Valves

Critical inspection points and tolerances of valve are illustrated. Refer to Specifications at the end of this section for service limits. Remove all carbon from valve stems and valve heads using a fine wire brush or buffing wheel.

Inspect valve face and edge of valve head for pits, grooves or scores. Inspect stem for a bent condition and end of stem for grooves or scores. Check valve head for signs of burning or erosion, warpage and cracking. Minor pits, grooves, etc., may be removed. Discard severely damaged valves.

Visually inspect valve springs (6513), valve spring rotators and valve spring retainer keys (6518), and discard any damaged parts.

Inspect valve spring retainer keys for excessive wear and replace in pairs as required. When installing a new valve, always use new valve spring retainer keys.

Valve Stem-to-Valve Guide Clearance

Check valve stem to valve guide clearance of each valve in its respective valve guide with Valve Stem Clearance Tool TOOL-6505-F, Dial Indicator D78P-4201-G and Dial Indicator Bracketry D78P-4201-F or equivalents. Use a flat-end indicator point.

Install tool onto valve stem until fully seated, and tighten knurled setscrew firmly. Permit valve to drop away from its seat until tool contacts upper surface of valve guide.

Position dial indicator with its flat tip against center portion of tool's spherical section at approximately 90 degrees to valve stem axis. Move tool back and forth in line with indicator stem. Take a reading on dial indicator without removing tool from valve guide upper surface. Divide reading by two, the division factor for tool. If valve stem to valve guide clearance exceeds specifications listed at the end of this section, replace cylinder head (6049).

Valve Face Runout

Check valve face runout. It should not exceed specifications listed at the end of this section. If runout exceeds service limit, valve should be replaced or refaced.

Valves, Refacing

 CAUTION: Interference fit of valve and seat should not be lapped out.

The valve refacing operation should be closely coordinated with valve seat refacing operations so that finished angles of valve face of valve seat will be to specifications and provide a compression tight fit. Make sure valve grinding wheels are properly dressed.

If valve face runout is excessive or to remove pits and grooves, reface valves to specification. Remove only enough stock to correct runout or to clean up pits and grooves. If intake valve margin is less than 1.67 mm (0.066 inch) thick after grinding, replace valve or valve will run too hot in engine. If exhaust valve margin is less than 1.37 mm (0.054 inch) thick after grinding, replace valve.

Critical Valve Dimensions

 CAUTION: Do not remove more than 0.254 mm (0.010 inch) from valve stem tip.

Remove all grooves or score marks from end of valve stem, and chamfer it as necessary.

Valve Seat Runout

Check valve seat runout with suitable valve seat Runout Gauge. Follow instructions of gauge manufacturer. If runout exceeds service limit, reface valve and valve seat. Refer to Specifications at the end of this section.

Valve Seat Refacing

 CAUTION: Fit of valve and seat should never be lapped out with lapping compounds.

Refacing of valve seat should be closely coordinated with refacing of valve face so that finished seat and valve face will be concentric and specified interference fit will be maintained. This is important so that valve and seat will have a compression tight fit. Make sure valve seat grinding wheels are properly dressed.

Grind valve seats to specification listed at the end of this section. Remove only enough stock to clean up pits and grooves or to correct valve seat runout. After seat has been refaced, use seat width scale or machinist's scale to measure seat width. Narrow seat if necessary to bring it within specification. Refer to Specifications listed at the end of this section.

If valve seat width exceeds maximum limit, remove enough stock from top edge or bottom edge of seat to reduce width to specification. Refer to Specifications at the end of this section.

Use a 60-degree angle grinding wheel to remove stock from bottom of seats (raise seats) and use a 15-degree angle wheel to remove stock from top of seats (lower seats).

Finished valve seat should contact approximate center of valve face. It is good practice to determine where valve seat contacts face. To do this, coat seat with Prussian blue and set valve in place. Rotate valve with light pressure. If blue is transferred to center of valve face, contact is satisfactory. If blue is transferred to top edge of valve face, lower valve seat. If blue is transferred to bottom edge of valve face, raise valve seat.

Valve Guide Removal

The valve guides on this engine are not serviceable. Replace cylinder head if valve stem to valve guide clearance exceeds specifications listed at the end of this section.

Valve Spring Tension

Inspect the valve spring, valve spring rotators, and valve spring retainer keys for wear or damage. Discard any damaged parts.

Check the valve springs for proper pressure at the specified spring lengths using Valve/Clutch Spring Tester TOOL-6513-DD or equivalent. Apply torque until click is heard; read torque wrench and multiply reading by two. Weak valve springs cause poor engine performance. Replace any valve spring not within specification. Refer to Specifications at the end of this section. Manually rotating the valve springs while installed in the engine will not determine condition of valve springs.

Valve Spring Squareness

Check each valve spring for squareness using a steel square and a flat surface. Stand the valve spring and square on end of the flat surface. Slide the valve spring up to the square. Revolve the valve spring slowly and observe the space between the top coil of the valve spring and the square. Refer to the following illustration.

Refer to Specifications at the end of this section for out-of-square limits. Follow the same procedure for new valve springs before installation.