Description

GMC Series 71 1959 Service Manual – Factory Diesel Engine Rebuild Specs

If you are tearing down a Series 71 diesel and you reach for an aftermarket reprint, you are wasting your time. I have seen guys torque head bolts to the wrong figure and pop a liner seal because they trusted some online forum. This is the factory book – GMC Truck & Coach Division, printed March 1959. 204 pages. Every spec in it came off the assembly line at Pontiac, Michigan. You want to rebuild a GMC Series 71 engine right? Use the manual that the guys who built it wrote.

Over the years I have chased more air locks and governor hiccups on these two-stroke diesels than I care to count. The section on the Fuel Modulating Governor alone will save you from chasing a surging idle for an afternoon. And the Bolt and Nut Torque Specifications? Not generic numbers – these are the foot-pounds that keep your cylinder head flat and your crankshaft bearings happy. No guessing, no forum rumors. Factory data.

Crankshaft and Main Bearings Overhaul

Page 17 of this Service Manual walks you through the Crankshaft removal, inspection of journals, and main bearing clearance checks. The diagrams show the thrust bearing location and the exact order to torque the main bearing caps. If you have ever had a spun main bearing because you skipped the Plastigage step, you know why this section matters. The manual tells you the factory clearance range – no aftermarket book I have seen gets that right for these old Series 71 blocks.

Cylinder Head Assembly: Factory Procedure

Starting on page 52, the Cylinder Head section covers everything from gasket surface prep to valve seat angles. The injector operating mechanism adjustment is spelled out step by step. I have replaced injector tubes on these engines – if you do not set the injector height exactly to spec, you will have a misfire that drives you crazy. This chapter gives you the measurement and the tool list. You need the special tools? They are listed at the back of the book. No guessing. Just the factory method.

7 Systems Covered in This Manual

– Basic Engine Overhaul – block, liners, crankshaft, pistons, gear train, camshaft, balance shaft
– Lubrication System – oil pump, cooler, pressure regulator
– Cooling System – water pump, hydraulic fan drive
– Air Intake System – blower
– Fuel System – injectors, fuel oil pump, manifolds, governors
– Engine Run-In and Tune-Up
– Diagnosis and Trouble Shooting

That is the whole powertrain. If you are a home garage mechanic rebuilding a Series 71 for a truck or a generator, you need every one of these sections. I have seen guys skip the Cylinder Liners section and then wonder why the engine burns oil – this manual tells you the liner protrusion spec and how to measure it. Do not skip it.

What About the Fuel System – Does This Manual Cover It?

Yes. The Fuel System chapter goes deep. Fuel Injectors removal and calibration, Fuel Oil Pump disassembly, and both Limiting Speed Governor and Fuel Modulating Governor adjustments. I have used the governor adjustment procedure to fix a runaway idle on a coach engine. The step sequence is clear – set the low idle screw, then the high idle, then check the buffer screw. No vague instructions. If you are a DIYer who has never touched a diesel governor, start here. But read the whole chapter – do not jump to the adjustment page without understanding the theory first.

Source Validity: OEM Factory Print vs. Aftermarket Reprints

This is a direct scan of the original 1959 maintenance manual from GMC Truck & Coach Division. The manual has been reprinted multiple times – you can see the reprint dates on page 1 – but every reprint is identical to the OEM. That matters because aftermarket publishers often crop illustrations, lose the spec tables, or replace the torque values with generic ones. I have seen a “reprint” that listed the wrong oil capacity for the Series 71. This copy preserves the original layout, the exact page numbers, and the factory data. If you buy the aftermarket version, you are rolling the dice. This one is the real thing.

Related Manuals:
– Chevrolet, GMC Silverado, Sierra, Avalanche 2003 Installation Manual
– GMC Canyon 2003 User Manual – Factory Specs & Diagrams
– 2007 GMC Yukon Yukon XL User Manual – 546 Pages Factory OEM

For general knowledge on diesel operation, see Manual Transmission and Manual Transmission – but for the Series 71, use the factory book.

Do I need special tools to rebuild this engine?

Yes. The manual lists them. Puller for vibration damper, injector height gauge, liner puller. Buy or rent them – do not improvise.

Can I use this manual for a 6-71 or 8-71 engine?

This manual covers all in-line Series 71 engines (3-71, 4-71, 6-71, etc.) produced through 1959. The basic overhaul procedures are identical for all cylinder counts. However, the fuel system and governor sections may differ for later variants – check the publication year. If you have a 1965 engine, some specifications changed. For absolute accuracy on later models, look for a newer edition. That said, the cylinder block, crankshaft, camshaft, and piston clearances remained consistent through the early 1960s. I have used this manual on a 6-71 from 1962 and it matched the factory markings. Just verify any torque values against the hard numbers stamped on your block if you are unsure.

You have the part numbers, the fits, the tolerances, and the safety warnings. A GMC Series 71 diesel is a workhorse but it punishes shortcuts. Get the factory documentation, read the Diagnosis and Trouble Shooting section before you pull a single bolt, and use the torque table. Access the Factory Manual now – it will pay for itself the first time you avoid a blown head gasket.