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International C301 Engine

The International Harvester C301 is a heavy-duty, naturally aspirated, inline 6-cylinder internal combustion engine designed for agricultural, industrial, and stationary power applications. It belongs to IH's long-running family of robust, carbureted six-cylinder powerplants and was commonly utilized in high-horsepower platforms such as the Farmall 806, 826, and 856 tractors, as well as the 715 combine. Engineered for sustained high-torque outputs under continuous load, the engine features a parent-bore design (sleeveless cylinder block) to maximize rigid structural integrity.

Valve Configuration: Overhead valve (OHV) design utilizing two valves per cylinder actuated by a gear-driven camshaft, pushrods, and rocker arms. Bore and Stroke: The cylinder bore is 3.8125 inches (97 mm) and the piston stroke is 4.39 inches (112 mm). Total engine displacement measures 301 cubic inches (4.9 liters). Cooling System: Liquid-cooled setup utilizing a high-capacity centrifugal water pump, a bypass-type thermostat for rapid warm-up cycles, and a pressurized radiator. Force-directed coolant passages are cast into the block and cylinder head to uniformize cooling around the exhaust valve seats and combustion chambers.

Fuel System: Available in both Gasoline and Liquefied Petroleum (LP) gas variants. The fuel system utilizes a heavy-duty, updraft single-throat carburetor paired with a mechanical, velocity-sensing flywheel governor to maintain stable RPM across fluctuating load profiles. High-altitude or high-compression implementations are configured with specialized domed pistons to optimize combustion efficiency when specified. Lubrication System: Full pressure-feed lubrication system supplied by a positive displacement, gear-type oil pump driven internally from the camshaft. Engine oil is circulated through a full-flow oil filtration block incorporating a bypass valve to maintain pressure integrity during cold starts.

General Technical Data

Engine Specifications

Engine Model ............... International Harvester C301
Engine Type ............... 4-cycle inline 6-cylinder carburetor spark-ignition liquid-cooled gasoline
Number of Cylinders ............... 6
Cylinder Arrangement ............... In-line
Engine Bore, in (mm) ............... 3.8125 (96.84)
Engine Stroke, in (mm) ............... 4.390 (111.51)
Displacement, cu.in (L) ............... 301.2 (4.94)
Rated Engine Power, hp (kW) ............... 93-110 (69-82)
Rated Engine Speed, rpm ............... 2400
Peak Torque ............... 245-265 lb-ft (332-359 Nm) at 1200-1500 rpm
Idle Speed ............... 700-750 rpm
High Idle Speed ............... 2625-2650 rpm
Compression Ratio Gas ............... 7.7:1
Compression Ratio LPG ............... 8.8:1
Firing Order ............... 1-5-3-6-2-4
Cylinder Block Type ............... Cast iron parent bore sleeveless
Cylinder Head Type ............... Cast iron overhead valve 12-valve
Lubrication System ............... Full-pressure gear-driven
Oil Pump Type ............... Gear-driven inner and outer rotors
Oil Filter Type ............... Full-flow spin-on cartridge element
Cooling System ............... Liquid-cooled centrifugal force forced-circulation
Water Pump Type ............... Belt-driven centrifugal impeller
Air Cleaner Type ............... Heavy-duty oil bath or dry dual-element
Ignition System ............... Battery-powered distributor breaker points or electronic
Spark Plug Type ............... Champion D16 or equivalent
Spark Plug Gap, in (mm) ............... 0.023-0.027 (0.58-0.69)
Distributor Point Gap, in (mm) ............... 0.020 (0.51)
Starting System ............... Electric starter motor solenoid-engaged
Electrical System, V ............... 12
Ground Polarity ............... Negative ground

Fuel System

Fuel System Type, Gas ............... Updraft single-barrel carburetor
Fuel System Type, LPG ............... Liquefied petroleum gas liquid/vapor withdrawal converter carb
Carburetor Manufacturer ............... Zenith or Marvel-Schebler
Carburetor Throat Diameter, in (mm) ............... 1.25 (31.75)
Main Jet Size, Gas ............... 0.057-0.061 in (1.45-1.55 mm)
Idle Jet Size, Gas ............... 0.023-0.027 in (0.58-0.69 mm)
Choke Bore Diameter, in (mm) ............... 1.625 (41.28)
Fuel Delivery Pressure, psi (kPa) ............... 3.5-5.0 (24.1-34.5)
LPG Converter Regulator Pressure, psi (kPa) ............... 4.5-5.5 (31.0-37.9)
LPG Carburetor Model ............... Century or Ensign single-barrel
Fuel Strainer Type ............... Sediment bowl screen-mesh assembly
Air-to-Fuel Ratio,Gas ............... 14.7:1
Air-to-Fuel Ratio,LPG ............... 15.5:1
Governor Type ............... Mechanical centrifugal flyweight variable-speed

