Chevrolet 10 Series 1968, Service Manual

Page: 383 / 713

ENGINE 6-36
the inside of cover and drive it into position with
Tool J-8340 on 307 and 327 cu. in. engines (fig. 15V)
or Tool J-22102 on 366, 396 and 427 cu. in. engines
(fig. 16V).
Timing Chain and/or Sprockets (307 and 327)
Replacement
1. Remove torsional damper and crankcase front cover
as outlined.
2. Crank engine until marks on camshaft and crankshaft
sprockets are in alignment (fig. 17V).
3. Remove camshaft sprocket to camshaft bolts.
4. Remove camshaft sprocket and timing chain together.
Sprocket is a light press fit on camshaft. If sprocket
does not come off easily, a light blow on the lower
edge of the sprocket (with a plastic mallet) should
dislodge the sprocket.
5. If crankshaft sprocket is to be replaced, remove
sprocket using Tool J-5825 (fig. 18V). Install new
sprocket using Tool J-5590 (fig. 19V).
6. Install timing chain on camshaft sprocket. Hold the
sprocket vertical with the chain hanging down and
orient to align marks on camshaft and crankshaft
sprockets (fig. 20V).
NOTE: Do not attempt to drive sprocket on
camshaft as welsh plug at rear of engine can
be dislodged.
7. Draw camshaft sprocket onto camshaft, using the
three mounting bolts. Torque to specifications.
8. Lubricate timing chain with engine oil.
9. Install crankcase front cover and torsional damper
as outlined.
Camshaft
M easuring Lobe Lift
NOTE: Procedure is similar to that used for
checking valve timing. If improper valve opera­
tion is indicated, measure the lift of each
push rod in consecutive order and record the
readings.
1. Remove the valve mechanism as outlined.
2. Position indicator with ball socket adapter (Tool
J-8520) on push rod (fig. ).
NOTE: Make sure push rod is in the lifter
socket.
3. Rotate the crankshaft damper slowly in the direction
of rotation until the lifter is on the heel of the cam
lobe. At this point, the push rod will be in its lowest
position.
4. Set dial indicator on zero, then rotate the balancer
slowly, or attach an auxiliary starter switch and
“ bump” the engine over, until the push rod is in
fully raised position.
C A U TIO N : The primary distributor lead must
be disconnected from the negative post on the
coil and the ignition switch must be in the on
position. Failure to do this will result in a
damaged grounding circuit in the ignition switch.
5. Compare the total lift recorded from the dial indi­
cator with specifications.
n
F ig . 2 0 V —In stalling Timing Chain F ig . 21V —Measuring Camshaft Lobe Lift
CHEVROLET TRUCK SERVICE MANUAL