OK guys - so after months of waiting, I finally got the body back on the frame of my ‘81. In doing so, things don’t really seem right. In the interest of not bombarding this thread with a million photos, here’s an Imgur link with all the photos. I can get more tonight if you guys want to see other parts of the car.

Issues:

• (Most alarming) Passenger-side #4 mount - the reinforcement is not resting on the rubber. It’s in the air about an inch.
• (Second-most alarming) Passenger-side control arm contacts the inner fender liner, while driver-side seems perfectly centered.
• Passenger-side headlight is noticeably higher than driver-side (look at distance from frame)
• There appears to be more space between the fender and the top of the wheel on the driver-side than on the passenger-side.
• Door gaps seem to be off - they’re wider at the top than on the bottom (on both sides).

I’ve checked all the body mounts and they all look like they’re in the right place. The nipples are in the holes on the #2 and #3 mounts on both sides.

The bolts are all hand-tight right now, I haven’t torqued them yet, so I’m sure things will change when I do that. But I have to imagine most of this issue comes from not having the right number of spacers. I only used one on each of the mounts, as I didn’t know exactly where to put them. At this point, I can figure out how many spacers to use by trial and error, but I don’t know exactly which mounts they should be put on to resolve the issue.

Also, if you guys see something else that may be causing this issue, please let me know.

Thanks in advance!

 

First question would be what were the original shim counts at each body mount during disassembly?

 

I didn’t even think to count at the time, unfortunately. I figured the Factory Assembly Manual would’ve told me how many to use, but it just says “as needed”.

 

Is the body sitting flat on #2 and #3 body mounts?
Could any of the #2 or #3 body mount inner metal sleeves or cushion flanges, be hung up on the body?
Could anything else be hung up?
Are you utilizing the alignment holes in the door sills to chassis (frame) holes?

My shims and aluminum body mounts (71) were dust when I pulled it all apart so I had to shim from scratch. Its not too hard, its just a process that includes door alignment.

Cheers,
Richard

 

I didn’t not utilize the alignment holes, I didn’t know about them until after I had put the body back on. The mounts looks good, I don’t think it’s getting hung up on anything.

My mounts were absolutely toast as well, so I may also have to shim from scratch.

 

If you had the doors off, did you scribe or otherwise locate their correct position? If not, they may be poorly adjusted for now.

 

I never took the doors off. I’m honestly less worried about the alignment of the doors, and more worried about the #4 body mounts and the passenger upper control arm.

 

Put the car on jackstands that are high enough for you to easily manuver under it.
Level the car frame across the front jackstands.
Level the frame across thr rear jackstands?
Add shims between the jackstand a d the frame on th LOW SIDE IN THE FRONT.
DO THE SAME TO THE REAR LOW JACKSTAND.
Now level the driver frame rail fro t to rear addind shims as needed.
Do the same to the passenger frame rail.

The frame is now level...find a frame measurement diagram for your year/model.
Take measurements/hand-draw a diagram to see iif the vrame is bent or warped.

Let us know what you discover...post a pic of your handrawn diagram with your measurements.

Expert forum members can advise you what to do if the frame measurements are. Out of tolerance.

It's better to find out now if your frame is bent or Straight.

 

Start with putting 3 or 4 shims at each body location. Add or subtract as needed so the body to frame sit properly.
Remember the body is the closer tolerance part of the 2 the frame is variable of the 2 parts.

For your other question.

Once you get the shims figured out.

Have you tightened all the a-arm bolts and rear spring bolt to factory specs. If so loosen them as they were finished torqued after the full weight or the body was on the Chassis. The corvette will sit up higher till all the weight is there plus movement of it. You have also reduced the weight on the nose with your LS engine. Also are you using rubber or Poly bushing?

 

Good idea.

I’m not following.

I have tightened everything to factory spec. Are you saying I should loosen everything, let it settle, and then retighten everything to factory spec? Should I do this with the car on the ground? Also, do the rear springs bolts even have a factory spec? I thought you just raised a lowered them to adjust the height of the car - I didn’t realize there was an actual torque spec.

Also, in case it matters, the rear springs bolts is now composite, it’s not stock. And the car needs an alignment, so the shims are totally out of wack. The A-arm shims I simply put what I thought would be right and then torqued it down, figuring I’d bring it to a shop to have an alignment before driving it. For the trailing arms, I didn’t even add the shims, nor did I torque the trailing arm bolts down - again figuring I’d take it to a shop to handle that. Everything else should have been torqued to spec before the body was put back on. Rear strut bars are torqued to spec, but I haven’t adjusted the camber yet.

Poly suspension and engine/trans mount bushings, but rubber body mounts.

