Removing the Cylinder Head
See the engine service procedures earlier in this section for details concerning specific engines.Identifying the Valves
Invert the cylinder head, and number the valve faces front to rear, using a permanent felt-tip marker.Removing the Rocker Arms
Remove the rocker arms with shaft(s) or balls and nuts. Wire the sets of rockers, balls and nuts together, and identify according to the corresponding valve.Removing the Valves and Springs
Using an appropriate valve spring compressor (depending on the configuration of the cylinder head), compress the valve springs. Lift out the keepers with needlenose pliers, release the compressor, and remove the valve, spring, and spring retainer. See the engine service procedures earlier in this section for details concerning specific engines.Checking the Valve Stem-to-Guide Clearance
Clean the valve stem with lacquer thinner or a similar solvent to remove all gum and varnish. Clean the valve guides using solvent and an expanding wire-type valve guide cleaner. Mount a dial indicator so that the stem is at 90° to the valve stem, as close to the valve guide as possible. Move the valve off its seat, and measure the valve guide-to-stem clearance by rocking the stem back and forth to actuate the dial indicator. Measure the valve stems using a micrometer, and compare to specifications, to determine whether stem or guide wear is responsible for excessive clearance.
Consult the Specifications tables earlier in this section.De-Carboning the Cylinder Head and Valves
Chip carbon away from the valve heads, combustion chambers, and ports, using a chisel made of hardwood. Remove the remaining deposits with a stiff wire brush.
Be sure that the deposits are actually removed, rather than burnished.Hot-Tanking the Cylinder Head (Cast Iron Heads Only)
Have the cylinder head hot-tanked to remove grease, corrosion, and scale from the water passages.
In the case of overhead cam cylinder heads, consult the operator to determine whether the camshaft bearings will be damaged by the caustic solution.Degreasing the Remaining Cylinder Head Parts
Clean the remaining cylinder head parts in an engine cleaning solvent. Do not remove the protective coating from the springs.Checking the Cylinder Head for Warpage
Place a straight-edge across the gasket surface of the cylinder head. Using feeler gauges, determine the clearance at the center of the straightedge. If warpage exceeds .003" in a 6" span, or .006" over the total length, the cylinder head must be resurfaced.
If warpage exceeds the manufacturer's maximum tolerance for material removal, the cylinder head must be replaced.
When milling the cylinder heads of V-type engines, the intake manifold mounting position is altered, and must be corrected by milling the manifold flange a proportionate amount.Knurling the Valve Guides
*Valve guides which are not excessively worn or distorted may, in some cases, be knurled rather than replaced. Knurling is a process in which metal is displaced and raised, thereby reducing clearance. Knurling also provides excellent oil control. The possibility of knurling rather than replacing valve guides should be discussed with a machinist.Replacing the Valve Guides
Valve guides should only be replaced if damaged or if an oversize valve stem is not available.
See the engine service procedures earlier in this section for details concerning specific engines. Depending on the type of cylinder head, valve guides may be pressed, hammered, or shrunk in. In cases where the guides are shrunk into the head, replacement should be left to an equipped machine shop. In other cases, the guides are replaced using a stepped drift (see illustration). Determine the height above the boss that the guide must extend, and obtain a stack of washers, their I.D. similar to the guide's O.D., of that height. Place the stack of washers on the guide, and insert the guide into the boss.
Valve guides are often tapered or beveled for installation.
Using the stepped installation tool (see illustration), press or tap the guides into position. Ream the guides according to the size of the valve stem.Replacing Valve Seat Inserts
Replacement of valve seat inserts which are worn beyond resurfacing or broken, if feasible, must be done by a machine shop.Resurfacing (Grinding) the Valve Face
Using a valve grinder, resurface the valves according to specifications given earlier in this section.
A minimum margin of 1 / 32 " should remain after grinding the valve. The valve stem top should also be squared and resurfaced, by placing the stem in the V-block of the grinder, and turning it while pressing lightly against the grinding wheel.
Do not grind sodium filled exhaust valves on a machine. These should be hand lapped.Resurfacing the Valve Seats Using Reamers or Grinder
Select a reamer of the correct seat angle, slightly larger than the diameter of the valve seat, and assemble it with a pilot of the correct size. Install the pilot into the valve guide, and using steady pressure, turn the reamer clockwise.
Remove only as much material as necessary to clean the seat. Check the concentricity of the seat (following). If the dye method is not used, coat the valve face with Prussian blue dye, install and rotate it on the valve seat. Using the dye marked area as a centering guide, center and narrow the valve seat to specifications with correction cutters.
When no specifications are available, minimum seat width for exhaust valves should be 5 / 4 ", intake valves 1 / 16 ".
After making correction cuts, check the position of the valve seat on the valve facing using Prussian blue dye.
