If the camshaft and crankshaft
drive gears require replacement, this can be done
with the engine in the car. Manufacturers of engines
with pressed-fit camshaft gears make special tools
that can be used to hold the cam forward during gear
installation.
NOTE
If the cam sprocket is the nylon type and
chunks of gear teeth are missing, the oil
pan must be removed in order to extract
teeth from the oil pump screen and oil pan.
This oil pump sprocket is
filled with the teeth of a nylon timing sprocket
that failed.
Replacing A
Camshaft Gear
When replacing a
pressed-fit camshaft gear, use a puller to
remove it from the cam.
Disconnect the
negative battery cable.
Remove the covers
protecting the camshaft drive gears.
Check for proper
alignment of the timing marks on the
timing gears.
Remove the timing
gears according to the service manual.
Clean the timing
gears.
Inspect the gears
for wear or cracks, and replace
necessary parts.
After replacing any
worn or damaged gears and drives, set
the timing marks according to the
service manual.
Rotate the engine
through two complete rotations of the
crankshaft. Check to see if the timing
marks on the gears are still in proper
alignment.
Reinstall all
covers removed for access.
Reconnect the
negative battery cable and start the
engine.
Set the ignition
timing to the manufacturer's
specifications.
Installing A
Camshaft Gear
When reinstalling the
gear, take care that the cam does not move
to the rear; it could knock loose the core
plug in the rear of the block or chip cam
lobes on neighboring lifters.
The rear of the cam
gear must be supported while the cam is
pressed from its center.
After the new cam
gear is pressed on, end play is checked
with a feeler gauge.
Checking the
clearance behind the thrust plate to
determine camshaft end play. Courtesy of
Federal Motors Corporation, Service
Technology Group.
The clearance
between a cam thrust plate and the
sprocket or gear varies from
0.0015" to 0.005".
If a spacer is
used, it must be from 0.0015" to
0.005" thicker than the thrust
plate.
The cam will press
against the spacer, which fits inside
the thrust plate hole, controlling end
thrust.
In some cases,
adjustment is made by replacing the
thrust plate.
Some engines limit
the end play of the camshaft through the
use of a cam button.
A nylon button or
torrington bearing sets on a spring and
is installed between the camshaft timing
gear and the timing chain cover.
Aluminum gears can
be heated for easier installation.
NOTE
Do not forget the spacer on a cam
with a bolt-on sprocket. The result
could be a cam that will not turn
after the bolt is tightened.
