TRUNK LID FIT


Q:

I have a 1960 Corvette and I am having a problem with the trunk lid. This condition was not present prior to the frame-off build.  The leading (front) edge of the trunk stands up approximately one-half inch.  I have done all of the adjusting with the springs, but nothing I do seems to have any effect. If you can give me any help, I would greatly appreciate it.

A:

I read your question with great interest. While it is impossible for me to be certain of the diagnosis, I can probably bring a few things to light.


First, let me remind the readers that the trunk hinges on the first generation Corvettes are of a fairly complicated design. The hinge assembly that controls the trunk lid also controls the convertible top, or deck lid. These hinge assemblies incorporate a design that locks one lid while allowing the operation of the other. In this way, the two lids cannot be open at the same time, which would cause them to contact one another and cause damage to the painted finish.


If you open the trunk and remove the trunk divider cardboard, you can see into the hinge tower. Built into the hinge tower, you will see two sets of back-to-back hinges with interlocking linkage devices. These interlocks are designed to control the operation as I have explained above; keeping one lid closed while allowing the other to open. You will also see that there are two sets of springs. One pair is to help open and close the trunk lid, and the other pair controls the operation of the deck lid.


These hinges and springs are designed in an ingenious way. It helps to know that each pair of springs is able to do two entirely separate things.


First, they aid the owner in opening the lid by helping to lift some of its weight. This is accomplished by using energy that was stored in the spring the last time the lid was closed.


Secondly, they help to lock down the lid by pulling downward on the lid after it has been lowered about half way. This type of spring arrangement is commonly called an “Over center spring design.”

The best way to learn about this design is to operate one of these hinges with the lid removed. If you were to remove the trunk lid, and you were to try to operate the hinge arm by hand, you would be surprised at the power that is stored in the spring. The hinge arm would be difficult to lift from the closed position until it was about half way up, and then it would jump up with substantial force. That is the action of the arm going “over center.” In other words, the spring would cause the arm to stay in the middle of the arc all by itself, but, if you move it up a little off center, it would like to jump all the way up; and, conversely, if you were to move it down a little below center, it would jump down with considerable force.


The clutch pedal return spring works in the same way. It holds the clutch pedal up for you when you are not using it, and then, after you have pushed the pedal down about half way, it assists you in pushing the pedal down the rest of the way; thereby helping to overcome the tension of the springs inside of the clutch itself. You don’t usually feel the full motion of one of these spring assemblies because, when they are in service, the other components shroud the operation of the over center spring design. If you were to remove the clutch from your car and then push down on your clutch pedal, you would push against spring tension for approximately half the travel, and then the pedal would jump forcefully to the floor. You would then have to pry it up off of the floor. After lifting it about half way, it would jump up to the top of its travel because of the over center design.


How does all this relate to your problem with your trunk lid? It relates because the hinge assembly is designed to not only help lift the lid, but also to help hold it down. If your trunk lid is not going down, it is because something is stopping it from its designed operation.

I would start by removing the trunk lid and checking to see that the hinge arm does operate as designed. With the trunk lid in the open position, remove the six attachment screws while a helper holds the trunk lid. Put on a pair of leather gloves, and with care, hold tightly to one of the hinge arms. Move it downward. You will feel substantial resistance to movement. As you move it down, you will approach the center of movement. Be careful because the hinge should want to pull down hard after is goes past the point of “top dead center.” If it works as intended, it will go down below the position that would insure a fully closed trunk lid. The question is: does it pull itself down all the way below center by itself? If the hinge arms both pull down below center as they are supposed to, the lid should close all the way as well. If the hinge arms don’t go all the way down, the trouble will no doubt be with the hinge tower.


I highly recommend lubrication of all of the hinge pivot points. I put some lithium lubricant on the interlocking slides to assure that they don’t cause too much friction as well.


After checking the operation of the hinge tower assembly, and lubricating it properly, inspect it for any damage. If one or more of the hinge arms or interlocking slides is bent, cracked, rusted or deformed, you will have to repair it before you proceed.


From what you say, the trunk lid worked properly before you did your restoration. If that is true, something must have happened during the restoration to cause it to fail now. Something could have been damaged during the process, or, it may not be properly assembled now.


Once you have determined that the hinges work properly, inspect the weather strips on the lid. It is possible to install the weather strips in such a way as to cause resistance to fully closing. You may have to remove the weather strip and check the operation without it to determine that.


Another very important thing is to check to see that the lid itself fits properly. If the lid is will fitted, and closes completely without the weather strip or hinges installed, it should close properly when it is controlled by the hinges.


You may have noticed when you took the car apart that some shims may have been installed under some of the hinge attachment points to the lid. The shims that were used at the factory were usually partial faced shims. That is, the shims were installed under only a part of the hinge attachment area. If you will notice, the hinge is bolted to the lid with three screws. A partial faced shim will not fill the complete three screw area, but, instead it will be installed under only one or two of the screws at the attachment point of the hinge to the lid. By using partial face shims like these, you will be able to tilt the relationship of the hinge to the lid. This can cause the lid to fit more closely and tightly to the car. Experiment with some small round washers under the hinge attachment points and you will see how it is possible to force the lid down further at the top, or even on one side. Remember, this won’t work if the lid doesn’t fit properly, if the hinges don’t work properly or if there is something stopping the lid from coming down all the way. The factory used shims on most of the trunk lids that I have worked on over the years. The deck lids also used similar shims to help maintain a close fit.


If your hinges move freely down below center like they were designed without the lid installed, and the lid is un-obstructed and properly shaped, it should close fully. If you go through these several steps, I am confident that you will be able to find out why your trunk lid doesn’t close. Finding out why it doesn’t fit today is the key to making it fit, as it should tomorrow.