LONG BLOCK 20R3652 - Caterpillar

Diesel Engines Except 3500 And 3600 Family Of EnginesReference: Service Magazine, October 28, 1985, Page 5, "Comparison Of Fuel Timing Tolerances For Field Settings". Changes which were announced earlier in the above reference article have now been made in the OT microfiche. They are summarized as follows:
...Static (or pin) timing tolerance is now 2°.
...For all engines with rated load rpm above 1200, "TIMING DEGREES AT LOW IDLE" is changed to "TIMING DEGREES AT REF (reference) RPM" and a speed of 1000 rpm is indicated. (Dynamic fuel timing measurements using the 6V3100 Timing Indicator Group are not recommended at speeds below 1000 rpm.)
In the recently revised 3406B Diesel Truck Engine Service Manual, Form SEBR0544-01, the term "Base RPM" is used. This is the same as "Ref RPM"....Tolerance for "TIMING DEGREES AT REF RPM", "TIMING DEGREES AT START RPM" and "TIMING DEGREES AT MID RPM" is now 1.5°.
...Tolerance for "TIMING DEGREES AT STOP RPM" is now 2.5°. If engine has no timing advance mechanism, the tolerance is 1.5°.
...Timing advance specifications for 3406B New Scroll engines ONLY now include 0.2° port effect advance per 100 rpm. (All other engines are 0.1° per 100 rpm.)
..."OCCURRENCE NO." is a new data field added under the timing advance group number. This will be useful information in the near future when PRE-PLOTTED timing advance specifications are available to dealer service personnel.
...The required QUANTITIES of each spring and spacer in a torque control group are now specified.
These changes coincide with the 030386 OT Fiche issue date.