Shimming the C2 body to frame
11-24-2009, 04:42 PM
#1
Le Mans Master
Thread Starter
Shimming the C2 body to frame
I am working out issues on my C2 created by the previous owner or restorer.Most have been cured.
My rear drivers quarter,bumper,light etc... sits visibly higher than the corresponding passenger rear section. I have checked the frame on a machine. It's within specs. My fully restored suspension is also within specs. I am also having an issue with driver door alignment at the latch. From all measurments the drivers rear section is a 1/4 inch to 1/3 inch too high.
I feel it was improperly shimmed. One indicator was at the grommets under the floor pan on the frame crossmember. The drivers side has 1/4+ inch shim and the pass side has just the rubber disc. I have not checked the other points. I am hoping I will find similar shims on the driver rear frame mount and the one in front of the rear drivers wheel.
Any advice on how this should be solved, would be helpful. I have never dealt with shimiing or setting the body on frame.
My rear drivers quarter,bumper,light etc... sits visibly higher than the corresponding passenger rear section. I have checked the frame on a machine. It's within specs. My fully restored suspension is also within specs. I am also having an issue with driver door alignment at the latch. From all measurments the drivers rear section is a 1/4 inch to 1/3 inch too high.
I feel it was improperly shimmed. One indicator was at the grommets under the floor pan on the frame crossmember. The drivers side has 1/4+ inch shim and the pass side has just the rubber disc. I have not checked the other points. I am hoping I will find similar shims on the driver rear frame mount and the one in front of the rear drivers wheel.
Any advice on how this should be solved, would be helpful. I have never dealt with shimiing or setting the body on frame.
11-24-2009, 06:40 PM
#2
Race Director
How are the door gaps on the driver side - even top to bottom? Also how are the top of door to top of rear and front fenders - level with each other? Sounds like you may indeed have too many shims in the rear on the driver side, but changing the shims on a convertible can markedly affect the door fit. If your door gaps are pretty uniform top to bottom, my guess is you might want to remove a couple shims out of both rearmost body mounts on the driver side. that might bring the rear fender down evenly and maybe not affect the door gaps too much. Odds are you will have to pull the door panel also and do some adjusting of the door after re-working the shims. But - there are no sure fire answers to your question. You will just have to experiment with it and see what happens.
11-24-2009, 11:48 PM
#3
Le Mans Master
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St. Jude Donor '12
I had a similar problem... had to start from scratch. I started by putting the two rubber inboard cushions and flat washers at the front of rear end, then started with about 3 shims at each body mount, the body will tell you whether it is too much or not enough... went from back to front, checking door gaps and checked door closure fit, fender to hood alignment, and front end preload at the radiator support. Body lines need to be looked at along the way. After I tightened everything down, it was solid and true. Took about 2 1/2 hours but worked out fine for me. Probably lots of other ways.
11-25-2009, 06:21 AM
#4
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Shimming a C2 Body
This information comes from the April, 2000 issue of Corvette Fever in the Resto Clinic section authored by Noland Adams. 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.
Cheers Ray
This information comes from the April, 2000 issue of Corvette Fever in the Resto Clinic section authored by Noland Adams. 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.
Cheers Ray
11-25-2009, 01:41 PM
#5
Le Mans Master
Thread Starter
Shimming a C2 Body
This information comes from the April, 2000 issue of Corvette Fever in the Resto Clinic section authored by Noland Adams. 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.
Cheers Ray
This information comes from the April, 2000 issue of Corvette Fever in the Resto Clinic section authored by Noland Adams. 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.
Cheers Ray
02-03-2010, 03:40 PM
#8
Drifting
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02-06-2010, 08:51 AM
#9
Burning Brakes
I need a little clarification… I’m done replacing the mounts on my ’66 convertible and I’m about to start aligning everything. I have questions on the #1 mount (the one in front of the doors at the base of the firewall - referred to as #2 mount in above post). There are shims above and below what I think is the birdcage rail. Looks like the upper bracket is attached to the firewall. Where is a safe place to lift to add/replace shims above the birdcage? And what alignment does that effect on the car?
Joe
Joe
02-06-2010, 10:12 AM
#10
Race Director
If you have some sort of overhead lift - engine hoist or car lift, you can remove the hood latch receivers and secure a lift bracket to them. Using several large boards below the foot box floor and a floor jack will also work. Use the widest boards you have and will fit and jack just enough to replace the shims and isolators.
I don't know what purpose there would be in shims on the topside of the body mount bracket. There should just be a washer under the bolt head I believe. The mounts do secure to the firewall and birdcage structure.
As far as what effect it will have on panel alignment - think of the length of the car as a 2x4 with four points of support spread along it's length (5 for a convertible).
