Usage:
D353, D379, D398, D399 Industrial And Marine Engines
- SUPPLEMENT: 09/16/81
ENGINES NEWS, APRIL 1, 1981, PAGE 2.
In the article "New Inlet And Exhaust Valves And Valve Guides Have Tighter Fit To Prevent Corrosion And Guide Wear," the diameter of the stem on the new valve is wrong. Change the first sentence in the second paragraph to:
"The new valves have smaller, 9.441 mm (.3717") diameter stems."
--------------- END SUPPLEMENT ---------------
Description of Change: New inlet and exhaust valves and valve guides are used in the above engines.
The new valves have smaller, 9.525 mm (.375") diameter stems. The new valve guides have thread-like grooves on their inside diameters.
Used together, the new valves and valve guides have a tighter fit than the former valves and 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 (.500") 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.
Adaptable To: The new parts are in effect with the Serial Numbers given in Chart A. The new parts, used together, are adaptable to all earlier engines shown in Chart A.
Chart B has the parts needed. Chart C has the service head assemblies which are available with the new valves and guides.
The guides must have 0.038 mm (.0015") clearance. Some guides will have to be machined; other guides will not. For clearance checks, the valve stem is to be measured about 115 mm (4.50") from the keeper end.
| NOTICE |
|---|
The clearance between the valve and 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 results.
|
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 2P2313 Valve Guide Driver Bushing to install the valve guides to the correct depth in heads. For those shops that do not have these tools, the tops of the valve guides must be 44.45 ± 0.50 mm (1.75 ± .019") above the machined surface around the valve guide hole.