Clamshell Adjustment

Maurice writes:

Well, Spring has finally arrived, and it has inspired me to finish a DIY that I had been working on for those who have "clamshell problems"

The two areas to start to evaluate what may not be properly aligned are:

1. How the left to right forward edge of the clamshell sits and fits against the base of the canvas on top of the rear main bow, and;

2. Whether the clamshell has been previously “tweaked” by a malfunctioning top mechanism.

If you think the clamshell is being restricted from going down by the rear main bow of the convertible top frame, you can adjust that by putting more pressure on the tension rope. That will pull the rear main bow down slightly, and this can be adjusted at each side to get the bottom rear of the canvas top even and level. The lower steel ball cup of the tension rope is pressed onto a steel ball that adjusts up and down by means of an adjusting bolt. In the next two photos you can see the top of the 14mm adjusting bolt and the detail of how the adjusting bolt appears underneath the foam drain tray. It sits to the inboard side of the lower end of each of the two tension ropes.

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Turning it counterclockwise will increase the tension and pull the rear main bow down. Keep in mind that this will have some effect on how much the rear main bow will pull back on the leading edge of the top where it mates up to the windshield frame.

You also have to determine whether the clamshell itself is not tweaked and actually would lay flat if it wasn't attached to anything. If it's tweaked, you can straighten it out by putting some pressure on one side, at the same time that another person is pressing down on the opposite side. If that doesn’t get it completely flat, you may get a better result by disconnecting the clamshell from the V-Levers and then by popping out (pull inboard) the steel ball at the lower end of each body-colored clamshell support arm from its black plastic slider. (See the parts to which the red and the yellow arrow point. The steel ball is outboard of the nut to which the yellow arrow points, and “hidden” inside the black plastic slider).

Be careful when you pop off the black “hydraulic” pushrod from the V-Lever as in certain positions it is under a great deal of pressure. If your clamshell has gotten severely tweaked because only one V-lever was being driven, you may have to remove the clamshell entirely and straighten it on a bench. Also, remember to go easy on these steps when you are pressing down on the clamshell, as you don’t want to “overstraighten” it.

If the clamshell is straight but still does not sit flush with all of the surrounding body panels, then there are three adjustment points that you can use to regulate the height at which the various parts of the clamshell sit:

1. For the rear horizontal surface, the large plastic nut under each corner of the rear of the clamshell (32mm?).

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You will find one rubber bumper on the underside of each rear corner of the clamshell that “bumps into” and centers itself into the middle of these large plastic nuts.

2. For the front "tongues", the small rectangular plastic tab that sits on the body under the very front part of the clamshell. Pushing the two parts together will raise the front of the clamshell on that side, pulling them apart will lower that side.

3. The nut and slotted screw onto which the body-colored support arm of the clamshell is attached at its bottom. You can loosen the nut while holding the slot in the center of the screw with a small flat-blade screwdriver. When the nut is loose, you can turn the screw while observing its eccentric action on the opposite side of the clamshell support arm. Be sure to lock the nut when you are satisfied with that adjustment. In the following photo, the red arrow is pointing to the slotted screw inside the nut, and the yellow arrow is pointing to the black plastic slider into which the steel ball is pressed.

You can also take advantage of this occasion to lubricate the channel in which the slider goes back and forth.

One word of caution: Before you make any of these adjustments, make sure that you mark all of the starting positions because all of these adjustments have an effect on other seemingly unrelated parts of the clamshell and top assembly.

Nothing like springtime for making your Boxster a little better looking!