Common Manual: Lift Kit
The optional lift kit typically lifts one end of the car (the front, normally), but additional rams can be obtained to lift the entire car if necessary. Most SL-C owners find that the front end lift is adequate, as there is very little rear overhang, and normally sufficient ground clearance.
Due to the space that the hydraulic rams take up on the shock absorbers you will need to fit shorter springs to accommodate them. The optimal spring length is 4” when using the lift kit, though some builders have reportedly found 6” springs to work in some cases.
If you have ordered the lift kit at the same time you ordered the car, the car will ship with the shorter springs required. Standalone lift kit orders don't come with springs, and you'll have to supply your own. For reference, the stock springs are normally 600 lbs/in for the front, so you can start there when ordering new ones. Alternate springs in a wide range of lengths and spring rates can be obtained from the usual sources like Hyperco, Eibach, Swift, and QA1.
Begin with the same spring rate as your kit has originally. Most springs have a tag of some sort, are marked on the spring with paint, or have the spring rating engraved on the spring tang.
On the front, the rams can be fitted on top of the springs or below the springs. On the rear, the rams can only be run on the bottom of the shock. Below are photos of an example installation.
The preferred mounting position is to have the rams mounted on top of the spring, opposite to the picture above. This places the rams in an unsprung position, puts the grub screws where they are most useful for bleeding and improves access to the fittings. Either way will work, but mounting at the top of the spring is the optimal solution.
The next picture shows how the rams can be used to lift not only the front of the car, but also the rear, in cases where that is desirable. For most situations, just the fronts need rams as the rear of the car has very good approach and departure angles, unlike the front. However, rear-mounted rams can improve ground clearance at the back of the car in cases where that is needed.
Note the location of the pump in the following picture. This is a typical installation, though the pump is mounted on its side. This is acceptable, but the pump manufacturer recommends a “motor up” configuration.
Plan your installation to keep the lines as short as reasonably possible.
The next photo shows one possible mounting hole placement for the reservoir (top) and the mounting holes for the hydraulic pump.
The pump unit has 3 ports in it. The “R” port is for connection to the fluid reservoir. Plug one of the remaining ports (either A or B) and using a “T” connector, pressurize the rams from the other port as shown in the picture below.
The switch supplied with the kit is pre-configured for the lift kit, and there is wiring for this switch in the standard Infinitybox harness. It reverses the polarity to the pump to make the pump either push fluid or retract fluid. You can use the DPDT switch provided with the kit, or substitute your own. Actually wiring the lift kit is trivial- there are two wires in the front Infinitybox harness marked for the lift pump; connect them (in either orientation- it doesn't matter) to the pump wires and that's it for the pump. The Inifinitybox harness in the cockpit already has the DPDT switch and wiring done for you, so you just have to mount the switch where you prefer it.
The lift kit rams have air bleed outlets in them, in the form of grub screws. To successfully bleed the air out, these will need to be positioned at the top of the ram. It may be necessary on the front to bleed the rams before final installation or to orient the ram so that the bleed outlets are at the highest point. If you do decide to mount the rams at the bottom of the shock, you can sometimes bench bleed the rams by opening the grub screws and pumping fluid through them until no air bubbles are present in the stream. Close the grub screws and bleed the rams on the car as necessary.
Use only a high quality 10 to 40 CST hydraulic mineral oil, and replace it every two years or so to purge it of any contaminants. If you aren’t sure where to source good quality hydraulic fluid, the manufacturer recommends a good quality power steering fluid. Never run the pump without oil as it will destroy itself in short order.
The picture above shows how to connect the system. This picture shows a newer pump design; not all pumps look the same, but all work in essentially the same manner. Your pump may not have a visible relief valve as shown here.
Note the plugged port on one side, and the use of a “T” fitting to pressurize and drain the two rams (the yellow line represents an actual braided line connection to the rams from the pump). The red hose in the picture goes to the plastic fluid reservoir.