International C263 Specifications
| Engine Model: International Harvester C263 |
| Engine Type: 4-stroke in-line 6-cylinder liquid-cooled gasoline |
| Total Displacement: 263.1 cu.in (4.31 L) |
| Rated Engine Power: 61-74 Hp (48-56 kW) at 2400 rpm |
| Fuel System Type: Updraft carburetor |
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The International C-263 is a 4.3-liter, inline
6-cylinder gasoline engine produced by International Harvester (IH) from
the late 1950s through the late 1960s. Derived from the "Black Diamond"
truck engine series, it became a staple of the IH "06 Series" tractors,
most notably powering the Farmall 560, 660, 656, and early 706. This
engine represents the culmination of IH’s philosophy of building rugged,
durable powerplants for agricultural applications.
The C263 is characterized by its heavy-duty cast iron construction,
replaceable wet cylinder liners in tractor versions, and a relatively
low compression ratio suited for variable fuel quality and sustained
low-speed operation. Its design prioritized torque rise and longevity
over outright horsepower, making it a trusted workhorse on farms across
North America. The engine was also adapted for use in IH combines and
industrial equipment, with minor variations in internal components and
power ratings.
The International C-263 is a naturally aspirated, four-cycle, inline
6-cylinder gasoline engine. The cylinder arrangement is vertical and
in-line, designed for longitudinal mounting within the chassis or engine
frame of agricultural tractors and harvesters. The engine block and
cylinder head are constructed from high-strength cast iron with
extensive ribbing to dampen vibration and provide structural rigidity
under heavy loads.
The valvetrain is an overhead valve (OHV) design with pushrods and
rocker arms, actuated by a camshaft located in the cylinder block. Each
cylinder features two valves - one intake and one exhaust - arranged in
a straight line along the cylinder head. This simple, robust valvetrain
configuration was selected for ease of service and reliability in dusty
agricultural environments.
Displacement is 263.1 cubic inches (4.31 L), achieved through a bore of
3.5625 in (90.5 mm) and a stroke of 4.390 in (111.5 mm). The long-stroke
design produces favorable torque characteristics at low engine speeds,
essential for drawbar and power take-off (PTO) applications. The
compression ratio is 7.5:1, a conservative value allowing the engine to
operate on low-octane gasoline without detonation.
The firing order is 1-5-3-6-2-4, a sequence that balances primary and
secondary forces within the inline six configuration, reducing
crankshaft torsional vibration. Power output varies by application and
governed engine speed. The Farmall 560 produces approximately 60 to 65
PTO horsepower at 1,800 rpm. The Farmall 656 delivers approximately 66
PTO horsepower. The early Farmall 706 generates approximately 73 PTO
horsepower at 2,100 to 2,300 rpm. The Farmall 660 produces up to 80
horsepower at 2,400 rpm. In combine applications, such as the IH 403,
the engine is rated up to 90 gross horsepower at 2,600 rpm.
The cylinder block is a cast iron unit with deep ribbed side walls and a
heavy-duty lower crankcase section. This design provides exceptional
rigidity under torsional loads encountered during plowing, disking, and
other heavy tillage operations. The block features a 4-main-bearing
configuration for the crankshaft, unlike the 7-main-bearing design found
in some competing engines. This simplification reduces manufacturing
complexity while maintaining adequate support for the engine’s intended
operating range.
A defining feature of the tractor version C263 is the use of replaceable
"wet" cylinder sleeves. These sleeves are in direct contact with the
engine coolant, providing superior heat transfer from the combustion
chamber to the cooling system. The sleeves are held in place by the
cylinder head gasket when the head is torqued down. Combine versions of
the C263 are frequently sleeveless, with the cylinders bored directly
into the cast iron block. The crankshaft is forged from high-carbon
steel and features six counterweights. Connecting rods are forged steel
with a precision-finished big end bore.
The cylinder head is a single, cast iron unit spanning all six
cylinders. The combustion chamber is of the wedge type, with valves
angled to promote swirl and efficient flame propagation. Intake and
exhaust valves are positioned on the same side of the cylinder head,
with pushrods passing through openings in the head to actuate the rocker
arms.