 

OK first thing first;
1. do not worry about headlights for now since they are attached to the body and can be adjusted later.
2. check to make sure the frame is sitting on level ground.
3. verify all tires have equal pressure.
4. verify the front and rear springs are equally adjusted (front springs sitting in springs pockets)
5. once the above is verified then check the alignment holes body to frame. Those holes(4) are located under sill plate moldings and may have an orange plug in them.
6. you can adjust the body to the frame for side to side using a drift pin or a long round pry bar.
7. once body is sitting square or perpendicular to the frame you can do some quick measurements to check height of the body and frame to the ground
8. measure the frame from ground up using 6 points, two at the front of frame(bracket bolt holes or heads will work) measure the center section of frame using 4 locations (under rocker moldings there should be the slots) measure rear section using two locations either bumper bracket holes or bolt heads will work.
9. compare all the side to side(horizontal) measurements. Any deviation more than the recommended height of maximum number shims used needs to be addressed.
10. measure the body from the ground up using 6 points, usually the top of wheel openings and bumper attachment locations. Keep in mind guys have spent a lot of time and effort trying get these cars the sit level due to production or prior repair variables.
11. if all checks out you may have to shim body to frame as needed.

Hope this provides some insight.

 

This is great information, I’ll definitely do this.

That said, to your point about guys spending lots of time getting the cars level…how important is it that the car sits exactly level? Like, obviously the photo of my #4 bolt is egregious and needs to be addressed, as does the A-arm contacting the inner fender liner. But outside of that, will small variances (a missing shim or two) cause problems?

My biggest concern is that I don’t want to make the car to be unsafe.

 

The frame of all corvettes back then were not of a very tight tolerance as they were welded. There were variations to them depending if the welder was hot or cold welder the frame would be inconsistent. But the body was in a body jig as it was assembled and was closer to spec each time then the frame.

Your a-arms and the 4 spring center bolts weather original or composite should be loose till the body is complete and completely installed before torquing them. Plus move the car around to have it completely settled.

At the factory they were able to preload the suspension to a set figure and torque the a-arm and rear spring bolts. We do not have that capability.

The frame at the shim install point at the factory. They had a machine they called the spider. With the frame level on the conveyor the spider would be lowered to a datum point above the frame. At each body mount point would a tool would be inserted between the body mount and the spider legs. This tool had multiple steps to it the amount of steps it would go in. Indicated how many shims at each locations. See photo.





It would be critical to have the frame level to start. If it is not then you do not have a good starting point to add shims as the body is lowered to the frame.

 

Ahhh you meant the bolts on the center plate that mount it to the bottom of the diff. I thought you meant the rear spring bolts at each end of the leaf spring.

When I get home today, I’ll loosen up the A-arm and leaf spring bolts and let the car settle a bit before trying to add any shims.

Should I wait until most of the weight is back on the car before torquing those bolts down again? The only weight on the frame right now is basically just the engine/trans and the body. There’s nothing else in the engine bay, no gas tank yet, not even seats in the interior.

 

Also looking at your photos you should install the radiator core support. As that will help stabilize the nose of your Corvette. Along with the frame section that the core support sits on.


Yes loosen all of them now. When I say everything should be in the car gas tank, interior, engine compartment. All the weight you can get in it plus more if you can plus even drive it a few hundred feet to make it settle. We have added sandbag to help lower a car. Poly bushings in most cases do not settle as well as rubber.

 

Very very interesting. OK will do!

 

As other have said. You need to start over.

1. Remove the body add core support before lifting
2. Level frame on jack stands side to side front to back and add the front core support frame section
3. Remove tires
4. Add the 3 or 4 shims at each body mount
5. Then lower body to frame using alignment holes
6. Add or remove shims as needed
7. Once everything lines up add bolts and tighten body mounts

 

That sucks, okay will do. Also, what do you mean by “core support”?


Edit: Oh you mean the radiator core support? That hasn’t been on the frame in months - should I be adding that before dropping the body back on?

 

I believe the manufacturing variables are what can cause these vehicles to set a little off even after complete rebuilds with new parts. A couple of theories that I have are related to things like the steering column, steering box, brake control parts(booster,m cylinder) and battery located of the left side of the car opposed the rt side in an air conditioning equipped you have ac compressor and heater box. Non ac in theory would be lighter on the rt side even with the slight drivetrain offset. While this is just a guess I would think 1.5 to 1.75 inches difference side to side or corner to corner would be somewhat normal (if anybody knows please chime in).

As far as I can see the inner fender should not rest against the upper control arm. There are two to three possible causes if it wasn't like that before.
1. the inner fender was improperly installed.
2 the most likely case is that the front end has sagged down and can be corrected by lifting up the effected side and adjusting the rebar/frame extension. The front can drop a little bit and you will never see it in relation to the doors. A wheel opening measurement is recommended.
3. I would rule out that the body(front end) isn't setting to far over or forward on the effected side.

All of this of course is assuming the frame has not been damaged.

 

"All of this of course is assuming the frame has not been damaged. "IF you take your time you can level the frame in 2 hours...not only will you be able to determine if the frame is O.K........

You can also take measurements of the wheel well arches-to-the-floor and write them down to help you LEVEL the body WITH the frame mounts to determine how many shims you need on each body mount

You can also measure spring SAG to the floor to determine if one of the coil springs is bad.

There are other things you can mesaure....may as well kill 5 or 6 birds with one stone.

The only exception would be to set the car back down on level concrete after all the bugs are worked out.

The FINAL body to frame leveling with shims should be done with the full car weight on the wheels/wheels on the concrete...
it makes a huge difference in all the gaps looking nice....

There's alot of important information in this thread which will make a very safe car....all well worth the effort.