International D312 Specifications
| Engine Model: International Harvester D312 |
| Engine Type: 4-cycle inline 6-cylinder naturally aspirated liquid-cooled diesel |
| Total Displacement: 312 cu.in (5.1 L) |
| Rated Engine Power: 75 Hp (56 kW) at 2000 rpm |
| Fuel System Type: Direct fuel injection |
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The International Harvester D312 is a
six-cylinder, four-stroke diesel engine engineered for reliable service
in agricultural and light industrial equipment. As a member of
International Harvester's "300 series" engine family, it delivers
smooth, balanced power from its inline configuration. The engine
utilizes a direct injection fuel system, promoting fuel efficiency and
robust torque production.
Its construction emphasizes durability with a deep-skirt block,
replaceable wet cylinder liners, and a gear-driven camshaft. Designed
for sustained operation under load, the D312 provides dependable
performance in mid-sized tractors, where its six-cylinder smoothness and
direct injection responsiveness were valued for both drawbar work and
power-take-off applications.
Engine Type: In-line, six-cylinder, four-stroke, liquid-cooled diesel.
Combustion System: Direct injection.
Aspiration: Naturally aspirated.
Firing Order: 1-5-3-6-2-4.
Rotation (viewed from flywheel): Counter-clockwise.
Displacement: 312 cubic inches (5.11 liters).
Bore: 3.875 inches (98.4 mm).
Stroke: 4.410 inches (112.0 mm).
Compression Ratio: 17.0 to 1.
Rated Power Output: 75 gross Hp (56 kW) at 2000 rpm.
Governed Speed: 2000 rpm.
Weight (dry): 1100 lbs (499 kg).
The cylinder block is a high-strength gray iron casting of deep-skirt
design, providing a rigid foundation for the crankshaft and rotating
assembly. It employs replaceable wet-type cylinder liners. These
precision-machined alloy iron liners are inserted into the block bores
and sealed at the top by a composite or copper gasket and at the bottom
by synthetic rubber O-rings.
This wet-sleeve construction facilitates overhaul and permits cylinder
reconditioning through liner and piston replacement without machining
the parent block material. The crankshaft is supported by seven main
bearings, ensuring stable crankshaft alignment and reduced vibration.
Main bearing caps are manufactured from nodular iron and secured with
two vertical bolts per cap. The block incorporates a comprehensive
network of internal oil galleries and coolant passages surrounding each
liner.
The cylinder head is a single-piece cast iron component. It is designed
for direct injection, with individual intake and exhaust ports and
vertically mounted fuel injectors for each cylinder. The head uses a
crossflow layout.
Valve Arrangement: Overhead valves (OHV), actuated by pushrods and
rocker arms.
Valves per Cylinder: Two (one intake, one exhaust).
Intake Valve Head Diameter: 1.75 inches (44.5 mm).
Exhaust Valve Head Diameter: 1.50 inches (38.1 mm).
Valve Seat Angle: 45 deg.
Valve Stem Diameter: 0.3437 inches (8.73 mm).
Valve Lash (cold): Intake 0.015 inches (0.38 mm), Exhaust 0.017 inches
(0.43 mm).
Adjustment is performed with the engine cold.
The fuel system is a direct injection design utilizing a rotary
distributor injection pump.
Injection Pump: An International Harvester/Bosch VE-type rotary
distributor pump, mechanically governed.
This pump is gear-driven from the engine's front timing gear train.
Injection Nozzles: Multi-hole pintle nozzles designed for optimal fuel
atomization in a direct injection combustion chamber.
Injection Pressure: 2000 to 2200 psi (138 to 152 bar).
Fuel Lift Pump: A camshaft-driven, diaphragm-type mechanical transfer
pump.
Fuel Filter: A dual-stage filtration system, often with a primary
sedimentor/water separator and a secondary spin-on paper element filter.
Static Injection Timing: Requires precise setting using engine timing
marks.
The common static timing setting is 18 deg before top dead center.
Dynamic timing procedures with a dial indicator are specified for
accurate final adjustment.
The lubrication system is a full-pressure, full-flow design with a
gear-type pump.
Oil Pump: Gear-type, mounted on the front of the cylinder block and
driven by the crankshaft gear.
Oil Capacity: Approximately 11 quarts (10.4 liters) including filter.