Valve diameter is generous for the engine displacement, supporting
adequate volumetric efficiency at governed speeds. The valve train
includes adjustable rocker arms with threaded studs and locking nuts,
allowing precise valve clearance setting. Valve seats are
induction-hardened directly into the cast iron head, a method providing
excellent durability without separate seat inserts. Valve guides are
also integral to the head casting. The exhaust valve stems often receive
a sodium-cooled or Stellite-faced treatment in higher-output versions to
withstand elevated temperatures during continuous heavy load operation.
The fuel system is a gravity-fed or pump-fed updraft carburetion system,
depending on the application and fuel tank location relative to the
engine. The carburetor is either a Zenith or an IHC-built updraft unit
with a single venturi. The updraft design draws air upward through the
carburetor, reducing the risk of fuel spillage during operation on
sloped terrain - a critical consideration for field work.
The carburetor includes a float-type fuel bowl, idle and main metering
circuits, a power enrichment circuit for heavy load conditions, and a
manual or automatic choke. Fuel is delivered from the tank to the
carburetor either by gravity or by a mechanical fuel pump mounted on the
cylinder block and actuated by an eccentric lobe on the camshaft. A
sediment bowl and mesh screen are positioned between the fuel tank and
the carburetor to trap water and debris before they can enter the
metering circuits.
The lubrication system is a full-pressure, gear-type pump design. The
oil pump is mounted inside the oil pan and driven by a shaft from the
distributor drive gear. Oil is drawn through a screened pickup and
passed through the pump before being routed through a full-flow
replaceable oil filter. From the filter, pressurized oil travels to main
galleries machined into the cylinder block.
Oil is delivered to the crankshaft main bearings, connecting rod
bearings, and camshaft bearings through drilled passages. A separate oil
passage directs pressurized oil upward through the cylinder block and
cylinder head to the rocker shaft assembly, where it lubricates the
rocker arms, valve tips, and pushrod sockets. The system includes a
pressure relief valve set to maintain consistent oil pressure across the
engine speed range. Low-ash oil is required to prevent valve and
combustion chamber deposit formation, a known concern with
high-phosphorus and high-zinc additives in older engine designs.
The cooling system is a thermosiphon or pump-circulated liquid cooling
system, with most applications utilizing a belt-driven centrifugal water
pump. Coolant is drawn from the lower radiator tank, circulated through
the cylinder block and cylinder head, and returned to the upper radiator
tank. The use of wet cylinder sleeves in tractor versions allows coolant
to contact the sleeves directly, providing efficient heat transfer from
the combustion zone.
A wax-pellet or bellows-type thermostat, with an opening temperature of
160°F to 180°F (71°C to 82°C), regulates coolant flow to maintain stable
operating temperatures. A fan, mounted on the water pump pulley or
crankshaft pulley, draws air through the radiator core. The system
includes a radiator pressure cap rated for 4 to 7 psi (28 to 48 kPa) to
raise the boiling point of the coolant and prevent cavitation around the
water pump impeller.
Ignition System: The ignition system is a battery-and-coil,
distributor-type design. A 12-volt electrical system is standard on most
C-263 applications, with some early versions utilizing 6-volt systems
later converted. The distributor is mechanical advance with centrifugal
and vacuum advance mechanisms. A cam-actuated breaker point assembly
interrupts the primary circuit to generate high secondary voltage in the
ignition coil. Spark is distributed to each cylinder in the 1-5-3-6-2-4
firing order through a rotor and distributor cap.
Intake System: The intake manifold is a cast iron unit with a
single-plane design feeding all six cylinders. The manifold features a
central carburetor mounting flange and a heated crossover passage from
the exhaust manifold. This exhaust heat crossover warms the intake
mixture during cold start and warm-up, improving fuel vaporization. A
manual or thermostatically controlled heat riser valve directs exhaust
flow through the crossover passage when the engine is cold.
