Bushed Rocker Arms
The stock rocker arms were never bushed, and the tolerances specified are based to the cast iron on steel interface. This translates to a clearance of 0.0028" to 0.0033". If your rockers are worn, both the rockers and the rocker shaft must be replaced. If the bore diameter in the new rocker is on the high side, and your rocker shaft is on the small side of the tolerance, the clearance will be close to the maximum allowed. In addition, the stock components will wear more quickly than rocker arms fitted with bushings.

We have contracted for bushed rocker arms to be made for us by a specialty supplier in England. The rockers are identical to the OE rocker in shape, but they are sized for and fitted with a bronze bushing. They must be matched to a specific rocker shaft by honing the bushings. We suggest a rocker arm bushing-to-shaft clearance of 0.002" to 0.003".

The advantages are numerous. With bushings honed to fit, the rocker arms and the rocker shaft will last longer. With the tighter tolerances, you will not lose as much oil pressure as you would with the stock un-bushed rocker arms. The other critical area for wear is the tip, which comes in contact with the valve stem. The tips are very hard, 50-52HRC (Rockwell C scale), which is the same as new unused rocker arms. Moss also offers matched sets of rocker arms and rocker shafts, with the bushings already honed to give a clearance of 0.002" to 0.003."

839-115 & 839-125 Spec Sheet
839-128 Instruction and Information Sheet
839-138 Instruction and Information Sheet

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