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Valve Timing

  1. Rotate crankshaft until mark "Z1" on crankshaft pulley aligns with joint of crankcase or stripe on fan housing. Position both camshafts so that punch marks face up. See Fig 1.
  2. Engine has its basic setting (cylinder No. 1 = TDC and cylinder No. 4 = overlap) by adjusting mark Z1 on pulley to joint and punch marks on camshafts to face up. In the position described, one bore in sprocket will be exactly aligned with a bore in sprocket flange.
  3. Insert a locating pin in these exactly aligned bores. Tighten hexagonal bolts for sprockets with special holding wrench (P 9191). If one of the camshafts is turned out of the basic setting position, remove the locating pin from camshaft in basic setting position.
  4. Turn mislocated camshaft to basic setting position (punch marks face up) with holding wrench 9191. Remove sprocket mounting bolt and locating pin, and turn crankshaft to mark "Z1" again. Check valve clearance and, if necessary, adjust to exactly 0.04" (0.1 mm) with feeler gauge (213).
  5. Exact clearance of intake valves on cylinders No. 1 and 4 is sufficient for timing adjustments. Preload the timing chains using special lever (9182). Do NOT use a screwdriver to preload chains. Mount the dial gauge on the stud of the camshaft housing with dial gauge holder (207).
  6. Set dial gauge to zero on spring retainer of intake valve for cylinder No. 1 with valve closed and approximately 0.40" (10 mm) preload. Slowly turn the crankshaft clockwise from "Z1" about 1 turn and observe dial gauge at the same time.
  7. Continue turning until the mean value of the adjusting tolerance (valve lift) is reached. A range of 0.055 - 0.067" (1.4 - 1.7 mm) is acceptable, with 0.061 (1.55 mm) ideal.
    Fig 1: View of Engine from Blower End (Rear of Vehicle) Showing Valve Timing Marks
    G09332240Courtesy of PORSCHE CARS NORTH AMERICA, INC.

    "Z1" on crankshaft pulley should align with joint of crankcase or stripe on fan housing. 

    Unscrew and remove mounting bolt on left sprocket and pull out the locating pin with puller (P 212).

  8. Turn crankshaft accordingly until mark "Z1" on the pulley is aligned with joint of crankcase or stripe on fan housing. Install locating pin and tighten bolt finger tight, while holding pulley. Turn crankshaft clockwise 2 turns and recheck setting. Indicated value should be within tolerances.
  9. Tighten bolt of left camshaft to final torque of 86 ft. lbs. (120 N.m), having a second person hold sprocket with holder (9191). Set cylinder No. 4 to TDC (cylinder No. 1 overlaps). Repeat adjusting procedures described above on cylinder No 4.
INTAKE VALVE LIFT

Application In. (mm)
911SC .055-.067 (1.4-1.7)
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