International C301 Specifications
| Engine Model: International Harvester C301 |
| Engine Type: 4-stroke in-line 6-cylinder liquid-cooled gasoline |
| Total Displacement: 301.1 cu.in (4.93 L) |
| Rated Engine Power: 110-115 Hp (81-85 kW) at 2400 rpm |
| Fuel System Type: Updraft carburetor |
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The International C301 is a 4.9-liter, inline
6-cylinder gasoline and LP-gas engine produced by International
Harvester (IH) during the 1960s. As the largest displacement gasoline
engine in the "06" and "26" series tractor families, the C301 was
engineered for sustained heavy-duty agricultural service. It most
famously powered the Farmall 806 and 826 row-crop tractors, alongside
various high-capacity combines and stationary industrial power units.
Unlike smaller IH gasoline engines of the era, the C301 shares its
fundamental block architecture with the D-361 diesel, resulting in an
unusually robust cast-iron structure. The engine emphasizes torque rise
at lower engine speeds, with a broad power band from 1,500 rpm to the
rated 2,400 rpm. Available in both gasoline and LP-gas configurations,
the C301 offered farmers a reliable, high-torque solution for heavy
tillage operations before diesel engines became dominant in this power
class.
The International C301 is a naturally aspirated, four-stroke, inline
six-cylinder engine operating on the Otto cycle. The engine block is
configured for a transverse or inline mounting orientation within the
tractor chassis. Displacement measures 301.1 cubic inches, equivalent to
4.93 liters. The bore is 3.8125 inches (96.8 mm) with a stroke of 4.390
inches (111.5 mm), producing an undersquare design that favors low-end
torque production. Compression ratio varies by fuel type: the gasoline
version operates at 7.5:1, while the LP-gas version maintains a higher
8.5:1 ratio to exploit the higher octane rating of propane.
The firing order is 1-5-3-6-2-4, standard for inline six-cylinder
engines to maintain primary and secondary balance. Valvetrain
configuration is overhead valve (OHV) with pushrods and rocker arms
actuated by a camshaft located in the cylinder block. Gross engine
horsepower is rated between 110 and 115 hp at 2,400 rpm. Power take-off
(PTO) horsepower measures 92-95 hp, while drawbar horsepower ranges from
80-84 hp. Maximum torque is achieved between 1,500 and 1,600 rpm,
producing 250-260 lb-ft.
The cylinder block is a single-piece cast-iron construction, notable for
its substantial wall thickness and weight. This block architecture is
shared with the D-361 diesel engine, providing exceptional rigidity for
a gasoline engine of this era. The C301 utilizes replaceable wet
cylinder sleeves pressed into the block. These sleeves are open at the
bottom, with coolant circulating directly around their external surfaces
to improve heat transfer from the cylinder bores.
The wet sleeve design allows for in-frame overhaul without removing the
entire engine from the tractor chassis. The water jacket surrounds each
sleeve completely, with coolant flow directed through multiple ports in
the block deck. The block incorporates seven main bearing webs,
supporting a forged steel crankshaft. A gear train at the front of the
block drives the camshaft, distributor, oil pump, and mechanical
governor. The crankcase is sealed by a stamped steel oil pan with a
gasketed rail surface.
The cylinder head is a single cast-iron unit spanning all six cylinders.
It attaches to the block using separate studs and nuts rather than
bolts, providing more consistent clamping force across the head gasket.
The combustion chambers are a bathtub design, sized to match the bore
diameter and promote swirl for improved air-fuel mixing. Valves are
arranged in a single row, with intake and exhaust valves angled toward
the combustion chamber. Valve diameters are sized for low-speed
volumetric efficiency rather than high-rpm flow.
The intake valves are larger than the exhaust valves to maximize charge
density during the intake stroke. Each cylinder has one intake and one
exhaust valve, both equipped with rotor-type valve rotators that spin
the valve slightly with each opening event. This rotation prevents
localized hot spots and reduces carbon buildup on the valve faces. Valve
stem seals are used on the intake valves to control oil consumption. The
valve train is actuated by a camshaft located in the cylinder block,
which pushes hollow pushrods that transfer motion to adjustable rocker
arms.
