C1 Shim Markings on Frame

[Sheldon S.]

I can,t find any information on whether C1,s had markings on the frame in crayon identifying how many shims there were at each body mount like C2,s and C3,s. If there were was, is it done in white crayon and any pics would be terrific. I searched archives but didn't,t find anything.

Thanks
Sheldon

[Chris S.]

Re: C1 Shim Markings on Frame

There was not
The rubber shim and metal shim were taped to the frame
Chris

[Jack M.]

Re: C1 Shim Markings on Frame

Herez an example from a 1961 Corvette factory body drop:

1961-Corvette-Body-Drop-1.jpg

1961-Corvette-Body-Drop-3.jpg

[Richard M.]

Re: C1 Shim Markings on Frame

Sheldon,

As Chris noted, no frame markings. On all of the 56-62 body-offs I've assisted or done over the years, I typically photographed and took notes on shim counts. I've seen some interesting shim stacks over the years. For example, below is a '59 I restored, being the first time its body was separated from the frame. It had quite a variation of shims at the respective locations. I took a count of each and measured them stacked up so that when I replaced them it got me close to original stack heights.

Here is some reference imagery with some additional jargon you may want to encompass before your first body-off restoration.

Video of lift for fun.....

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Static shot moments after the lift.
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Note that these shim stacks hardly ever followed AIM protocol, meaning some locations had cushions and metal stacked in any order, unlike the AIM protocol of locating them stacked, from frame mount as pad, then metal shims above, with a note stating the metal shim "As Required". This was hardly followed in my experiences. Many locations had the metal shim on the frame first, then the pad. AIM shows pad on frame with metal shims above toward the body. Below you'll see them in alternate stacks. Many on this car had metal shim on frame, then pads above. Some had shim "sandwiches" with chaotic combinations of pads and metal stacks.

Here you can see many different stacks.
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Some original masking tape remains.
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Also note these 2 rubber rectangular pads here(3706913). Thes pads were installed at random locations, hardly ever positioned where the AIM states to locate them. I'd think this also was a "As Required" process at the assembly plant body-drop line as well, even though the AIM makes no mention of that.
P2030063.jpg

At body drop time, I typically had the shim stacks set in place and taped down, but once the body was down I carefully looked at all of them for signs of accuracy, meaning if I saw gaps or not, and if it appeared there was too much pressure at specific locations.

I'd then take a long crowbar(padded) and wedged it between body and frame to see if I had adequate pressure or not. I also checked for lateral alignment of the body to frame as there is a substantial amount of "twist" that can happen because of the inherent play for the bolts in the large size of the holes in the body and frame mounts. This is important for later alignment of the side to side radiator support to wheel openings, all bumpers, shifter-to-console opening, etc.

I would have the engine, transmission, shifter and driveline installed on the frame. I would check all items for lateral alignment before bolting the body down, just snug enough to keep it locked down, but ready to adjust if needed later when installing other items.

I once got a '60 "finish the restoration task", and the freshly painted body was already bolted on the fully restored frame, tightly. On the 56-60, it is VERY important to have the height of the radiator support with respect to the frame measurement accurately positioned. If not, much later in the assembly process you would have a tough time locating and properly installing the engine "Fan Shroud".

On these years, the fan shroud has specific mount locations to the radiator support, then flanges down to the frame horns with 1/4-20 bolts. Also ensure before body drop that those 1/4-20 welded threaded square-nuts inside the frame are solid and clean. Same goes for the anti-roll bar weld nuts inside the frame horns. You don't want to try replacing those or bubba-fixing them with a double nut later.

If the body height is not set properly at the core support, particularly if it's too low, the fan shroud cannot be installed without altering the holes on both sides of the vertical mounts on the shroud. If the body is too high, you can get away with adding some washers at the frame, but either way it's not the prefered result.

On the '60 above, I had to loosen all 10 body mount bolts. Working alone, this is a pain. I then had to remove the 4 bolts at the forward cabin locations and kept adding shims until I got the fan shroud properly lined up to the verticals of the radiator support and the lower mounts to the frame horns.