To resurface the seat with a power grinder, select a pilot of the correct size and coarse stone of the proper angle. Lubricate the pilot and move the stone on and off the valve seat at 2 cycles per second, until all flaws are gone. Finish the seat with a fine stone. If necessary the seat can be corrected or narrowed using correction stones.Checking the Valve Seat Concentricity
Coat the valve face with Prussian blue dye, install the valve, and rotate it on the valve seat. If the entire seat becomes coated, and the valve is known to be concentric, the seat is concentric.
*I Install the dial gauge pilot into the guide, and rest of the arm on the valve seat. Zero the gauge, and rotate the arm around the seat. Run-out should not exceed .002".Lapping the Valves
Valve lapping is done to ensure efficient sealing of resurfaced valves and seats.
Invert the cylinder head, lightly lubricate the valve stems, and install the valves in the head as numbered. Coat valve seats with fine grinding compound, and attach the lapping tool suction cup to a valve head.
Moisten the suction cup.
Rotate the tool between the palms, changing position and lifting the tool often to prevent grooving. Lap the valve until a smooth, polished seat is evident. Remove the valve and tool, and rinse away all traces of grinding compound.
Fasten a suction cup to a piece of drill rod, and mount the rod in a hand drill. Proceed as above, using the hand drill as a lapping tool.
Lift the tool and change direction of rotation often.Checking the Valve Springs
Place the spring on a flat surface next to a square. Measure the height of the spring, and rotate it against the edge of the square to measure distortion. If spring height varies (by comparison) by more than 1 / 16 " or if distortion exceeds 1 / 16 ", replace the spring.
In addition to evaluating the spring as above, test the spring pressure at the installed and compressed (installed height minus valve lift) height using a valve spring tester. Springs used on small displacement engines (up to 3 liters) should be ;mp 1 lb. of all other springs in either position. A tolerance of ;mp 5 lbs. is permissible on larger engines.Installing the Valves
See the engine service procedures earlier in this section for details concerning specific engines.
Lubricate the valve stems, and install the valves in the cylinder head as numbered. Lubricate and position the seals (if used) and the valve springs. Install the spring retainers, compress the springs, and insert the keys using needlenose pliers or a tool designed for this purpose.
Retain the keys with wheel bearing grease during installation.Installing Valve Stem Seals
Due to the pressure differential that exists at the ends of the intake valve guides (atmospheric pressure above, manifold vacuum below), oil is drawn through the valve guides into the intake port. This has been alleviated somewhat since the addition of positive crankcase ventilation, which lowers the pressure above the guides. Several types of valve stem seals are available to reduce blow-by. Certain seals simply slip over the stem and guide boss, while others require that the boss be machined. Recently, Telfon guide seals have become popular. Consult a parts supplier or machinist concerning availability and suggested usages.
When installing seals, ensure that a small amount of oil is able to pass the seal to lubricate the valve guides; otherwise, excessive wear may result.Checking Valve Spring Installed Height
Measure the distance between the spring pad the lower edge of the spring retainer, and compare to specifications. If the installed height is incorrect, add shim washers between the spring pad and the spring.
Inspecting the Rocker Shaft(s) and Rocker Arms
Remove the rocker arms, springs and washers from rocker shaft.
Lay out parts in the order as they are removed.
Inspect rocker arms for pitting or wear on the valve contact point, or excessive bushing wear. Bushings need only be replaced if wear is excessive, because the rocker arm normally contacts the shaft at one point only. Grind the valve contact point of rocker arm smooth if necessary, removing as little material as possible. If excessive material must be removed to smooth and square the arm, it should be replaced. Clean out all oil holes and passages in rocker shaft. If shaft is grooved or worn, replace it. Lubricate and assemble the rocker shaft.Inspecting the Pushrods
Remove the pushrods, and, if hollow, clean out the oil passages using fine wire. Roll each pushrod over a piece of clean glass. If a distinct clicking sound is heard as the pushrod rolls, the rod is bent, and must be replaced.
The length of all pushrods must be equal. Measure the length of the pushrods, compare to specifications, and replace as necessary.Inspecting the Valve Lifters
Remove lifters from their bores, and remove gum and varnish, using solvent. Clean walls of lifter bores. Check lifters for concave wear as illustrated. If face is worn concave, replace lifter, and carefully inspect the camshaft. Lightly lubricate lifter and insert it into its bore. If play is excessive, an oversize lifter must be installed (where possible). Consult a machinist concerning feasibility. If play is satisfactory, remove, lubricate, and reinstall the lifter.Testing Hydraulic Lifter Leak Down
Submerge lifter in a container of kerosene. Chuck a used pushrod or its equivalent into a drill press. Position container of kerosene so pushrod acts on the lifter plunger. Pump lifter with the drill press, until resistance increases. Pump several more times to bleed any air out of lifter. Apply very firm, constant pressure to the lifter, and observe rate at which fluid bleeds out of lifter. If the fluid bleeds very quickly (less than 15 seconds), lifter is defective. If the time exceeds 60 seconds, lifter is sticking. In either case, recondition or replace the lifter. If lifter is operating properly (leak down time 15-60 seconds), lubricate and install it.