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BigCam Cummins N855 injector and valve settings



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BigCam Cummins N855 injector and valve settings


Tune up information for owners and repairers of Cummins N855 engines

Cummins BigCam setting valves and PTD Injectors:

Timing Indicator on Cummins N855 gear casing a Typical PTD Injector
Cummins NTC 855 Big Cam engine
OBC (Outer Base Circle)
common settings

Torque Injectors
8.0 Nm, 72 inch.lb

Inlet valves, cold
0.36 mm, 0.014 inch

Exhaust valves, cold
0.69 mm, 0.027 inch


OBC (Outer Base Circle) Method for setting valves and injectors when standard PTD injectors are fitted.
Loosen all valves and injectors so that the engine turns freely while keeping the push rods in place.

Rotate engine clockwise until the "A, OR 1-6 VS" timing mark on the accessory drive pulley is aligned with the timing indicator on the front gear case, as shown in the illustration. Set the injector and valves on cylinder #1 or #6 as required.
Mark the rockers of the set valves and injector with a white pen to keep tabs on what you've done.
Rotate the engine to the next timing mark and set the appropriate valves and injector, proceed until all valves and injectors are set. Two engine revolutions are required to set all the valves and injectors.



Setting Cummins NTC 855 Big Cam top-stop injectors.

Timing Mark on A
When Valves on #5 are closed
Set Vales #5
Set Injector #3

Timing Mark on A
When Valves on #2 are closed
Set Vales #2
Set Injector #4

Timing Mark on B
When Valves on #3 are closed
Set Vales #3
Set Injector #6

Timing Mark on B
When Valves on #4 are closed
Set Vales #4
Set Injector #1

Timing Mark on C
When Valves on #6 are closed
Set Vales #6
Set Injector #2

Timing Mark on C
When Valves on #1 are closed
Set Vales #1
Set Injector #5

Top Stop Injectors
common settings

Torque Injectors
0.7 Nm, 6.0 inch.lb

Inlet valves, cold
0.28 mm, 0.011 inch

Exhaust valves, cold
0.58 mm, 0.023 inch


Timing Indicator on Cummins N855 gear casing a Top-Stop Injector

Use the IBC (inner base circle) method to set NTC,s when top-stop injectors are fitted. Essentially this means that the setting points, setting order and setting values for the valves and injectors are different from the OBC method described above, but you still use the marks on the accessory drive pulley and the gear case for orientation.
Note: the very low injector torque might require a special torque wrench to achieve. Do not exceed the torque. You should be able to just rotate the pin, rocker to injector, with your fingers after torquing the injector.


Loosen all valves and injectors so that the engine turns freely while keeping the push rods in place.

Rotate engine clockwise until the "A, OR 1-6 VS" timing mark on the accessory drive pulley is aligned with the timing indicator on the front gear case, as shown in the illustration. Set the injector and valves on cylinder # according to the table below.
Mark the rockers of the set valves and injector with a white pen to keep tabs on what you've done.
Rotate the engine to the next timing mark and set the appropriate valves and injector, proceed until all valves and injectors are set. Two engine revolutions are required to set all the valves and injectors.

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