REMOVAL & INSTALLATION
Except the 6-251 Gasoline and 6-243 Diesel
Worn valve guides can, in most cases, be reamed to accept a valve with an oversized stem. Valve guides that are not excessively worn or distorted may, in some cases, be knurled rather than reamed. However, if the valve stem is worn reaming for an oversized valve stem is the answer since a new valve would be required.
Knurling is a process in which metal is displaced and raised, thereby reducing clearance. Knurling also produces excellent oil control. The possibility of knurling instead of reaming the valve guides should be discussed with a machinist.6-251 Engine
These guides are replaceable. Special tools are required.
- Drive the guides down into the tappet chamber using a guide driver. Drivers should be 7 / 16 in. (11.1mm) and 11 / 32 in. (8.7mm).
- If the guides don't clear the chamber, break off the lower end with a hammer and drift then drive out the remaining piece.
- Lubricate the new guides, insert them into position from above and drive them into place. Intake valve guides are installed with the counterbore down; exhausts with the counterbore up. Top of guide-to-block height must be 0.875 in. (22.2mm).
See Figure 1
These guides are replaceable.
- Press out the old guide using tool #31691-10500 or equivalent.
- Press the new guide into the head using tool #31691-00800 or equivalent. Installed height, above the head, should be 0.69-0.72 in. (17.7-18.3mm).