Adjusting the timing

Printed in Germany - 1988

Rough adjustment

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4. Mount the auxiliary chain tensioner, Special Tool 9401.

Illustration shows left-hand side of the auxiliary chain tensioner

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Adjusting the timing

Rough adjustment

1. Turn the crankshaft until the marking on the pulley is exactly aligned with the seam of the crankcase or with the locating mark on the blower housing.

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4. Mount the auxiliary chain tensioner, Special Tool 9401.

Illustration shows left-hand side of the auxiliary chain tensioner

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2. Position both camshafts with the punched marking pointing upwards.

Note

If this mark has not been punched, turn the camshaft until the feather-key groove points upwards.

3. Once the Z 1 marking on the pulley has been aligned with the seam and the punched marks or feather-key grooves on the camshafts are pointing upwards, the engine is in the basic ignition TDC for cylinder 1 and overlapping TDC cylinder 4.

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911 Carrera 4 Engine, Cylinder Head, Valve Drive

Illustration shows the right-hand side of the auxiliary chain tensioner

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Note

When adjusting or checking the timing, the auxiliary mechanical chain tensioner must be installed with the specified preload. The recess on the plunger may just be visible.

5. In the basic position (Item 3), one hole on the sprocket is exactly aligned with a hole on the sprocket flange. Insert the fixing pin through these exactly aligned holes.

6. Apply the hexagon head screws for the sprockets lightly. Brace with Special Tool P 9191.

Note

Apply a fine film of Optimoly HT to the thread of the hexagon head screws.

Note

If one of the camshafts has moved out of the basic position, proceed as follows: Remove the fixing pin from the camshaft which is in the basic position, to prevent it being turned during the following adjustment. Move the displaced camshaft into the basic position with Special Tool P 9191 (with the punched mark pointing upwards).

Remove the sprocket fastening screw and fixing pin and turn the crankshaft until it again reaches the Z 1 mark.

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Fine adjustment

1. Check the valve clearance and set to 0.10 mm exactly with feeler gauge B 213 b. To adjust the timing, it is sufficient if the valve clearance of the intake valves for cylinders 1 and 4 are exactly correct.

3. Now turn the crankshaft slowly from Z 1 (TDC) approx. 1 turn clockwise, observing the dial gauge. Turn until you reach the middle value of the adjusting tolerances.

Adjusting specification

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88 - 7720

4. Undo the hexagon head screw from the left-hand sprocket, remove the sprocket and pull the fixing pin out with Special Tool P 212.

5. Turn the crankshaft until the visible marking on the pulley is exactly aligned with the seam of the crankcase or the locating mark on the blower housing.

6. Remount the fixing pin and tighten the hexagon head screw lightly while bracing.

7. Turn the crankshaft two turns (720°) clockwise and check the adjustment. The value shown on the dial gauge must now be within the specified adjusting tolerance.

8. Finally tighten the hexagon head screw for the left-hand camshaft with 120 Nm (88 ftlb) with a second mechanic bracing with Special Tool P 9191.

Adjusting the camshaft, right (cylinder 4)

1. Adjust cylinder 4 to ignition TDC (overlapping cylinder 1).

2. Repeat the adjustment procedure as described under fine adjustment Items 2 to 8 for cylinder 4.

Adjusting the camshaft, left (cylinder 1)

2. Fasten the dial gauge to the stud bolt on the camshaft housing with holder P 207. Set the dial gauge to 0 on the spring seat from intake valve with the valve closed and with approx. 10 mm preload.

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911 Carrera 4 Engine, Cylinder Head, Valve Drive

3. Once the adjustment has been completed, remove the auxiliary chain tensioner and install the original chain tensioner. Observe the installation position.

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A - Left-hand chain tensioner. Oil feed hole points upwards.

B - Right-hand chain tensioner. Oil feed hole points downwards.

Note

The chain tensioner spring seats are also marked with 'lop" and "bottom left" or "bottom right".

Engine timing

Printed in Germany - 1988

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