Valve Train Analysis

Engine

Valve Train Analysis

The following component tests are used to diagnose valve train concerns.

Valve Train Analysis - Engine Off - Valve Cover Removed

Check for damaged or severely worn parts and correct assembly. Make sure correct parts are used with the static engine analysis as follows.

Valve Train Analysis - Engine Off, Camshaft Roller Followers and Hydraulic Lash Adjusters, Overhead Camshaft

- Check for loose mounting bolts on camshaft carriers.

- Check for plugged oil feed in the camshaft roller followers, lash adjusters or cylinder heads.

Valve Train Analysis - Engine Off, Camshaft - Engines

- Check for broken or damaged parts.

Valve Train Analysis - Valve Springs

- Check for broken or damaged parts.

Valve Train Analysis - Engine Off, Valve Spring Retainer and Valve Spring Retainer Keys

- Check for correct seating of the valve spring retainer key on the valve stem and in valve spring retainer.

- Check for correct seating on the valve stem.

Valve Train Analysis - Engine Off, Valves and Cylinder Head

- Check for plugged oil drain back holes.

- Check for worn or damaged valve tips.

- Check for missing or damaged guide-mounted valve stem seal.

- Check for damaged hydraulic lash adjuster.

- Check installed valve spring height.

- Check for missing or worn valve spring seats.

- Check for plugged oil metering orifice in cylinder head oil reservoir (if equipped).

Static checks (engine off) are to be made on the engine prior to the dynamic procedure.

Valve Train Analysis - Engine Running, Valves and Cylinder Head

- Check for plugged oil drain back holes.

- Check for missing or damaged valve stem seals or guide mounted valve stem seals.

- Check for a plugged oil metering orifice in the cylinder head oil reservoir.

If insufficient oiling is suspected, check oil passages for blockage, then accelerate the engine to 1,200 rpm with the transmission in NEUTRAL and the engine at normal operating temperature. Oil should spurt from the rocker arm oil holes such that valve tips and camshaft roller followers are well oiled. With the valve covers off, some oil splash may overshoot camshaft roller followers.

Valve Train Analysis - Camshaft Lobe Lift

Check the lift of each camshaft lobe in consecutive order and make a note of the readings.

1. Remove the spark plugs.

2. Install the Dial Indicator Gauge with Holding Fixture so the rounded tip of indicator is on top of the camshaft lobe and on the same plane as the hydraulic lash adjuster.

3. Rotate the crankshaft using a breaker bar and socket attached to the crankshaft pulley retainer bolt. Rotate the crankshaft until the base circle of the camshaft lobe is reached.





4. Zero the Dial Indicator Gauge. Continue to rotate the crankshaft until the high-lift point of the camshaft lobe is in the fully-raised position (highest indicator reading).

5. To check the accuracy of the original indicator reading, continue to rotate crankshaft until the base circle is reached. The indicator reading should be zero. If zero reading is not obtained, repeat Steps 1 through 5.

6. If the lift on any lobe is below specified service limits, install a new camshaft and camshaft roller followers.

7. Install the spark plugs.