One thing I noticed was there was no shims between the body and frame on any of the mounts? The number 4 had a square washer on the passenger side. Unless they are stuck to the body side, I haven't lifted it up yet and looked from underneath. Is this normal to have zero shims?

I know the rear gap at the door was wider at top than at the bottom before the lift so I assume a shim or two at number 4 during the rebuild should fix that but since its going on a new powdercoated frame is there any procedure in the assembly manual showing how they figured where to shim and how many. I can assume # 1 and # 4 are shimmed to even the door gaps but what about #2 and #3?

Thanks!

 

Hi Pm,
It would be very unusual for a car to have no shims.
While people may now use shims at various mounts to set door gaps, that wasn't ever the case in St.Louis.
The frame was 'measured' in a jig and a shim count was written on the frame rail. The intent was to bring all the body mount surfaces to a specification
This was done while the frame was upside down and was before the frame was 'introduced' to body that would sit on it.
The frame was turned over and started on down the line. Someone then 'read' the shim count at each location and taped the proper number of shims at each mount.
After the body was lowered on to the frame there was no means to pick it back up to add shims.
Regards,
Alan

Note frame is upside down and gauge used to determine the number of shims required. Also note this is a 73+ photo because there appears to be rubber body mounts next to the gauge and shims.

 

It is not normal that there were no shims...But I have had several where they were only two or three for the entire car. It has everything to do with how the mount perches were welded to the frame.

#1 and #4 body mount points are not always used to do as you thought. #4 on a convertible can really aid in changing the rear door gap like you mentioned so you are correct there. BUT...The amount of shims or lack of shims in #3 can change how you add or not add shims at the #4 areas. #2 mount area can sometimes be used to pull down or raise up the hinge post area.

When I am putting the body on a new frame like you are doing..I already know what I am up against due to I have checked the levelness of the body mounts with a laser pointer to get me in the 'ball park' so I have an idea of how many shims in what spot I will need right off the bat.
BEFORE I started using this method....Ii did it the old way of setting the body down and using 'stuff'..I could figure out what shims it would need.

When I attach the body I then got to the body height that GM outlines and get it close to that or within specs....then I also check to make sure ALL bumper brackets will go back in and allow the bumpers to be bolted back up.

Keep in mind that it can happen that even though all went well...when you drive it with someone in the passenger seat of the car...your floorboard can tap on the driveshaft area and make a sound. This has happened to me but usually on the 1963-1967 model years. BUT...it still can happen on your year model ESPECIALLY if the car has had a bit of damage history.

DUB

 

Thanks Alan and Dub, again I appreciate your time and input. I was wondering what people did when they had rotted out frames or were using a new frame. I assume the specs for the frame are in the assembly manual? If not does anyone have them? I can shoot it with a laser line and measure the rest off the highest or lowest and get the difference in height.

As far as body damage I cant find any signs of damage or any serious damage. All the brackets for the bumpers and supports were there, even for the ones for the front chrome bumper even though they removed it. Now I dont know if they were the original or not but it looks like someone just spent a ton of money, probably in the early 70's, to make their car look like a 73 or whatever. The door panels are stamped originals even though they are covered in white leather. I have to remove them and see what's underneath. No rust at all which for a 48 year car from NY is an absolute miricale in itself!

 

Hi Pm,
There are dimensions for the top surface of the body mounts shown in the Chassis Service Manual. But to use them I believe you need to have a 'surface plate' on which to position the frame so your measurements are consistent and accurate.

When folks are starting with a frame with unknown shim counts they often put 3 shims on each mount. Then install the body and add or remove shims as needed to properly support the body, and on convertibles, adjust the rear door gaps.
Regards,
Alan

 

Thanks Alan. I was thinking of that fact. Outside of having a frame table to work on and being the frame is already a roller I was going to lift the frame and level off of jack stands and work from there.

Question with the three shims per mount. What am I looking for when I sit the body to check besides door gaps? Also what does adding/removing from each particular mount do? I said before I assumed #4 raised/lowered the rear. #1 is too close to do much with the front doo gap but might affect height of fender? #2 & 3?

Thanks a million!!

 

FOR WHAT THIS IS WORTH:

I WOULD NOT raise the frame in order to get the body shimmed. Keep it on the ground with the tires aired up. Using jack stands and not placing them in the CORRECT AREA. (which most people do incorrectly) will basically be causing you to be adjusting your body to a frame that is NOT correct.

Keeping it on the ground is a REAL WORLD scenario...because the car is always going to be driven with all four tires on the ground----right????

NOW...you can take and use whatever advice is given to you.... but I can say that when I am installing a body on a new frame or a frame that has been damaged and straightened back to GM specs. I DO NOT start with 3 shims at each mount point.

Body mount areas #1,#2 and #3 are all made into the ROCKER CHANNEL. #4 as you know is all by itself.

#2 and #3 are level with each other IN the rocker channel.
#1 as you can see is up higher than the level plane of #2 and #3.

SO..using simple math and some straight edges and measuring tools...you can determine what the different between the level plane of #2 & 3# is to #1,

Then you check that information to your frame because they are not all the same. Which is why on some cars...like yours was ...may NOT need shims because when you are trying to achieve the body height measurements that are outlined in the assembly manual.

Keep mind that this is also in a 'perfect world' and that was when the body was new and never had any stress on it.

I know some people just do not believe m me when I comment on it BUT the gusset that is riveted/bonded to the top of the hinge post area at top where your top hood surround gets bonded to a the cowl plenum CAN loosen due to improper jack stand supporting techniques and it causes this area to fatigue.