Oil Filter: Full-flow, spin-on type cartridge.
Oil Pressure (operating): 40 to 60 psi at rated speed (2.8 to 4.1 bar).
Minimum acceptable pressure at a hot idle is 10 psi (0.7 bar).
Pressure Relief Valve: Integral to the oil pump housing.
Oil Cooler: An engine oil cooler is standard equipment, cooled by engine
coolant.
The cooling system is a pressurized, forced-circulation system with
thermostatic control.
Water Pump: Centrifugal type, belt-driven from the crankshaft pulley.
Thermostat: Wax-pellet type, begins to open at 180 F (82 C).
Radiator Pressure Cap: 7 psi pressure cap (0.48 bar).
Coolant Capacity: 21 quarts (19.9 liters).
Coolant Recommendation: A 50/50 mixture of ethylene glycol antifreeze
and demineralized water.
Supplemental coolant additives are recommended for heavy-duty service to
protect against cavitation and corrosion.
Electrical System: 12-volt negative ground.
Starting Motor: 12-volt, high-torque gear reduction type, solenoid
actuated.
Charging Alternator: 12-volt, 65 to 90 ampere output, belt-driven with
an internal regulator.
Battery Recommendation: Group 31 or equivalent, with a minimum of 800
cold cranking amps.
Some applications may utilize dual batteries.
Air Intake System: Dual-stage dry type air cleaner.
This system consists of a primary cyclonic pre-cleaner and a secondary
replaceable paper safety element. Intake Manifold: Cast iron. Exhaust
Manifold: Cast iron.
Length (front of damper to rear of flywheel housing): 41 inches (1041
mm).
Width (over valve cover): 27 inches (686 mm).
Height (top of valve cover to base of oil pan): 32 inches (813 mm).
Weight (dry, as described): 1100 lbs (499 kg).
Engine Oil Grade: Use a high-quality diesel engine oil meeting API
service classification CD or superior. SAE 15W-40 is the recommended
viscosity for multi-temperature operation. Oil Change Interval: Under
normal agricultural service, change engine oil and filter every 150
operating hours. For severe service conditions, reduce the interval to
100 hours. Oil Filter Change: Replace the spin-on filter with every oil
change.
Fuel Filter Change: Service the primary sediment bowl daily. Replace the
primary and secondary fuel filter elements every 500 operating hours.
Coolant Change: Drain, flush, and refill the cooling system every 2000
operating hours or 24 months. Maintain proper coolant additive
concentration. Air Filter Service: Empty the cyclonic pre-cleaner daily
during dusty operation. Inspect the primary paper element every 100
hours. Replace the element when a restriction indicator shows red or
every 1000 hours.
Valve Lash Adjustment: Check and adjust valve clearance every 1000
operating hours or annually. Injection Timing Check: Verify static
injection timing every 2000 operating hours or following any disassembly
of the fuel pump drive system. Cylinder Liner Protrusion: During
overhaul, measure and verify wet sleeve protrusion above the block deck.
Specification is 0.002 to 0.005 inches (0.05 to 0.13 mm).
Cylinder Head Bolts: Torque in the specified three-step sequence to a
final value of 120 to 125 lb-ft (163 to 169 Nm). Main Bearing Cap Bolts:
100 to 110 lb-ft (136 to 149 Nm).
Connecting Rod Cap Nuts: 55 to 60 lb-ft (75 to 81 Nm).
Flywheel to Crankshaft Bolts: 95 to 105 lb-ft (129 to 142 Nm).
Injector Nozzle Holder (in head): 60 to 65 lb-ft (81 to 88 Nm).
Rocker Arm Shaft Bracket Bolts: 25 to 30 lb-ft (34 to 41 Nm).
Oil Pan Drain Plug: 30 to 35 lb-ft (41 to 47 Nm).
The International Harvester D312 engine was a primary powerplant for a
series of mid-range agricultural tractors. Its principal applications
include International Harvester tractors such as the 666 and 686. This
engine provided the smooth, dependable power required for these models,
supporting a wide array of farming tasks including heavy tillage,
planting, hay handling, and loader work.
The D312 was integral to these tractor platforms, representing a modern
six-cylinder diesel option during its production period. The engine also
saw use in some stationary industrial applications. Confirmation of the
engine model should always be verified via the engine serial number
plate located on the block.
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