Servicing, Aligning and Mounting Conrod Bearings

NOTE: For additional information on the C36 model not specifically listed below refer to AMG.





C36 information:
Connecting rod length (L) has been changed to 144 mm to accommodate a different stroke.
Small end has been machined to ensure piston clearance

Repairing
1. Remove conrods.
2. Check conrod bolts.
3. Oil thread and bolt head contact surface and install bearing cap. Tighten to 40 Nm.





4. Measure conrod bearing basic bore (Fig. A).

NOTE: If basic bore exceeds the value of 51.619 mm or is conical, dress contact surface of conrod bearing cap to max. 0.02 mm. Machine conrod cap together with conrod.

5. Press in new conrod bush (Fig. B).

NOTE:
^ Press in new conrod bush so that the oil drillings are aligned (arrows).
^ Insertion pressure 2450 N.

6. Turn or ream conrod bush.
7. Dress on a dressing plate contact surfaces of conrod at side.

Aligning
1. Check conrod with bearing shells and piston pins installed with conrod inspection equipment.
2. Align conrod with conrod aligning equipment.





3. Align parallelism of conrod bearing bore to contort bush bore (Fig. C).
4. Align twist of conrod boating bore to conrod bush bore (Fig. D).





Specifications
Length, Bearing Bore To Conrod Bush Bore (L) (see footnote [1]):
C280: 148.995 - 149.005 mm
C36: 144.000 mm
Conrod:
Bearing Shell Basic Bore (D1): 51.600 - 51.619 mm
Bush Basic Bore (d1): 24.500 - 24.571 mm
Bush Inner Diameter: 22.007 - 33.013 mm
Permissible Difference:
In Axial Parallelism (see footnote [2]): 0.07 mm
In Concentricity Of Conrod Bearing Bore: 0.01 mm
In Weight Of Complete Conrod With An Engine: 4 grams
Peak-To-Valley Height Of Conrod Bush On Inside: 0.005 mm
Twist Of Conrod Bearing Bore To Bush Bore: 0.15 mm
Piston Pin Play In Conrod Bush: 0.013 - 0.018 mm
Width Of Conrod:
At Bearing Bear (B): 21.948 - 22.000 mm
At Bush Bore (b): 21.948 - 22.000 mm
Conrod bearing play:
Axial: Piston Guided
Radial: 0.02 - 0.04 mm

[1]: Center of conrod bearing bore to center of conrod bush bore.
[2]: Permissible difference in axial parallelism of conrod bearing bore to conrod bush bore.


Fitting New Bearings

NOTE:
^ Conrods which have been overheated because of bearing damage (blue discoloration) must not be re-used.





^ Conrod and conrod caps are marked together (arrow).
^ The conrod shaft must not have any cross scores and notches.
^ Conrods with machined conrod bush are supplied as a replacement part.
^ The conrod and the conrod cap are located relative to each other with fit sleeves.
^ Pay attention to difference in weight when replacing the conrod.





1. Measure and note conrod basic bore.
2. Measure and note bearing journal diameter.
3. Calculate conrod radial bearing play.
4. Match conrod bearing shell
5. Install conrods on pistons