SO knowing that #1 is so close to #2 body mount...they are still independent and DEPENDING on whatever issues a particular car has...shimming them in a different manner that would NOT be normally used has been done due to issues that have to be adjusted for.

These cars are old and who really knows what type of abuse they have seen...and trying to meet a specific criteria that will make everyone comment "Good job"...really is foolish for you to try to do. You have to get it set to what it tell you it needs and forget on how you get there. I do not start a thread every day on what I do at my shop mainly because how I get to the end of the repair or project and it being right....some people would not understand because they are not right beside me seeing what I am dealing with.

Just do not do like some people do (or try not to) where they get overwhelmed and have 8 shims here and there and still do not have it right. This is mainly due to they often times allow their head to get in the way and make it much more complicated than it really is.

With you having it on the ground it is easy to raise one side at a time and install or remove shims wherever you put them. I simply raise it by the edge of the steel rocker channel and using my floor jack or jacks. YES I know...when you go to tighten the #3 body mount bolts with the wheel/tires on...it can be a bit of fun...but not impossible. Obviously...make sure that when you go to raise it..the bolts on the other side are really loose but still in there so the body can tilt. Sometimes I will remove #4 body bolt entirely when doing this....it all depends on how high I need to get it to get to what ever body mount I am dealing with. Common sense applies.

DUB

 

DUB, that is ALL VERY GOOD ADVICE.

 

Thanks Dub. I appreciate your time and knowledge. I was wondering why people start with three shims on each and why not start at zero and see how it sits, then start adding for the least amount possible.

When sitting the body on the frame are you adding shims to make up gaps to the particular mount or are you looking at anything else on the body (door gaps, etc) to add shims to fix? I like your idea of measuring with tires on the floor. I'm sure my floor isn't level and will compare floor to how the frame sits. I'm curious if the 69 vette frame was designed to sit level with same size tires? Dub you've been a great help with all the questions I think about as I plan and slowly move forward.

 

Hi Pm,
The only time shims at the front crossmember between the core support and crossmember, and at the #1 body mounts, can affect the door gaps is if the front clip isn't completely/properly bonded to the cowl.

When you put the body in place you'll look for obvious gaps between the shim and body surface.
You then need to decide if the gap is caused by a lack of shims at that mount or too many shims at the opposite mount.

Remember the body is ridged so you use the shims to stop from 'rocking' on the mounts.
Regards,
Alan

It's fairly easy to see if another shim is needed.

 

That was actually the only place I did find shims was at the core support.

 

Hi Pm,
They were used there on some cars.
My point was that if the body is assembled properly the shims tip the entire body, not just the clip.
If they only tip the clip, it's loose at the cowl… if you think about it it has to be.
Regards,
Alan

 

You need to look at the assembly manual in the section that gives the measurements...and where to measure. They have it outlined.

You need to get to the point that when you begin to get the height measurements to where they fall within specs...you are good to go. And...like I previously wrote...that is being in a PERFECT WORLD scenario and does not always apply.

Trying to get the body back on and RIGHT the first time when it is a new frame and you do not have an engine in it or interior or the body close to curb weight....The chances that you may need to do some FINE TUNING before you go and paint it may be highly likely (if painting ti is the next step)...or you may not need to anything further to it at all. Sorry...there is NO crystal clear answer to this scenario.

IF you look at about every GM photo of Corvettes....from 1963 to current...the rear is slightly higher than the front for reason. Due to a transverse rear leaf spring...when you leave from a dead stop..the rear end will squat ..and then the car is basically level when going done the road. IF you get the car level when it is sitting there still...then when you take off..the nose of the car will be higher..WHICH IS NOT GOOD.

To prove it in much simpler terms or method. AUTOMATIC TRANSMISSION EQUIPPED CORVETTES WORK BEST TO PROVE THIS> Crank your engine...put your foot on the brake and hold it good and put the car in gear and lightly press the gas pedal a little bit and the rear will squat. NOT LIABLE for any idiot who runs their car into a wall or off a cliff because they do not possess or use common sense when attempting this. Just saying.

Like I wrote...do not let this get to complicated. It is not like you have to have the car on a concrete pad that passes NASA specifications for perfect level. It's ALL about math and being able to read a measuring tape or instrument.,...because I have set bodies up in peoples garages where the floor had a bad slope to it....when the car was put out on level ground it was spot on.

I AM NOT trying to make light of getting the body back on correctly and secure...but worrying about NUMBERS and getting them in specs may drive oyu to the 'funny farm' if oyu let it get to that point.

I can take a tape measure or a tram gauge and begin measuring out areas on just about anybodies Corvette and I WILL find inconsistencies. It is what it is.. But IF those inconsistencies are not able to be readily seen by the naked eye...then why worry about it.

AS for the shim (if it has one) that goes between the front crossmember and the radiator support. It has to do with fan clearance to the fan shroud. Instead of loosening up the front crossmember side brackets and adjusting them...it is easier to loosen up the two bolts that hold the radiator support to the crossmember and slide a shim in and the problem is fixed. NOT all Corvettes with chrome bumpers have this shim. Because if you also stop and think about it....the perches that hold your motor mounts can be off.

I know on many of the frames that I stretch the cradles back out and get correct...I am watchful of the motor mount perch area when the pulling is being done and use a bracket to keep those two points correctly spaced....if the engine is out of the frame.

Hopefully this helped in some of your questions and if not ...keep asking so it can help you.

DUB