The reason I mention all this is because the C1 body drop and shim process may appear pretty straightforward, but it can certainly get very complicated later if you don't check lateral alignment and core support height.

Rich

[Chris S.]

Re: C1 Shim Markings on Frame

additionally the "kits" from supply houses are metal and cardboard
On the C1s I have never seen cardboard
All the mounts are a reinforced rubber material - looks like conveyor belt material or something similar
As far as the stacks I have seen them both ways - metal to the body and metal to the frame
When I place a body back on I start with one metal and one rubber at every location and shim from there after the doors are hung

Chris

[Richard M.]

Re: C1 Shim Markings on Frame

Here's the set of original shims from that '59. I separated 2 that were sandwiched together. Using a eye loop, I shot that piece of "material" sticking up(last 2 photos). It has signs of being a fiber of some type. These may be a rubberized cardboard.

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[Chris S.]

Re: C1 Shim Markings on Frame

I have some original early c1 shims I will add photos of

[Richard M.]

Re: C1 Shim Markings on Frame

I have some original early c1 shims I will add photos of

Yes I'm wondering if and when they changed from the rubber to this material on that '59.

What might help is if the part #'s changed from early C1 to later C1. I only go back to '57 AIM, but have a 1929 to 1959 P&A which I'll check later too.

Oh, and I may put a torch on one and do a sniff test.

Rich

[Sheldon S.]

Re: C1 Shim Markings on Frame

Thanks for all the info and great pictures
Sheldon

[Richard M.]

Re: C1 Shim Markings on Frame

Thanks for all the info and great pictures
Sheldon

Glad to.....

So, I cut a piece and burned it. It's paper based with no rubber, no smelly burning rubber aroma, just like cardboard burning.
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Here's the 1959 P&A below.
The 1957 AIM shows metal shim 366981, soft shim 378516. I'm thinking the 378516(soft shim) was not available in service, so it is difficult to determine the actual composition, other than my "burn & smell" test.

The 1959 AIM shows metal shim 366981 same as in 1957, but now the soft shim is 3751562. These were available in service as seen in the P&A below. But note it's description. It states rubber. But I proved this one car isn't rubber, it's cardboard. Likely a carryover from possible early rubber shims, 378516 shown for 1957, but not a service part at that time.

Also, in the P&A, I believe there are several typos related to shim sizes. The metal shim 366981 is NOT 3" long. It's only apx 2 1/4" long.
20240505_121101.jpg

[David B.]

Re: C1 Shim Markings on Frame

As indicated in '57 AIM section 1 sheet 1, body shim 3706913 is 3.25 x 1.26 x .25 thick. It has 5 grooves .06 deep with various widths of .19, .16 & .20. quality of rubber or synthetic material to have a tensile strength of 900 PSI min.. Elongation 300% min. Physical requirement
Durometer 40-50. compression set 50% Max.

[Richard M.]

Re: C1 Shim Markings on Frame

As indicated in '57 AIM section 1 sheet 1, body shim 3706913 is 3.25 x 1.26 x .25 thick. It has 5 grooves .06 deep with various widths of .19, .16 & .20. quality of rubber or synthetic material to have a tensile strength of 900 PSI min.. Elongation 300% min. Physical requirement
Durometer 40-50. compression set 50% Max.

David, Yes, those shims are those longer all rubber, top ribbed pads that get glued on the frame. These cushion the floor in several specified loccations.

Do you have anything on the 378516 mount shim?

Rich
P.S. I edited and added info in my earlier post.... Post#10

[David B.]

Re: C1 Shim Markings on Frame

Rich,
My files do show I have 378516 print. Now the hard part to locate where filed.

[Richard M.]

Re: C1 Shim Markings on Frame

Rich,
My files do show I have 378516 print. Now the hard part to locate where filed.

Great! Thanks David!

When you get time that's fine, no hurry as it's purely research effort now.

Rich

[Richard M.]

Re: C1 Shim Markings on Frame

Here is one of those 3706913 rubber shims. I believe original. I keep finding some sprinkled around here. Note the dimensions do match the print. Interesting the mount bolt shims don't match the P&A.

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