AIR CLEANER GP 3496259 - Caterpillar

All EnginesSUPPLEMENT: 01/00/86ENGINE NEWS, NOVEMBER 1985, PAGE 1, "COMPARISON OF FUEL TIMING TOLERANCES FOR FIELD SETTINGS".Add a note to this article that it does not apply to 3500 or 3600 Series Engines because they have unit fuel injectors. None of the three timing methods discussed in the article is used on these engines.
Also, in the third line of the section, "Tolerances For All 3406B Engines", replace the word "tolerance" with "advance".
--------------- END SUPPLEMENT ---------------Reference: "Engine Information Plate Contains More Data; Use Of Performance Specifications" in this same issue.This topic applies to any engine with any type of Caterpillar fuel system. Fuel timing can be done by pin timing on the engine, fuel flow timing, or engine dynamic timing. Each of the three methods will result in a slightly different timing setting. This can be confusing to dealers and users, particularly if the fuel system parts are excessively worn. For example, you can expect a 2° difference between the static fuel flow setting method and engine dynamic timing with excessively worn parts.
Engines such as D353, D379, D398 and D399 Engines, that have had lifter settings adjusted on the engine, can be timed very accurately with the pin method. However, if the lifters are worn, the fuel flow method is more accurate. But, since worn lifters usually mean wear in the plunger scroll area, engine dynamic timing is really the best of the three methods. This method accounts for wear in all the fuel system parts. This may be the reason for possibly a 2° variation between the static fuel flow setting method and engine dynamic timing method.
In order to allow for the expected tolerances on fuel system parts with little or no wear, the following timing tolerances are to be used in place of previous tolerances in the field:
... Pin timing. This is changed from 1° to 2°, which is usually equal to one-half of the diameter of the timing bolt hole depending on engine model. Note this change in the Service Manual Specifications. Pin timing is recommended only to install the injection pump housing on the engine, although in some cases, it can provide acceptable complete engine timing.... Static fuel flow method. This tolerance remains 1°. Change the Testing and Adjustment Module where stated otherwise in the Service Manuals.... Dynamic (engine running) fuel timing method using the 6V3100 Timing Indicator Group. This tolerance is now 1.5°. This is due to the various tolerances from flywheels, flywheel housings, etc. which the indicator uses as part of its measurement. Refer to Special Instruction SEHS7742-03 and note this change on Page 21 under the topic "Timing Tolerances". Add this also to the Testing and Adjusting Module for the Service Manual on 3406B Engines.... For all engines except those with a full load rpm of 1200 or less, do not measure dynamic timing below 1000 rpm. Unstable readings are often obtained below 1000 rpm. Presently, the 0T Microfiche on fuel settings shows fuel timing for low idle. This