The valve guides used in these engines are integral with the cylinder head, that is, they cannot be replaced.
Refer to the previous Valves Removal and Installation to check the valve guides for wear.
Valve guides are most accurately repaired using the bronze wall rebuilding method. In this operation, threads are cut into the bores of the valve guide and bronze wire is turned into the threads. The bronze wall is then reamed to the proper diameter. This method is well received for a number of reasons:
- It is relatively inexpensive
- It offers better valve lubrication (the wire forms channels which retain oil)
- It offers less valve friction
- It preserves the original valve guide-to-seat relationship.
Another popular method of repairing valve guides is to have the guides knurled. The knurling entails cutting action raises metal off of the guide bore which actually narrows the inner diameter of the bore, thereby reducing the clearance between the valve guide bore and the valve stem. This method offers the same advantages as the bronze wall method, but will generally wear faster.
Another method of repairing the guides is to ream the bores and install oversize valves.
Either of the above services must be performed by a professional machine shop which has the specialized knowledge and tools necessary to perform the service.