On the second point (body mount) - if you shim the mount up it will arch the board upwards between the two adjacent mounts - opening the front door gap at the top. It may also change the rear door gap at the top, but to a much lesser extent.
If you shim it down and tighten the body bolts, it will arch the center downward between the two adjacent mounts - closing up the front of door and vent frame gap at the top. It may also change the rear door gap at the top slightly.
One qualifier is that the front clip of the Corvette is very flexible. It may work better to adjust door gaps by very slightly shiming up or down the convertible-only mount under the door threshold plate. The convertible guys on here can better answer that.
I don't know what purpose there would be in shims on the topside of the body mount bracket. There should just be a washer under the bolt head I believe. The mounts do secure to the firewall and birdcage structure.
As far as what effect it will have on panel alignment - think of the length of the car as a 2x4 with four points of support spread along it's length (5 for a convertible).
On the second point (body mount) - if you shim the mount up it will arch the board upwards between the two adjacent mounts - opening the front door gap at the top. It may also change the rear door gap at the top, but to a much lesser extent.
If you shim it down and tighten the body bolts, it will arch the center downward between the two adjacent mounts - closing up the front of door and vent frame gap at the top. It may also change the rear door gap at the top slightly.
One qualifier is that the front clip of the Corvette is very flexible. It may work better to adjust door gaps by very slightly shiming up or down the convertible-only mount under the door threshold plate. The convertible guys on here can better answer that.
02-06-2010, 10:32 AM
#11
Burning Brakes
Thanks Dan, the shims in question are little horseshoe shims between the top bracket (attached to the firewall) and the top of the birdcage rail. The larger square shims (with bent tips) go between the birdcage rail and the frame mount. There’s a diagram in the assembly manual that shows what I’m trying to explain.
I was going to leave the little shims alone but someone used some shims with a tab on them that partly blocks the drain hole behind the mount.
I understand the large shims but I can’t get my mind around what the little shims do so I may just try to gently lift that side of the body from the floorpan to slide the tab away from the drain hole. I’ll find out how I’m doing once I start adjusting my gaps.
Thanks for the help… expect more questions shortly....
Joe
I was going to leave the little shims alone but someone used some shims with a tab on them that partly blocks the drain hole behind the mount.
I understand the large shims but I can’t get my mind around what the little shims do so I may just try to gently lift that side of the body from the floorpan to slide the tab away from the drain hole. I’ll find out how I’m doing once I start adjusting my gaps.
Thanks for the help… expect more questions shortly....
Joe
02-06-2010, 01:29 PM
#12
Team Owner
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Thanks Dan, the shims in question are little horseshoe shims between the top bracket (attached to the firewall) and the top of the birdcage rail. The larger square shims (with bent tips) go between the birdcage rail and the frame mount. There’s a diagram in the assembly manual that shows what I’m trying to explain.
I was going to leave the little shims alone but someone used some shims with a tab on them that partly blocks the drain hole behind the mount.
I understand the large shims but I can’t get my mind around what the little shims do so I may just try to gently lift that side of the body from the floorpan to slide the tab away from the drain hole. I’ll find out how I’m doing once I start adjusting my gaps.
Joe
I was going to leave the little shims alone but someone used some shims with a tab on them that partly blocks the drain hole behind the mount.
I understand the large shims but I can’t get my mind around what the little shims do so I may just try to gently lift that side of the body from the floorpan to slide the tab away from the drain hole. I’ll find out how I’m doing once I start adjusting my gaps.
Joe
02-06-2010, 04:47 PM
#13
Burning Brakes
Those shims (shown in the Assembly Manual in UPC 1Asm, sheet G1, item #2) were installed on an "as required" basis when the cowl assembly was bonded to the birdcage, after the birdcage was bonded to the underbody, to fill any gap that occurred at that location (so the lower portion of the cowl panel wasn't stressed when the #1 body mount bolt was torqued). If the cowl/firewall hasn't been separated from the birdcage, there's no reason to change the thickness of that shim pack; if you need to change the shims, replace with the same total thickness.
That makes sense now. thanks John. When I tried to put a little upward force on the floorpan nothing was moving so I stopped. I was able to swing the tab blocking the drain hole out of the way so all is well.As I've mentioned before, this forum rocks!! Thanks guys.
Joe
02-20-2014, 08:39 PM
#14
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body shims
I have a similar problem all my door gap and locks work great but my rear d/s is almost 1/2inch higher than the p/s. Ir really became noticeable in the paint shop because nothing is on the car. I saw a lot more shims on the d/s than the p/s my painter suggested to take two out of d/s and move them to p/s. just don't know how to lift the body enough in rear to get the shims out. Any ideas anyone?
