See Figure 1
Valve guides should be cleaned as outlined earlier, and checked when valve stem diameter and stem-to-guide clearance is checked. Generally, if the engine is using oil through the guides (assuming the valve seals are OK) and the valve stem diameter is within specification, it is the guides that are worn and need to be replaced.
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 inside the valve guide bore is displaced and raised (forming a very fine cross-hatch pattern), thereby reducing clearance. Knurling also provides for excellent oil control. The possibility of knurling rather than replacing the guides should be discussed with a machinist.
REMOVAL & INSTALLATION
See Figures 2, 3, 4 and 5All Engines Except SD22, SD25 and VG30i
- With the cylinder head removed from the engine, and the valves removed from the head, use a drift and a hammer or press. Drive the valve guides out from the combustion chamber side toward the rocker cover side. A heated cylinder head will facilitate the operation.
- Ream the cylinder head side guide hole at room temperature. The guide hole should be 0.4719-0.4723 in. (11.989-11.996mm) for standard valves and 0.4797-0.4802 in. (12.184-12.197mm) for 0.0079 in. (0.2mm) oversize valves which are available for service.
- After heating the cylinder head to 302-392°F (150-200°C) or 302-320°F (150-160°C) on the Z24i, press the new valve guide carefully into the cylinder head. The top of the valve guide should protrude out the top of the guide hole 0.4173 in. (10.5mm).
- Ream the bore of the valve guide with the valve guide pressed into the cylinder head. The standard valve guide bore size is 0.3150-0.3157 in. (8.00-8.02mm).
- Assemble the cylinder head and install it on the engine.
- Remove the valve springs.
- Heat the cylinder head to at least 320°F (160°C), then drive out the guide using an arbor press or a hammer and drift punch.
Drive the valve guides toward the rocker arm cover side of the cylinder head.
With the valve guides removed, ream the cylinder head valve guide hole (inside diameter) to:
- Intake: 0.4400-0.4408 in. (11.176-11.196mm)
- Exhaust: 0.4793-0.4802 in. (12.174-12.197mm)
- Heat the cylinder to at least 320°F (160°C) and press the service valve guide onto the cylinder head.
Ream the valve guide (inside diameter) to:
- Intake: 0.2756-0.2763 in. (7.000-7.018mm)
- Exhaust: 0.3150-0.3157 in. (8.000-8.019mm)
- To install, use new gaskets and valve guide seals, then reverse the removal procedures.
Valve guides are not replaceable.