Oldsmobile Engine >> RESTORING WORN CAM GEAR THRUST SURFACES

Oldsmobile Engine >> RESTORING WORN CAM GEAR THRUST SURFACES

Method To Restore Worn Cam Gear Thrust Area On
Some Engine Blocks

Many late model engines (Chevrolet small block and 6.5L (396
CID), Dodge & Plymouth 3.4L (225 CID), Oldsmobile 4.0 & 4.3L (425
& 455 CID), Buick 4.1L (401 CID) and others) do not have camshaft
thrust washers, but depend upon the mesh of the distributor drive
gear to retain the camshaft. Often the cam gear or sprocket
causes the front of the block to wear to such an extent that
repair is needed to return the block to service.

A relatively easy yet effective repair is suggested:

(1) Make a metal brush (similar to a cam bearing drive plug)
approximately 2 long with the outside diameter to fit the
cam bearing housing bore. Provide a slight taper on the
O.D. to prevent the bushing from going all the way through.
Drill an inner hole in the bushing to accept a valve seat
installation pilot. Modify a valve seat cutter shank to be
turned by 1/2 electric drill and attach a cutter head
proper diameter to match the O.D. of the worn circle.

(2) Cut the front of the block the depth of a Y91
Continental main bearing thrust washer. The O.D. of the
thrust washer should be machined to press fit in the
machined counterbore. The I.D. of the thrust washer should
be machined to fit freely over the cam bushing. The Y91
thrust washer should then be installed.

After tooling up for this operation, the entire procedure should
take no more then five minutes and the only cost is that of the
thrust washer.

NOTE: Depending upon your valve seat equipment, it may be
necessary to change the above tooling to accommodate your
equipment.

The AERA Technical Committee


April 1973 - SPB 18

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