Governor System: A mechanical centrifugal governor is installed on all
tractor and combine applications. The governor is driven by a gear from
the camshaft and adjusts the carburetor throttle plate position to
maintain a preset engine speed regardless of load changes. Governor
response is calibrated for agricultural duty, providing droop
characteristics that allow stable operation of PTO-driven implements.
Length, measured from the front pulley to the flywheel housing mounting
face, is 36.0 in (914 mm). Width, measured across the cylinder head and
intake manifold, is 24.0 in (610 mm). Height from the bottom of the oil
pan to the top of the valve cover is 32.0 in (813 mm). The dry weight of
the complete engine assembly, including the flywheel, intake and exhaust
manifolds, carburetor, starter, and distributor, is 700 lb (318 kg).
Oil Capacity: With filter change, the crankcase capacity is 7.0 US qt
(6.6 L). Without filter change, capacity is 6.0 US qt (5.7 L). Spark
Plugs: The recommended spark plug is Champion H10 or equivalent. The
spark plug gap is 0.025 in (0.64 mm). Breaker Point Gap: The distributor
breaker point gap is 0.020 in (0.51 mm). Dwell angle should be set to 32
to 38 degrees.
Ignition Timing: Initial timing is set to 6 degrees before top dead
center (BTDC) at idle speed. Centrifugal advance advances timing to
approximately 28 degrees BTDC at rated governed speed. Valve Clearance
(Hot): Adjust with the engine at operating temperature. Intake valve
clearance is 0.014 in (0.36 mm). Exhaust valve clearance is 0.016 in
(0.41 mm).
Engine Coolant: The cooling system capacity, including the radiator, is
approximately 14.0 US qt (13.2 L). A 50/50 mixture of ethylene glycol
antifreeze and water is recommended. Oil Change Interval: Under normal
agricultural service, the engine oil and filter should be changed every
100 operating hours or every six months, whichever comes first. Air
Cleaner: The engine uses an oil-bath air cleaner. The oil cup should be
cleaned and refilled with fresh engine oil every 50 operating hours in
dusty conditions.
Cylinder Head Bolts: 90 lb-ft (122 Nm).
Connecting Rod Bolts (Place Bolt): 50 lb-ft (68 Nm).
Connecting Rod Bolts (Pitch Bolt): 45 lb-ft (61 Nm).
Main Bearing Cap Bolts: 80 lb-ft (108 Nm).
Rocker Arm Shaft Bolts: 90 lb-ft (122 Nm).
Flywheel Housing to Block Bolts: 40 lb-ft (54 Nm).
Flywheel to Crankshaft Bolts: 55 lb-ft (75 Nm).
Intake Manifold Nuts: 25 lb-ft (34 Nm).
Exhaust Manifold Nuts: 25 lb-ft (34 Nm).
Spark Plugs: 25 lb-ft (34 Nm).
Oil Pan Bolts: 15 lb-ft (20 Nm).
Valve Cover Bolts: 5 lb-ft (7 Nm).
Carburetor Mounting Nuts: 20 lb-ft (27 Nm).
Water Pump Mounting Bolts: 25 lb-ft (34 Nm).
Crankshaft Pulley Bolt: 130 lb-ft (176 Nm).
The International C263 engine was utilized across a broad range of
International Harvester agricultural and industrial equipment during its
production life.
Tractor Applications:
Farmall 560 (late production)
Farmall 660
Farmall 656 (gasoline version)
International 656 (utility version)
Farmall 706 (early production, before the D-282 diesel and later C-291
gasoline)
International 706 (early utility version)
International 2606 industrial tractor
Combine Applications:
IH 403 Combine
IH 503 Combine
Other Applications:
IH 351 industrial engine (stationary power unit)
Certain IH truck models during the transition between the Black Diamond
and C-series engine families
The C-263 was phased out of tractor production in the late 1960s,
replaced by the larger C-291 and C-301 engines in the "56 Series" and
later models. However, its reputation for durability and ease of
maintenance has made it a sought-after engine for restoration of IH "06
Series" tractors and combines.
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