5_108.bk Page 35 Thursday, October 4, 2001 11:45 AM
TROUBLESHOOTING CAMSHAFT TIMING CHECK
CAMSHAFT LOBE LIFT CHECK
Correct camshaft timing is essential for proper engine performance. Incorrect camshaft timing may be suspected if soon after engine overhaul, lack of performance, unusual noise or excessive smoke is reported.
When diagnosing potential lifter or camshaft failures, 0.030 inch (0.76 mm) less than the lift of a new camshaft is considered the minimum acceptable camshaft lobe lift for used components. Intake lobe lift differs depending on the camshaft part number. Camshaft lobe lift is measured by using a dial indicator at the push rod with the rocker arm adjusted to zero lash. Refer to the chart below for the minimum acceptable camshaft lobe lift for the M-E7 camshaft.
Camshaft timing can be checked using either cylinder No. 3 or No. 4 inlet valve. For example purposes, No. 3 cylinder will be used in the following steps. 1. Remove cylinder head cover over cylinder No. 3. 2. Locate inlet valve(s) for the No. 3 cylinder (sixth valve from front of engine). Position No. 3 piston at Top Dead Center (TDC) (compression stroke).
MINIMUM ACCEPTABLE CAMSHAFT LOBE LIFT Camshaft Part No.
Exhaust Lobe
454GC5205
0.300″
Intake Lobe 0.300″
3. Loosen (back off) the inlet valve rocker adjusting screw. Ensure valve yoke is correctly adjusted. Adjust inlet valve to zero lash. 4. Position dial indicator (magnetic-base type) probe on valve spring retainer. Preload indicator to 1/2 indicator plunger travel. 5. Bar the engine in direction of normal rotation and carefully observe direction in which needle of indicator travels. Use dial indicator to determine when the inlet valve is fully open. 6. Stop rotating engine when travel of dial indicator needle stops. If dial indicator needle reverses direction, full-open position is passed. Repeat procedure. 7. Check timing indicator. Pointer should be within three degrees (retard or advance) of timing indicator specification given in following table. A difference of approximately 10 degrees indicates crankshaft-to-camshaft timing gears may be mismatched one tooth. CAMSHAFT AND TIMING INDICATOR RELATIONSHIP Camshaft Part No. 5205
Timing Indicator 27 Degrees BTDC
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