Cummins N855 engine specs
Key bolt torques, assembly clearances, common settings, tune-up method
at Barrington Diesel Club




Cummins NTC 350 and NTC 400 Big Cam engine specs, bolt torques and a procedure of how to set your Cummins N855 at Barrington Diesel Club. We are dedicated to providing specs and technical data for diesel engines.

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Cummins N855 engine specs
Full-Load Power ratings for Industrial Cummins NTC400.
RPM 1300 1500 1800 2100
Horse Power SAE (sea level) 309 330 368 400
Power kW (sea level) 230 246 274 298
. . . . .
Torque Ft lbs 1,250 1,155 1,074 1,000
Torque Nm 1,695 1,566 1,456 1,356
. . . . .
Fuel Consumption l/hour* 60.9 65.1 72.6 78.9
Fuel Consumption US gallons/hour* 16.1 17.2 19.1 20.8
*Fuel consumption rate calculated @ 0.37 lbs/hp hour
Max Toque Ft lbs = 1250 @ 1300 rpm Max Toque Nm = 1695 @ 1300 rpm
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Physical Characteristics Cummins NTC 400 Big Cam engine
Weight 2870 Lbs 1303 Kgs
Length 59 Inches 1496 mm
Width 33.6 inches 854 mm
Height 51 inches 1293 mm
Compression Ratio 14.0 : 1
Displacement 855 Cu Inches 14.0 liter
Bore 5.5 inches 139.7 mm
Stroke 6.0 inches 152.4 mm



Selected Bolt Torques for Cummins N855 Big Cam engines

Selected Bolt Torques for Cummins N855 Big Cam engines
Torques for Main Bearings Bolt Size Ft Lbs Nm
* Mains - Step 1 3/4" UNF 100 135
. Mains - Step 2 3/4" UNF 255 345
. Mains - Step 3 3/4" UNF Loosen Loosen
* Mains - Step 4 3/4" UNF 100 135
. Mains - Final Step 3/4" UNF 255 345
. . . .
* Mains - Step 1 1" UNF 155 210
. Mains - Step 2 1" UNF 305 415
. Mains - Step 3 1" UNF Loosen Loosen
* Mains - Step 4 1" UNF 155 210
. Mains - Final Step 1" UNF 305 415
Caution: Mains are either 3/4" UNF or 1" UNF
* Lubricate with 'Copper-Slip' or International compound #2, or equivalent.
*********************
Other Selected Bolt Torques for Cummins N855 Big Cam engines
Torques for: Bolt Size Ft Lbs Nm
Con Rod Bolts / Big Ends - Step 1 7/16 UNF 75 100
Con Rod Bolts / Big Ends - Step 2 7/16 UNF 150 200
Con Rod Bolts / Big Ends - Step 3 7/16 UNF Loosen Loosen
Con Rod Bolts / Big Ends - Step 4 7/16 UNF 30 40
Con Rod Bolts / Big Ends - Step 5 7/16 UNF 75 100
Con Rod Bolts / Big Ends - Final Step 3/8 UNF 150 200
. . . .
Cylinder head - Step 1 3/4 UNF 25 34
Cylinder head - Step 2 3/4 UNF 100 136
Cylinder head - Step 3 3/4 UNF 200 270
Cylinder head - Final Step 3/4 UNF 300 407
. . . .
Injector Hold-Down cap screws - Step 1 . 4 5
Injector Hold-Down cap screws - Step 2 . 8 11
Injector Hold-Down cap screws - Step 3 . 12 16
. . . .
Rocker Housing . 75 100
Jake's Housing . 60 80

OBC (Outer Base Circle) Method for setting valves and injectors when standard PTD Injectors are fitted:

Image for the Timing indicator on the gear case
Common Settings Cummins NTC 855 Big Cam engine
Set Nm Inch lb
Injectors 8.0 72
Set mm Inches
Valves - Inlet (cold) 0.36 0.014
Valves - Exhaust (cold) 0.69 0.027

OBC (Outer Base Circle) Method for setting valves and injectors when standard PTD injectors are fitted.
Image of a Typical PTD 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 #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.



Settings for Cummins NTC 855 Big Cam engine when top-stop injectors are fitted.

Image of the Timing indicator on the gear case Image of a TopStopInjector

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.
The following table gives the setting order for top-stop injectors:

Image of a TopStopInjector

Top-Stop setting order for valves and injectors for Cummins NTC 855 engines
Mark When valves of cyl # closed Set Valves of cyl # Set Injector of cyl #
A 5 5 3
B 3 3 6
C 6 6 2
A 2 2 4
B 4 4 1
C 1 1 5

Settings for Cummins NTC 855 Big Cam engine when top-stop injectors are fitted.
Set Nm Inch lb
Injectors 0.7 6.0
Set mm Inches
Valves - Inlet (cold) 0.28 0.011
Valves - Exhaust (cold) 0.58 0.023

Standard Sizes and useful clearances Cummins N855 Big Cam engine.
Part New Min inches New Max inches Limits inches New Min - mm New Max - mm Limits - mm
Con Rod - Crankpin bore 3.3157 3.3157 . 84.2187 84.2187 .
Con Rod - ID Small End Bush 2.0010 2.0015 2.0022 50.8254 50.8381 50.8559
Con Rod - Length center to center 11.998 12.000 . 304.75 304.80 .
Crankshaft end float 0.007 0.017 0.022 0.18 0.43 0.56
Crankshaft Big end Std Diameter 3.1235 3.1250 3.1220 79.337 79.375 79.299
Crankshaft Mains Std Diameter 4.4985 4.5000 4.4975 114.262 114.300 114.237
Cyl liner protrusion 0.003 0.006 . 0.076 0.152 .
Cyl Liner - ID, without Lubrite® coating 5.4995 5.5010 5.5050 139.687 139.725 139.827
Piston skirt diameter 5.487 5.488 5.483 139.37 139.40 139.27
Piston pin bush ID 2.0010 2.0015 2.0022 50.825 50.838 50.856
Ring gap - #1 compression 0.023 0.033 . 0.58 0.84 .
Ring gap - #2 & 3 compression 0.019 0.029 . 0.48 0.74 .
Ring gap - oil rings 0.010 0.025 . 0.25 0.64 .

Common operating conditions.
Item Condition
Altitude deration Turbo 1.5%, Naturally aspirated 3%, for every 300 m or 1000 ft
Firing Order 153624
Speed full load max Commonly at 2100 rpm
Speed no load max Commonly at 2400 rpm
Speed at idle Commonly between 580-620 rpm


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Phone: +27 72 754 4660    *    Fax: 086 544 1447
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Page Revision #16 April 2013

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