User manual PORSCHE 968 ASSEMBLY INSPECTION PROCEDURE AND MAINTENANCE SCHEDULE

[. . . ] These periodic inspections will provide regular checks of the health of your Variocam and its related parts and should ensure that wear or other problems are detected before they result in catastrophic failure. Overview of Variocam Operation Due to the apparent lack of detailed information on Variocam operation from Porsche, the following section is based on the authors' understanding, derived from various articles and personal observations. Variocam is a mechanism that allows the intake camshaft timing to be varied for different engine operating conditions, thereby maximizing torque. In the 968 engine, the exhaust camshaft is driven by a toothed rubber belt from the crankshaft. Halfway along the length of each camshaft is a toothed sprocket and a connecting chain that transfers drive to the intake camshaft from the engine driven exhaust camshaft. [. . . ] In the absence of any documented recommendations from Porsche, we believe that by following these steps, you should have better protection against catastrophic failures. However, we cannot guarantee this, and recommend that you seek expert advice if you have any doubts about the condition of your Variocam components. These include: · · · Before starting work, disconnect the battery Wait until the engine has fully cooled before starting work Work in a well ventilated area and avoid naked flames or other combustion sources Also, when working on the engine, it's very easy to dent the front wings (fenders) by leaning on them. Place soft covers (old blankets are ideal) over them to prevent scratches and don't lean on them. Tools Required: · · · · · · · · 17mm and 19mm good quality open ended spanners (wrenches) Strong light source Old rags Inspection mirror (small dentists-type is ideal) Hexagon drive bits, sizes 4mm and 5mm, and suitable driver Spark plug socket, drive extension, and handle 24mm deep 6 point socket and ratchet drive handle Torque wrench with range to cover 10 Nm / 7 ft. /lbs (desirable) Parts Required: (assuming no repairs needed as a result of inspection) The following parts may be required if the existing items are damaged but it is usually possible to re-use the old parts: · · Cam cover gasket (quantity 1) o Part number 928 104 447 09 Sealing rings/grommets (quantity 4) for sealing the spark plug recesses o Part number 928 104 443 08 Inspection Procedure: 1. Remove four hexagon socket head screws securing aluminium trim panel over cam cover/fuel rail, remove "Variocam" badge and trim panel. Remove two hexagon socket head screws securing seal retainer around Variocam solenoid body and gently pull off seal retainer and gasket. Place rags beneath connections on two fuel hoses at rear of cam cover (see figure 1). Take care to ensure that the fittings nearest brake master cylinder are held stationary and not twisted. Note: a few ml's of fuel will be spilled during the process, hence the rags. Gently pull fuel lines clear of the cam cover, taking care not to kink the lines. Insert clean rags into spark plug recesses to avoid risk of dropping loose objects into cylinders. Note that these screws do not need to be removed from the cover once released but be aware that they are not held captive in the cam cover and may drop out when the cover is removed. It may be necessary to apply leverage but be careful and do not insert any sharp objects between the sealing faces. The black rubber seal can either stay in place on the engine, or stay attached to the cam cover. When withdrawing the cover, it's often needed to peel the seal away from parts of the engine or cover. IF COVER SCREWS ARE STILL IN THE COVER, TAKE CARE THAT THEY DON'T FALL OUT AND DROP INTO THE EXPOSED ENGINE!Note that there are four black circular rubber seals around the spark plug recesses. These will hopefully stay attached to the engine when the cover is removed but may pull away with the cover. Take great care not to drop anything into the engine, as there are oil drain galleries below the exhaust camshaft and screws, dirt, or small tools can easily find their way into the engine. Using the light source and mirror, carefully and methodically inspect the upper and lower tensioner pads, both camshaft sprockets, the metal oil pipe feeding oil to the tensioner body, and the shiny piston rod of the upper tensioner for wear or scoring (see figures 2 & 3). These checks are very subjective, there is no test gauge or tool to measure anything. [. . . ] This is a costly option, but gives you at least 60, 000 miles, and following the maintenance many more , of trouble free Variocam functioning; 2) Search for two used camshafts in good condition, coming from same engine (or matched by a true expert from different cars). Suggested maintenance schedule The following schedule applies in case of normal (road) use of the car. If your car is in an "unknown" status , that is in case of missing/unreliable information about previous Variocam inspection/maintenance, as soon as possible carry out the inspection procedure detailed above. Miles Unknown or greater than 60, 000 Km Unknown or greater than 100, 000 Action Immediately inspect the Variocam, following the procedure above. See also the section above regarding "wear limits" It is highly recommended to do the Variocam inspection before buying a new car, as part of the pre-purchase inspection: this avoids big $$ bills for hidden problems, can be used to lower the car value, can avoid catastrophic failures when driving the car to home garage. [. . . ]