Valve Spring: Service and Repair
REMOVALCYLINDER HEAD OFF
1. With cylinder head removed, compress valve springs using the valve spring compressors shown in (Fig. 44).
2. Remove valve retaining locks, valve spring retainers and valve springs.
3. Remove valve stem seal assembly.
CYLINDER HEAD ON
1. Remove the cylinder head cover.
2. Remove rocker arm shafts assemblies.
3. Rotate crankshaft until piston is at TDC on compression stroke.
4. With air hose attached to adapter tool installed in spark plug hole, apply 90 - 120 psi air pressure.
5. Using Special Tool MD-998772A with adapter 6779 (Fig. 45) compress valve springs and remove valve locks.
6. Remove the valve spring.
7. Remove the valve stem seal.
INSPECTION
When valves have been removed for inspection, reconditioning or replacement, valve springs should be tested (Fig. 46). As an example; the compression length of the spring to be tested is 38.00 mm (1.496 inch). Turn table of Tool C-647 until surface is in line with the 38.00 mm (1.496 inches.) mark on the threaded stud and the zero mark on the front. Place spring over stud on the table and lift compressing lever to set tone device. Pull on torque wrench until ping is heard. Take reading on torque wrench at this instant. Multiply this reading by two. This will give the spring load at test length. Fractional measurements are indicated on the table for finer adjustments. Refer to Engine Specifications to obtain specified height and allowable tensions. Replace springs that do not meet specifications.
INSTALLATION
CYLINDER HEAD OFF
1. Coat valve stems with clean engine oil and insert in cylinder head.
2. Install new valve stem seals.
CAUTION: If oversize valves are used, there is only one oversize valve available. The same stem seal is used on both the standard and oversize valve.
NOTE: On the high output R/T engine, the valve spring MUST be oriented properly when installed. The closely spaced spring coils should be positioned toward the cylinder head (spring seat) (Fig. 49).
3. Position valve spring and retainer on spring seat (Fig. 48) or (Fig. 49).
4. Compress valve springs only enough to install locks, taking care not to misalign the direction of compression. Nicked valve stems may result from misalignment of the valve spring compressor.
CAUTION: When depressing the valve spring retainers with valve spring compressor the locks can become dislocated. Check to make sure both locks are in their correct location after removing tool.
5. Check the valve spring installed height after refacing the valve and seat (measurement B) (Fig. 47).
Make sure measurements are taken from top of spring seat to the bottom surface of spring retainer. If height is greater than 40.18 mm (1.58 inch), install a 0.762 mm (0.030 inch) spacer under the valve spring seat to bring spring height back within specification.
6. Install rocker arms and shafts.
7. Checking dry lash. Dry lash is the amount of clearance that exists between the base circle of an installed cam and the rocker arm roller when the adjuster is drained of oil and completely collapsed. Specified dry lash is 1.17 mm (0.046 inch) for intake and 1.28 mm (0.050 inch) for exhaust. After performing dry lash check, refill adjuster with oil and allow 10 minutes for adjuster(s) to bleed down before rotating cam.
CYLINDER HEAD ON
1. Install valve stem seal assembly.
NOTE: On the high output R/T engine, the valve spring MUST be oriented properly when installed. The closely spaced spring coils should be positioned toward the cylinder head (spring seat) (Fig. 49).
2. Position valve spring and retainer on spring seat (Fig. 48) or (Fig. 49).
3. With air pressure applied in cylinder and piston at TDC, use Special Tool MD-998772A to compress valve springs, only enough to install the locks. Correct alignment of tool is necessary to avoid nicking valve stems.
4. Install the rocker arm shaft assemblies.
5. Install the cylinder head cover.