Mitsubishi Diesel Engines SS-series description of the catalogue:

This service manual is written to familiarize you with the maintenance of your S4S and S6S Diesel Engine. If the engine is carefully maintained it will deliver a long productive life and efficient performance marked by power and economy.
Before you attempt to inspect, disassemble, or repair the engine, read this manual carefully to learn more about the engine and how to care for it properly. All descriptions, illustrations, specifications and serial numbers in this manual are effective as of the date printing of this manual.
The information contained in this manual applies to the engine model produced at the time of publication.
It should be noted that specifications and design may change due to improvements made thereafter.