TM 5-3895-346-14
CAMSHAFT AND BEARINGS
ENGINE OVERHAUL
CAMSHAFT, BALANCE SHAFT, AND BEARINGS
The camshaft and balance shaft used in the in-line engines are located just below the top of the cylinder block.
The camshaft and balance shaft in the in-line engines may be positioned on either side of the engine as
required by the engine rotation and accessory arrangement.
The accurately ground cams ensure efficient, quiet cam follower roller ac- tion. They are also heat treated to
provide a hard wear surface.
Both ends of the shafts are supported by bearings (bushing-type) that are pressed into bores in the cylinder
block. The balance shaft is supported by front and rear bearings only, whereas the camshaft is supported by
end, intermediate, and center bearings. Two end bearings (front and rear), two intermediate bearings, and a
center bearing are used in the four-cylinder engines to support the camshafts.
To facilitate assembly, letters signifying the engine models in which a shaft may be used are metal stamped on
the ends of the shaft. The letters on the timing gear end of the camshaft must correspond with the engine
model. For example, the letters RC are stamped on a camshaft used in an RC-model engine. For additional
identification, a camshaft with no designation on the ends or a 7 stamped on the ends is a high-velocity, high-
lift camshaft. A camshaft metal stamped with a V or V7 is a low-velocity, high-lift camshaft. Effective with
engine 4D-112278, new camshafts metal stamped V7L are used intermittently in the four in-line engines.
These are low-velocity, low-lift camshafts.
On 4-53 engines, the present low-lift camshaft must be used in conjunction with the new exhaust valve springs.
Refer to Exhaust Valves.
IMPORTANT
Failure to change the exhaust valve springs could result in broken springs and
engine failure.
NOTE
The low-lift camshaft which provides a maximum valve cam lobe lift of 0.276 inch
is stamped V7L on both ends.
To provide proper camshaft end thrust, a new front camshaft pulley spacer is being used and the oil slinger has
been eliminated, effective with engine serial number 4D-164682. Engines built prior to 1968 were built with an
oil slot broached in the camshaft end bearing. With pressure oil from this slot flowing directly on the upper front
cover oil seal, the seal required the protection of an oil slinger. Even though the slot was eliminated in 1968,
the use of the slinger was continued. With the elimination of the oil slinger, a new 0.025-inch longer spacer is
used to make up for the removal of the slinger. Therefore, when removing the oil slinger(s) from an engine
built prior to the above serial number, it will be necessary to replace the shorter spacer(s) with the new 0.025-
inch longer spacer. Removal of the oil slinger on former engines is not mandatory.
NOTE
The former short spacer and slinger are for engines built prior to 1968 (engine
serial number 4D-48900).
The new spacer is identified with a black oxide finish, the same part number also incorporates an optional
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