress in the aft body by placing too many or too few shims at these locations. Proceed first by filling out any gaps in the #3 mounts, then assess the door gaps and shim the #4 as necessary, avoiding too few or too many.

Check the difference in height of the body, between left and right, at the aft crossmember. Record the measurement. Hopefully, there will be no major difference but if there is, you can add the same number of shims to the #3 and #4 on the “low” side to address.

Fill out the gaps in the #1 mounts as the last step.

You need to think of all of these process steps as part of an interconnected system. Go slow, take notes, observe, think.

This procedure has worked for me many time but is a guideline, not an absolute. Others will weigh in on their process which may be different than mine.

One final point - these cars were mass produced and the overall quality wasn’t like cars built today. You likely will need to accept some compromises so don’t seek perfection.

 

@Melting Slicks

Thank you for the reply. A lot of useful information but from your answer I think I need to provide a little more detail and context. The car was completely striped when we separated the body from frame. No bumper supports front and back, no core support, no hood, no doors, no interior, etc., etc. If you can name it, it was taken off the car. We actually set the body back down on the frame back in 2016. None of the bolts were tightened down and the bolts just started a few threads into each mount. The car is still sitting like this to this day and all equipment used to lift and drop body has since been removed, so I don't think the clay baggies are an option. I will also note that I was afraid new rubber bushings would deteriorate like the old ones, so I went the poly route with new bushings. I can only imagine that over the last 8 years, that the body has settled onto all 8 mounts evenly(maybe not) but the #4 mounts are tight and I don't believe that to be the case when the body went back on. Due to this I imagine the rear gaps in the door are going to be wide. So since none of the mounts have any shims I cannot take away from mount #3 and assume my only option to be to add to #4.
Another thing to note is that when the body went back down onto the frame, it went on top of an entire rolling chasis, so everything on the chasis is alreadly installed. We actually did the engine break in while the frame was not under the car. I honestly wasnt even aware of the door gaps being affected by the shims so i actually hooked up and bled the brakes so im going to have to take something loose there in order to lift the body high enough again to place shims.
Lastly, will the shimming of the mounts affect hood, ot t-top alignment? Want to make sure all the bases are covered as I want to make this a 1 time process. Thanks!

 

Hood and T top alignment, no.
I replaced all my body mounts on my 77 a little over a year ago. Yes my right thumb has finally healed, thank you.
I don't necessarily agree with the above statement of treating number 2 and 3 mounts as being the same.
Certainly wasn't true in my case.
Everyone says count the shims and replace with same number. That's not correct either. As the new replacement shims are thinner than the original shims.
Not that this matters to you.
On my 77. I found 1 shim at number 1 front Left. No shim at number 1 Right.
2 shims at both number 2's. 3 shims at number 3 Left ,2 at number 3 Right. 4 at both number 4's.
when you lift these body's they bend like a banana. Set it down and wait a good day before checking anything.
I would start with numbers like I had found on my car. And adjust from there. Take your time. let it rest into place after each adjustment.
I thought I would add, your correct those rubber body mounts only last 45 years. Poly should crumble in half that time. Rubber will dampen vibration much, much better than poly.
It's your car of course.

 

The bare body weighs about 800 lbs so you only need to raise is a couple of inches to get some working room. A couple of floor jacks and a couple of 2x6s will easily accommodate that. Yes, you will have to re-bleed the brakes but that you already know how to do.

I’d be concerned about the front fiberglass not being supported for such a long time. Fiberglass is subject to a phenomena known as cold flow so the front clip is a bit lower today than it was in 2016. As you reinstall the front brackets, etc. avoid, as much a possible, “forcing” the fiberglass to line up, particularly at the “point” of the hood.

The T-tops should not be affected by the process because their mount points are determined by the birdcage which, unless rusted badly, will not move.

 

Thanks everyone for all the great information. However, I think I'm questioning more now than I was before making this post. Since I need to lift the body again to shim the car(Albeit just a few inches this time) I'm now questioning to putting rubber bushings in instead of the poly. I never realized when starting this process that the body mounts would affect the door alignment or I would have left the doors on the car. This process has been years in the making and I'm not looking forward to hanging these doors due to how long it's been. The body and frame were separated for roughly 6 years and now the body has been sitting back on the frame for roughly 6 years. Over that 12 year period I'm going to hate to see how badly aligned everything is. In all honesty now I'm wishing I could just pay someone to align the body. I live in one of the US major cities so I'm thinking it may be a good idea to search out some local corvette clubs as well.

Another thing that I'm now questioning are the front door gaps. When I started this process I always hated the gaps at the A pillars as I thought they were extremely wide and now reading one of the posts, it sounds like this gap isn't really fixable with the mounts so it's probably going to need material added when it's time to go off to paint.

 

Poor gaps at the front of the doors is really common with these cars. They rolled out of the factory this way.
So, yes can be a pain to fix properly.
Me, I'd do this myself as I'm to poor to even consider paying someone else to do a job this big. And I would be concerned someone else wouldn't take the time to do it correctly. It's been apart this many years, what's a couple more months?

 

I would definitely recommend rubber mounts.

Take a deep breath, you can do this! Map out a plan, get everything ready (including your notebook!). We will guide you through the rough spots. Get ready to post pics because we all want to see what you are seeing!