Chevrolet 10 Series 1968, Service Manual

Page: 368 / 713

ENGINE 6-21
TIMING
MARKS
THRUST
PLATE
SCREWS
Fig. 15L—Timing Gear Marks
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 indica­
tor with specifications.
6. Continue to rotate the crankshaft until the indicator
reads zero. This will be a check on the accuracy of
the original indicator reading.
7. If camshaft readings for all lobes are within speci­
fications, remove dial indicator assembly.
8. Install and adjust valve mechanism as outlined.
Rem oval
1. Remove valve lifters as outlined.
2. Remove crankcase front cover as outlined.
3. Remove grille as outlined in Section 13.
4. Remove fuel pump as outlined in Section 6M.
5. Align timing gear marks then remove the two cam­
shaft thrust plates screws by working through holes
in the camshaft gear (fig. 15L).
6. Remove the camshaft and gear assembly by pulling
it out through the front of the block.
NOTE:
Support camshaft carefully when re ­
moving so as not to damage camshaft bearings.
Installation
1. Install the camshaft and gear assembly in the engine
block, being careful not to damage camshaft bearings
or camshaft.
2. Turn crankshaft and camshaft so that the valve tim­
ing marks on the gear teeth will line up (fig. 19L).
Push camshaft into position. Install camshaft thrust
plate to block screws and torque to specifications.
3. Check camshaft and crankshaft gear run out with a
dial indicator (fig. 16L). The camshaft gear run out
should not exceed .004" and the crankshaft gear run
out should not exceed .003".
4. If gear run out is excessive, the gear will have to be
removed and any burrs cleaned from the shaft or
the gear will have to be replaced.
5. Check the backlashlash between the timing gear teeth
with a dial indicator (fig. 17L). The backlash should
not be less than .004" nor more than .006".
6. Install fuel pump as outlined in Section 6M.
7. Install grille as outlined in Section 13.
8. Install crankcase front cover as outlined.
9. Install valve lifters as outlined.
Tim ing G ears
Replacement
With camshaft removed, crankshaft gear may be re­
moved using Tool J-8105 (fig. 18L). To install crankshaft
F ig . 16L—C h eckin g Camshaft G e a r Runout
F ig . 17L—Ch eckin g Timing G e a r Backlash
CHEVROLET TRUCK SERVICE MANUAL