When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I will be installing a new, (reproduction), frame shortly and this presents a circumstance I have never before dealt with.
How do I shim the new frame, what is the base line?
I have noticed that the pictures in Nolands restoration guide show the shim marks on the frame long before the body drop, how was this done, how did they know how many shims were needed in each location?
I doubt if the bodies were so consistent that they measured frame inconsistencies and shimmed for that irregularity.
Where do I start. ?
As always all assistance will be greatly appreciated.
3X2, I think they used a jig to quickly determine the number of shims at each location and mark the number required on the chassis. JohnZ can tell us the truth. :)
I read a thread over on the C3 Forum on how to shim your body to a new frame. It was detailed and systematic, and the invidual seemed to know what he were doing. I don't know the date, but I believe it was about three months ago. Check the C3 archives. I made a copy, but I can't find it now.
There was a Noland Adams authored response in an old issue of Corvette Fever. I emailed the editor and asked for permission to pass the info on in an electronic form. I was asked to give credit and to also paraphrase the info. Here's a procedure for shimming a body when you don't know the original, factory shim count:
This information comes from the April, 2000 issue of Corvette Fever in the Resto Clinic section authored by Noland Adams. I have paraphrased the information and any spelling, grammar or technical errors are my own. The question that was answered by this info was from a gentleman that had purchased a '66 convertible. At the time of purchase, the body had been removed from the frame and the frame had been blasted and painted, any frame marks at the mounting points had not been noted and the shim counts had not been noted as well. In paraphrase form, here's the information about properly mounting and shimming the body.
There was a gauge used at the St. Louis assembly plant to measure variations in the frame. Color coded stripes were placed near each body mount to help figure out the final shim count for each body mount. These stripes were only a starting guideline. Due to inaccuracies in the gauge or variations in the body, shims were often added or subtracted as required. The gentleman with the above mentioned '66 simply lost his starting point.
The first thing to do is to identify the body mount locations. '64 and later convertibles have 10 body mounts, five per side. Coupes have four on each side, but the procedures are the same.
The front body mount (#1) is between the radiator support and the frame. The shims are welded in place at the factory and rarely need to be modified.
The second body mount (#2) is under the ends of the windshield. You reach this mount from under the hood - the left one is under the brake master cylinder, but a little more towards the rear and out side of the car.
The third mount (#3) is only for '64 to '75 convertibles and it's located under the sill plate.
The fourth mount (#4) is in the rear corner of the passenger compartment, hidden behind a metal rectangular cover in front of the rear tire.
The last mount (#5) is in the rear of the body and is the last mount to be shimmed and adjusted.
To mount the body to the frame, we are concerned with the adjustments to six body mounts. They are #2 left and right, #3 left and right and #4 left and right. Start with a minimum number of shims, which is either three or four at each mount. Hold them in place with masking tape and align them for the mounting holes. Lower the body onto the frame.
Install the body mount bolts, washers, shims, nuts, etc. on the six body mounts that surround the passenger compartment - left and right sides #2, #3 and #4. Correct placement for parts is shown in the Assembly Instruction Manual (AIM). AIM shows rough drawing and part numbers, but most body mount kits come with an instruction sheet.
Tighten the six body mount bolts to firm, just a little more than finger tight. Look closely at the shims at each of the six locations. The weight of the body should hold each stack of shims solidly in place. If any of the shims have spaces, remove the bolts and add shims as required. Replace the bolts and again firmly tighten all six bolts.
The bolts are slowly tightened until two things happen: the six bolts are evenly adjusted, but are all quite tight, and there are no gaps between the shims. These are the ideal body mounting conditions for the mounts around the passenger compartment.
The doors are installed next. Each door hinge has six bolts and there are a number of shims at each hinge, varying from none to six. Getting the doors adjusted can be rather difficult. There are two vertical gaps, one at the front of the door and one at the rear. The goal is to get both door gaps even. The front door gap is changed by adjusting the shims on the front mounts, #1 right and left, under the radiator support. Adding shims to mount #1 closes the front door gap at the top.
Each corner of the body is adjusted with more or fewer shims under the four corner body mounts. These are #1 left and right and #5 left and right. If the doors adjust properly, you're done. Some body work may be required for a perfect fit and you may have to adjust the doors a few more times.
If the body has to come off again for paint, the shims are already in place. You still need to adjust the doors after the body is placed back on the frame. Expect this whole procedure to take quite a bit of time.
Again, credit for this procedure should be given to Noland Adams. I just paraphrased it for this list.
Great to see your frame is rebuilt! Interesting to note you have a “late 68” frame with the 69 style braces at the rear kick ups. Perhaps the last 6 to 8 thousand cars got them. Very good to see the project coming along!
Great to see your frame is rebuilt! Interesting to note you have a “late 68” frame with the 69 style braces at the rear kick ups. Perhaps the last 6 to 8 thousand cars got them. Very good to see the project coming along!
It feels good to get something done on it for sure!! It is a later 68 frame (#20464) and as far as I know the 69 braces are original but I suppose someone could have added them along the way.
As for the body it was considered the most accurate of the 2 parts. The frame were accurate to a point but due to the welding process the heat produced would cause inconsistency. So at St. Louis they had what some call a spider it would be dropped to a predetermined datum point. A worker would slide a tool that had progressive steps each step would indicated the amount of shim to be placed at each body mount. There are many cars that may have no shims at 1 or more mount points.
As stated above yours will be a trial and error making adjustments to each mount with body lowered to the frame. If you know what your original shim counts were that could be a good starting point.
Designer Imagines A Corvette That Looks More Like a Corvette Than the Corvette
Slideshow: A Jaguar designer's personal project imagines what a modern front-engined Corvette might look like if Chevrolet revisited the golden age of the Stingray.
Mid Year Frame Shims, (new frame)
