Description of Change: New cast iron valve guides and new exhaust valves with chrome plated stems are used in these commercial engines. The new threaded bore cast iron valve guides replace the former smooth bore powder metal valve guides. The new cast iron valve guide is an improvement over earlier cast iron valve guides for the following reasons:
* The cast iron material in the new valve guides is improved for greater wear resistance.
* The inner diameter of the uninstalled new guide is larger than the inner diameter of the earlier cast iron guide (9.515 mm versus 9.502 mm (.3746 in versus .3741 in) for greater hot running clearance (to reduce guide wear).
* The “teepee top” design of the new guide will reduce the amount of oil drawn into the valve stem/guide bore clearance because the oil has no place to collect where it can be fed into the clearance.
In addition to the change in the valve guide material, the exhaust valve stem will now be chrome plated for increased guide wear resistance. The new exhaust valve MUST be used with the new valve guide and the new exhaust valve may be used with the former valve guides.
Adaptable To: The new 148-7425 Valve Guide (cast iron) replaces the former 109-0390, 116-7553, and 148-7502 Valve Guides. The new 148-7455 Exhaust Valve (chrome plated stem) replaces the former 100-7861 Exhaust Valve. The former valve guides and exhaust valve are canceled. These changes are in effect with 3304B and 3306B Commercial Engines as listed below. The new valve guide and exhaust valve, when used togather, are adaptable to all 3304/B and 3306/B Commercial Engines.
* 3304B (10E5372-Up) Industrial Engines
* 3304B (9HK394-Up, 83Z10638-Up) Generator Set Engines
* 3306B (7JB11171-Up, 64Z25546-Up) Industrial Engines
* 3306B (1RS573-Up, 84Z3082-Up) Marine Engines
* 3306B (2AJ1199-Up, 8JJ411-Up, 9DJ28-Up, 9NR2566-Up, 1CZ547-Up, 85Z14237-Up) Generator Set Engines
Use the 9U-6954 Guide Collar with a 9U-7349 Driver for parts service installation of the new 148-7425 Valve Guides in the cylinder head.
SUPPLEMENT: OCTOBER 1998