ARMY TM 9-2815-255-24
AIR FORCE TO 38G1-95-2
MARINE CORPS TM 2815-24/4
Combustion face surface finish (surface grind only) should be 75AA minimum to 130AA maximum.
Maximum wave depth should be 0.0005 inch (0.012 mm).
Clean and measure valve guides as follows: (1) Use a plastic brush to clean valve guides before inspection or
A few drops of light oil or kerosene will help to fully clean the guide.
Using a telescopic gage, measure valve guides for wear.
ID of valve guide bore in a new cylinder head is 0.312 to 0.313 inch (7.912 to 7.938 mm).
New guide-to-valve stem clearance is 0.002 to 0.004 inch (0.05 to 0.10 mm).
Maximum permissible clearance is 0.006 inch (0.015 mm).
If valve guide oil clearance is more than maximum allowable, but not more than 0.008 inch (0.20 mm),
valve guides can be knurled. Refer to step k.
If valve guide oil clearance is over 0.008 inch (0.20 mm), intake and exhaust valves with oversize stems
are available. Valve guides can be knurled and then reamed to fit oversize valve stems. Oversize valve
stems are available for service in 0.015 inch (0.38 mm) or 0.030 inch (0.76 mm) sizes.
Knurl, thread, and ream valve guides as follows:
Always knurl valve guides before threading. Hand ream after threading to assure proper valve
Use knurling tool set to knurl valve guides. Use tool set exactly as directed by the manufacturer.
After knurling, thread full circumference of valve guides for entire length of bore using a 5/1624NF
modified internal thread tap with a major OD of 0.317 to 0.320 inch (8.05 to 8.09 mm).
After threading, hand ream valve guide to finished size to provide specified stem-to-guide clearance. A
0.3105 inch (7.887 mm) OD pin must pass freely through entire length of bore after reaming.
Clean and inspect valve seats as follows:
Use an electric hand drill with end brush to remove all carbon on valve seats.
Check seats for cracks, pits, or excessive wear.
Check entire combustion face for rust, scoring, pitting, or cracks.
Grind valve seats to obtain correct valve recess and valve head-to-seat contact angle. Refer to
paragraph 3-34.2. for recess inspection. Be sure valve guide bores are clean and serviceable
(refer to step j) before grinding valve seats to maintain valve guide bore-to-seat runout. Always
maintain sure footing and a balanced position. Give the work your undivided attention,
otherwise engine performance will be poor.
Always keep work area clean when grinding valve seats.