31. Valve Guide Reaming/Valve and Seat Grinding

Valve Grinding and Valve Guide Inspection and Replacement

^ Tools Required
- J 37968 Valve Guide Installer
- J 37971 Valve Guide Reamer





1. Use a hole gauge, and measure the inside diameter of the valve guide bushing.
Standard Valve Guide Bushing Inside Diameter 5.485 - 5.510 mm (0.2159 - 0.2169 inch)





2. Use a micrometer, and measure the outside diameter of the valve stem.
^ Standard Intake Valve Stem Diameter 5.465 - 5.480 mm (0.2152 - 0.2157 inch)
^ Standard Exhaust Valve Stem Diameter 5.440 - 5.455 mm (0.2142 - 0.2148 inch)
3. Obtain the oil clearance of the valve guide bushing by subtracting the outside diameter measurement of the valve stem from the inside diameter measurement of the valve guide bushing.
^ Standard Intake Valve Oil Clearance 0.005 - 0.045 mm (0.0002 - 0.0018 inch)
^ Standard Exhaust Valve Oil Clearance 0.030 - 0.070 mm (0.0012 - 0.0027 inch)
^ Maximum Intake Valve Oil Clearance 0.07 mm (0.0027 inch)
^ Maximum Exhaust Valve Oil Clearance 0.09 mm (0.0035 inch)
4. If the clearance is greater than the maximum specified, replace the valve and the valve guide bushing.





5. Use a J 37968 and a hammer, and tap the valve guide bushing out of the cylinder head.





6. Use a J 37968 and a hammer, and tap the new valve guide bushing into the cylinder head.
7. Install the valve guide bushing to the specified protrusion height of 11.5 mm (0.45 inch).





8. Use a J 37971, and ream the valve guide bushing in order to obtain the standard clearance between the valve guide bushing and the valve stem.
^ Standard Intake Valve Oil Clearance 0.005 - 0.045 mm (0.0002 - 0.0018 inch)
^ Standard Exhaust Valve Oil Clearance 0.030 - 0.070 mm (0.0012 - 0.0027 inch)
^ Reconditioning the valve seats is very important.

Important: The 1.0L cylinder head has small air mixing tubes in the intake ports at the intake valves. Do not damage the tubes during valve seat reconditioning.

^ After reaming the valve-guide bores, recondition the valve seat.

Important: Because the valve guide supports and centers the valve grinder, it is essential to clean the valve guide correctly. If the valve guide requires reaming, do this first.

^ Inspect the valve seats for excessive wear and for burned spots. Valve seats may be reconditioned by grinding. If grinding results in the new seat being too wide, narrow the seat by using a 20-degree or 70-degree stone. The 20-degree stone will lower the seat, and the 70-degree stone will raise the seat.
^ The valves must seat perfectly for the engine to deliver optimum power and performance.
^ Cooling the valve heads is another important factor. Good contact between each valve and each seat in the cylinder head is necessary in order to correctly remove the heat in the head.
^ Regardless of the equipment, the valve-guide bores must be free from carbon and from dirt. The pilot will be centered in the guide.
^ The valve seats should be concentric within 0.05 mm (0.031 inch) of the total indicator reading.
^ Replace any valve that is not in serviceable condition.