Usage:
G342 Engines
Reference: "New Inlet And Exhaust Valves And Valve Guides Have Tighter Fit To Prevent Corrosion And Guide Wear", Service Magazine, June 29, 1981, Page 12 and its Supplement, Service Magazine, August 31, 1981, Page 8.
Description of Change: New inlet and exhaust valves and valve guides are used in G342 Engines.
The new valves have smaller 9.441 mm (.3717") diameter stems. The new valve guide has a counterbore, and it can be used with either an inlet or exhaust valve.
Used together, the new valves and valve guides have a tighter fit than the former valves and valve guides. The tighter fit keeps combustion gases out of the area between the valves and valve guides.
Formerly, a valve with a 12.7 mm (.50") diameter stem was used. It was possible for combustion gases to get in between the valves and guides. These gases caused corrosion which then caused the guides to wear rapidly. The rate of corrosion and wear is increased when high sulfur fuel is used.
Adaptable To: The new parts are in effect with Serial Number 71B3163. The parts shown in the chart, when used together, are adaptable to all earlier G342 Engines.
The guides must have 0.038 mm (.0015") clearance. Some guides will have to be machined; other guides will not. Measure the clearance about 115 mm (4.50") from the keeper end.
| NOTICE |
|---|
The clearance between the valve and the valve guide has an effect on the service life of the valve guide. It is necessary to have the correct clearance to stop the movement of combustion gases and the corrosion and wear which are the result.
|
Use the 1P7451 Valve Guide Honing Group and 5P8615 Honing Oil to get the final clearance if necessary. The complete procedure for use of the 1P7451 Valve Guide Honing Group is given in Special Instruction, Form No. SMHS7526.
Use the 1P7430 Valve Guide Driver Assembly and the 5P1727 Valve Guide Driver Bushings to install the guides to the correct depths. The tops of the guides must be 42.93 ± 0.50 mm (1.690 ± .019") above the machined surface around the valve guides holes.
If desired, two service head assemblies are available. The 5N8505 Cylinder Head Assembly is for use with valves which have 9.441 mm (.3717") diameter stems. The 8N6001 Cylinder Head Assembly is for use with valves which have 12.7 mm (.50") diameter stems.