Usage:
3500 Family Of Engines
Description of Change: A new crankshaft counterweight bolt and washer are used in the 3500 Family of Engines. The bolt has a larger radius under the head. The radius is rolled to provide compressive stresses in the fillet. Also, the bolt head has a thicker flange. These changes will prevent breakage of the bolt at the radius.
The new counterweight bolts are assembled with hardened washers which have a chamfer on the inside diameter for clearance with the bolt head radius. The washers are added to prevent galling under the bolt head when the bolt is tightened. This will provide a more consistent torque on the bolt.
Adaptable To: The new 7E4201 Bolt and 7E4725 Washer, when used together, are direct replacements for the former 4W6358 Bolt which has been canceled.
The new 7E4201 Bolt is adaptable to earlier 3500 Engines. However a measurement of hole "A" will determine which washer is needed with the bolt. See Illustration 1 for hole dimension and location. If the hole measurement is 32.5 mm (1.28"), use a 7E4202 Washer. If the hole measures 27.0 mm (1.06"), use a 7E4725 Washer.
Illustration 1. Location of counterweight bolt holes.
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Do not use the 9Y3830 Washer, which was used on crankshafts in 3508 Engines, with the new 7E4201 Bolt. The inside diameter of the 9Y3830 Washer will contact the bolt head radius which can cause a notch and result in a broken bolt. See Illustration 2.
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Illustration 2. New 7E4201 Bolt with former washer and new washer.
NOTE: Replace all old counterweight bolts if one fails. This will reduce the chance of future bolt head failures.
The new bolt can be identified by markings on the top of the bolt head. The new bolt is marked with /bq/CAT/eq/ while the former bolt is marked with /bq/CWT./eq/ With the thicker bolt head flange, there is less gripping surface for a socket on the 12 point head. Use special care when tightening the new bolts to avoid damaging the socket.