The fuel system varies between gasoline and LP-gas configurations. On
gasoline models, the system comprises a mechanical fuel pump mounted to
the cylinder block, drawing fuel from a tractor-mounted tank. Fuel
passes through a sediment bowl with a replaceable filter screen before
entering an updraft carburetor, Zenith or equivalent. The updraft design
draws air upward through the carburetor, requiring a long intake
manifold with individual runners to each cylinder. On LP-gas models, the
system substitutes a vaporizer-regulator that converts liquid propane to
vapor before metering it into a specialized mixer mounted in place of
the carburetor.
The LP-gas configuration also includes a larger intake manifold to
accommodate the higher volumetric requirements of gaseous fuel. Both
fuel systems integrate with a mechanical flyweight governor, which
adjusts the throttle plate position to maintain a constant engine speed
under varying loads. The governor connects directly to the carburetor
throttle shaft via a series of linkages.
The lubrication system is a full-pressure design using a gear-type oil
pump driven from the camshaft gear. The pump draws oil from a sump
through a screened pickup tube, then forces it through a full-flow
canister oil filter mounted externally on the engine block. After
filtration, oil circulates through drilled passages in the block to the
seven main bearings, camshaft bearings, and connecting rod bearings. A
separate passage routes oil upward through the cylinder head to the
rocker shaft assembly.
The rocker arms receive oil through hollow shafts, with excess oil
draining back to the crankcase through pushrod passages and return holes
in the head. Total oil capacity, including the filter, ranges from 8.0
to 9.0 quarts (7.6 to 8.5 liters). Operating oil pressure at rated speed
(2,400 rpm) measures between 35 and 55 psi. A pressure relief valve
located near the oil pump protects the system from over-pressurization
during cold starts.
The cooling system is a pressurized, thermosiphon-assisted design driven
by a belt-driven centrifugal water pump mounted at the front of the
engine. Coolant circulates from the lower radiator tank through the
water pump, then enters the cylinder block at the front and flows
rearward through the water jacket surrounding the wet cylinder sleeves.
Coolant rises through ports in the head gasket into the cylinder head,
where it flows around the exhaust valve seats and combustion chambers
before exiting through a thermostat housing at the front of the head.
A wax-pellet thermostat rated at 180°F (82°C) controls coolant flow to
the radiator, bypassing the radiator until operating temperature is
reached. Total coolant capacity ranges from 23.0 to 25.0 quarts (21.7 to
23.6 liters). The system uses a cross-flow or down-flow radiator
depending on the chassis application, with a fan mounted on the water
pump pulley drawing air through the radiator core. A pressure-type
radiator cap maintains system pressure at approximately 7-10 psi to
raise the boiling point of the coolant.
Ignition System: A 12-volt, negative-ground electrical system supplies
power to a battery ignition coil and a distributor. The distributor
houses breaker points (0.020-inch gap) and a centrifugal advance
mechanism. Ignition timing at idle is set to 6° before top dead center
(BTDC), advancing to 28° BTDC at full engine speed. A vacuum advance
unit is not present on most agricultural applications, as load-based
timing changes are handled by the governor.
Governor System: A mechanical flyweight governor mounts to the front of
the engine, driven directly by the camshaft gear. The governor senses
engine speed via centrifugal force acting on weighted flyweights. The
throttle lever position from the operator sets a spring tension against
the governor. As engine load increases and speed drops, the flyweights
move inward, opening the carburetor throttle plate wider to restore
speed. This system maintains a fixed engine rpm regardless of load
variation up to the engine's torque limit.
Exhaust System: A cast-iron exhaust manifold with a single outlet routes
exhaust gases from all six cylinders to a vertical muffler and stack.
The manifold design incorporates a heat riser valve that directs exhaust
flow against the intake manifold during warm-up to vaporize fuel more
effectively.
Starting System: A 12-volt electric starter motor engages a ring gear on
the flywheel. On LP-gas models, a priming circuit may be present to
introduce liquid propane into the intake manifold for cold starting
before the vaporizer reaches operating temperature.
