Description

Cummins NT 855, Big Cam IV, New Big Cam IV, 88 Big Cam IV 1989 Technical Manual

You’ve got a customer’s NT 855 that won’t hold head gaskets. You grab a torque wrench and a generic spec sheet from some forum. Then you find out the hard way that the cylinder head bolts on a Big Cam IV need a different sequence than the New Big Cam IV. That’s a blown gasket and a comeback waiting to happen. This Cummins NT 855, Big Cam IV, New Big Cam IV, 88 Big Cam IV 1989 Technical Manual ends that guesswork. It’s the same 83-page booklet Cummins put in the hands of their own techs back in ‘89. No reprints, no aftermarket condensation – just the factory rebuild and torque data direct from Columbus, IN.

Cam Follower Assembly and Injection Timing

Fixed injection timing and MVT injection timing live under the Cam Follower Assembly section. Page 0-45 spells out the rebuild specs for both. If you’re setting up a New Big Cam IV with the variable timing system, you need the exact plunger travel numbers from that page. The manual separates Fixed and MVT timing clearly – no confusion between the two. Also includes torque values for the cam follower bracket capscrews on page 0-50. I’ve seen guys use the wrong torque on those and strip the threads in the block. Don’t be that guy.

Cooling System Torque Values: Why Specs Matter

The Cooling System section lists torque values for the water pump, thermostat housing, and fan hub. A water pump that leaks after a rebuild is almost always a mis-torqued mounting bolt. The manual gives you the exact foot-pounds for each fastener. It also covers the reserve flow cooling thermostat operating temperature – page data for the thermostat housing assembly rebuild specs. If you’re working on an 88 Big Cam IV, the cooling system routing is the same but the fan hub inspection specs differ. Page 0-64 covers that.

Cylinder Block and Head Rebuild Specifications

The Cylinder Block section has rebuild specs for bore limits, deck height, and main bearing bore alignment. Torque values for the main bearing capscrews are right there. Overlooking any of those will cost you a block. The Cylinder Head section covers valve guide wear limits, seat angles, and head bolt torque sequence. The manual calls out the exact capscrew markings for head bolts – you can cross-reference with the capscrew markings chart earlier in the book. Never trust a bolt that doesn’t match the grade marking. I’ve seen aftermarket manuals skip that detail. This one doesn’t.

Does This Manual Cover the Fuel System?

Yes, but not the troubleshooting part. The Fuel Pump and Compressor Drive section gives you rebuild specs and torque values for the fuel pump drive. The Injectors section has rebuild specs for top stop injectors. Injection timing codes are listed in a separate table. If you need the full diagnostic trees, you want the Cummins NT 855 Troubleshooting Manual – 693 Pages of OEM Diagnostic Data. But for rebuild specs and torque values on fuel system components, this technical manual is the source.

Get the Right Torque Data from the Factory Source

Aftermarket manuals love to combine all Big Cam variants into one generic table. That works until you snap a capscrew because they listed the wrong torque for an 88 Big Cam IV rocker lever housing bolt. This manual separates torque values for each component – capscrew markings, pipe plug torque, cooling system, lubricating oil system, engine assembly capscrew torque values. Page references are clear. For example, the Lubricating Oil System torque values are listed right after the capacities table. You can trust these numbers. I’ve torqued thousands of bolts using these exact specs. They work.

3 Sections That Save You from a Comeback

First, the Valve and Injector Adjustments section covers crosshead adjustment, injector preload (top stop), Jacobs engine brake, and Cummins engine brake. Each adjustment has a spec and a procedure. Second, the Engine Testing section includes test specifications for horsepower and fuel rate. Third, the General Engine Specifications section gives you cooling system capacity, electrical system specs, exhaust system limits, and lubrication system data. That’s a lot of info in 83 pages. Use it.

Why This OEM Manual Beats Aftermarket Copies

This is a scanned original from 1989 – Bulletin No. 3810434-00. The page numbers match the factory printed version. The table of contents lists every subsection: Air Compressor inspection specs, Fan Hub inspection specs, Turbocharger inspection specs, Weights and Measures conversion factors, Newton-meter to foot-pound chart. Aftermarket reprints often mess up the decimal and metric conversion factors or crop out the pipe plug torque values. This copy is clean. You get the full document, including the literature order form and survey form at the end. If you need a Cummins NT 855 Service Manual for troubleshooting, or the Cummins Engine Handbook Parts Catalog for part numbers, we have those too. But for assembly and rebuild specs on the Big Cam IV family, this is the one.

FAQs

Is this manual specific to the NT 855 Big Cam IV engines?

Yes. It covers Big Cam IV, New Big Cam IV, and 88 Big Cam IV NT 855 series engines. No other engine families are included.

What torque values are in this manual?

It includes capscrew markings and torque values (U.S. Customary), cooling system torque values, cylinder block and head torque values, rocker lever housing torque, lubricating oil system torque, pipe plug torque, fuel pump and compressor drive torque, and cam follower torque values. Each section has the exact foot-pounds specified for each fastener by location.

Can I use this manual for a 1988 88 Big Cam IV engine?

Absolutely. The 88 Big Cam IV is explicitly listed in the title and foreword. The manual includes all specifications specific to that model, including injection timing codes and thermostat operating temperature for the reserve flow cooling system. If you need additional wiring diagrams or electrical system diagnostics, that information is in the General Engine Specifications section under Electrical System, but the manual does not include full wiring schematics – those are in the separate Manual Transmission or chassis service manual. For the engine itself, this is complete.

Does this manual include the camshaft specifications?

The Cam Follower Assembly section provides rebuild specs for the cam followers and injection timing adjustments. For detailed camshaft lobe profile and wear limits, refer to the Camshaft Operation guide from Cummins. The cylinder block section does include camshaft bore alignment specs.

You don’t need to guess torque values or hunt through internet forums for correct specs. This 83-page factory technical manual puts the original Big Cam IV rebuild data on your bench. Cylinder head torque, cooling system fasteners, fuel pump drive – it’s all here from the 1989 Cummins engineers. Access the Factory Manual and start the job with the right numbers.