| Mercury Engine >> BROKEN ROCKER ARM BOLTS |
Broken Rocker Arms On
Ford (Mercury) 5.8L (351 CID) Engines
Broken valve rocker arm bolts due to fulcrum to pedestal boss interference have been experienced in some Ford 5.8L (351 CID) Engines.
When encountering these trouble cases, check all remaining rocker arm bolts for breakaway torque turning the bolt clockwise, and checking all push rods for straightness. Bolts with breakaway torque under 20 ft.lbs. should be replaced using Part No. DOOZ- 6A527-A-5/16_18 x 1.38 bolt Grade 8 material.
All fulcrums in these problem engines must be reworked as follows: Grind and/or file the piloting chamfer edges as shown in the illustration, and remove all flared edges both on the side and bottom surfaces. If necessary buff or polish the sides of the fulcrum to ensure that it is free in the fulcrum channel.
To eliminate possible inaccurate torque readings caused by thread imperfections, lubricate the bolt threads and underside of the bolt head with engine oil. Assemble the rocker arm, fulcrum seat, bolt to the engine, and torque the bolts 20-25 ft.lbs. Then back the bolt out 4 full turns and retorque 20-25 ft.lbs. The rocker arm bolt torque has been revised from 17-23 ft.lbs. to 20-25ft.lbs.
To cut down on additional wear, mark the fulcrums so they can be installed in their original position and location in the rocker arms. Do not rotate the fulcrums 180°.
The AERA Technical Committee
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