Overall length, measured from the front timing gear cover to the
flywheel housing mating surface, is 38 inches (965 mm). Width, measured
across the widest point at the cylinder head and intake manifold, is 24
inches (610 mm). Height from the bottom of the oil pan to the top of the
rocker arm cover is 34 inches (864 mm).
The dry weight of the complete engine, inclusive of the intake manifold,
exhaust manifold, carburetor, starter, generator, and flywheel, is 950
lb (431 kg). The long block assembly (cylinder block, crankshaft,
connecting rods, pistons, and cylinder head) weighs 750 lb (340 kg). The
crankshaft alone contributes 120 lb (54 kg) due to its forged steel
construction and seven main bearing journals.
Engine oil and filter changes are recommended every 100 hours of
operation under normal field conditions. The crankcase capacity with a
filter change is 8.5 quarts (8.0 liters). Recommended oil viscosity is
SAE 30 for temperatures above freezing, or SAE 10W-30 for year-round use
in moderate climates. Spark plugs must be replaced or cleaned every 200
hours. The spark plug gap is 0.025 inches (0.64 mm). Breaker point gap
must be checked every 100 hours, set to 0.020 inches (0.51 mm).
Replacement points, condenser, and rotor are required every 300-400
hours. Valve lash adjustments are performed with the engine at operating
temperature. Intake and exhaust valves share the same clearance: 0.014
inches (0.36 mm). The cooling system requires drainage and refill every
two years or 1,000 hours using a mixture of ethylene glycol antifreeze
and soft water at a 50:50 ratio.
The mechanical fuel pump diaphragm should be inspected annually for
cracking or fuel leakage. The air cleaner, an oil-bath type on most
applications, requires cleaning of the oil cup and replacement of the
oil charge every 100 hours under dusty conditions. The wet cylinder
liners are serviceable; a major overhaul includes replacing the six
sleeves, pistons, and rings without removing the block from the chassis.
Cylinder Head Nuts: 95-105 lb-ft (129-142 Nm).
Connecting Rod Bolts: 50-55 lb-ft (68-75 Nm).
Main Bearing Cap Bolts: 100-110 lb-ft (136-149 Nm).
Flywheel Bolts (to Crankshaft Flange): 80-90 lb-ft (108-122 Nm).
Rocker Arm Shaft Bracket Bolts: 25-30 lb-ft (34-41 Nm).
Intake Manifold Nuts: 20-25 lb-ft (27-34 Nm).
Exhaust Manifold Nuts: 20-25 lb-ft (27-34 Nm).
Oil Pan Bolts: 12-15 lb-ft (16-20 Nm).
Timing Gear Cover Bolts: 15-18 lb-ft (20-24 Nm).
Water Pump Mounting Bolts: 25-30 lb-ft (34-41 Nm).
Flywheel Housing to Block Bolts: 40-50 lb-ft (54-68 Nm).
Valve Cover Bolts: 5-7 lb-ft (7-9 Nm).
Carburetor Mounting Nuts (Updraft): 15-20 lb-ft (20-27 Nm).
Spark Plugs: 20-25 lb-ft (27-34 Nm).
The International C301 engine served as the top gasoline power option
across the International Harvester agricultural and industrial lineup
during the 1960s.
Farmall 806 Row-Crop Tractor (1963-1967): The most common application.
The C301 supplied 92-95 PTO hp in gasoline form, with an LP-gas variant
available for specialized markets.
Farmall 826 Row-Crop Tractor (1968-1971): Successor to the 806. The C301
continued as the gasoline option until the model’s discontinuation.
International 806 Standard/Utility Tractor: Same engine specification as
the Farmall 806, configured for wheeled industrial and large-acreage
applications.
International 826 Standard/Utility Tractor: The C301 appeared in both
gasoline and LP-gas variants.
International 151 Combine: A large-capacity combine requiring sustained
high power output.
International 181 Combine: The C301 served as an optional gasoline
engine in early production of this model.
International U-301 Power Unit: A stationary industrial version of the
C301, equipped with a radiator, governor, and skid mounting for use in
pumps, generators, and feed grinders. This variant continued in
production into the early 1970s.
International 4300 Series Industrial Tractor: Some early units of this
heavy-duty loader tractor used the C301 before diesel adoption became
universal.
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