Dimensions and Weight

Overall Length, in (mm) ............... 41.3 (1050)
Overall Width, in (mm) ............... 22.8 (580)
Overall Height, in (mm) ............... 36.6 (930)
Dry Weight, lbs (kg) ............... 745-780 (338-354)
Wet Weight, lbs (kg) ............... 795-835 (361-379)

Maintenance Data

Service Information

Compression Pressure, Standard, psi (kPa) ............... 145-165 (1000.0-1137.6)
Maximum Compression Variance, psi (kPa) ............... 10 (68.9)
Oil Pressure at Rated Speed, psi (kPa) ............... 45-55 (310.2-379.2)
Oil Pressure at Idle Speed, psi (kPa) ............... 15 (103.4)
Thermostat Opening Temperature, F (C) ............... 170-180 (76.6-82.2)
Thermostat Fully Open Temperature, F (C) ............... 202 (94.4)
Radiator Cap Pressure Rating, psi (kPa) ............... 7.0 (48.3)
Ignition Timing Initial Base, Deg BTDC ............... 4
Ignition Timing Maximum Advance, Deg BTDC ............... 22
Fan Belt Tension Deflection, in (mm) ............... 0.50-0.75 (12.7-19.1)
Intake Valve Clearance, Cold, in (mm) ............... 0.014 (0.36)
Exhaust Valve Clearance, Cold, in (mm) ............... 0.018 (0.46)

Engine Oil and Coolant

Engine Oil Type .................. SAE 30, SAE 10W-30, or 15W-40
API Service Classifications ......................... CC or CD
Engine Oil Capacity with Filter, qt (L) ............... 8.0 (7.57)
Engine Oil Capacity Crankcase Only, qt (L) ............... 7.0 (6.62)
Air Cleaner Oil Bath Capacity, qt (L) ............... 1.25 (1.18)
Cooling System Capacity, qt (L) ............... 24.0 (22.7)

Service Intervals

Change oil and filter ............... Every 100 hours
Inspect air cleaner ............... Every 50 hours
Service air cleaner ............... Every 500 hours
Valve clearance adjustment ............... Every 500 hours
Fuel system inspection ............... Every 1000 hours
Change coolant ............... Every 1000 hours
Spark plug replacement ............... Every 500 hours
Check ignition system ............... Every 500 hours

Service Specifications

Cylinder Bore Diameter, in (mm) ............... 3.8120-3.8135 (96.824-96.862)
Cylinder Bore Maximum Out-of-Round, in (mm) ............... 0.003 (0.076)
Cylinder Bore Maximum Rebore Limit, in (mm) ............... 0.060 (1.524)
Crankshaft Main Journal Diameter, in (mm) ............... 2.7485-2.7495 (69.811-69.837)
Crankshaft Main Bearing Bore in Block, in (mm) ............... 2.9420-2.9430 (74.726-74.752)
Crankshaft Main Bearing Clearance, in (mm) ............... 0.0018-0.0036 (0.0457-0.0914)
Crankshaft Main Journal Maximum Out-of-Round, in (mm) ............... 0.0005 (0.0127)
Crankshaft Main Journal Maximum Taper, in (mm) ............... 0.0005 (0.0127)
Crankshaft End Play, in (mm) ............... 0.0040-0.0080 (0.1016-0.2032)
Connecting Rod Journal Diameter, in (mm) ............... 2.2485-2.2495 (57.111-57.137)
Connecting Rod Bearing Big End Bore, in (mm) ............... 2.4235-2.4245 (61.556-61.582)
Connecting Rod Bearing Clearance, in (mm) ............... 0.0015-0.0032 (0.0381-0.0812)
Connecting Rod Side Clearance End Play, in (mm) ............... 0.0070-0.0130 (0.1778-0.3302)
Piston Skirt Diameter, in (mm) ............... 3.8085-3.8100 (96.735-96.774)
Piston-to-Cylinder Wall Clearance, in (mm) ............... 0.0030-0.0045 (0.076-0.114)
Piston Pin Bore Diameter in Piston, in (mm) ............... 1.1252-1.1255 (28.580-28.587)
Piston Pin Outside Diameter, in (mm) ............... 1.1249-1.1251 (28.572-28.577)
Piston Pin-to-Piston Bore Clearance, in (mm) ............... 0.0001-0.0004 (0.0025-0.0101)
Piston Pin-to-Con Rod Bushing Clearance, in (mm) ............... 0.0005-0.0009 (0.0127-0.0228)
Top Ring Groove Width, in (mm) ............... 0.0955-0.0965 (2.425-2.451)
Second Ring Groove Width, in (mm) ............... 0.0955-0.0965 (2.425-2.451)
Oil Ring Groove Width, in (mm) ............... 0.1885-0.1895 (4.787-4.813)
Top Ring Side Clearance, in (mm) ............... 0.0020-0.0040 (0.051-0.102)
Second Ring Side Clearance, in (mm) ............... 0.0015-0.0035 (0.038-0.089)
Oil Control Ring Side Clearance, in (mm) ............... 0.0015-0.0035 (0.038-0.089)
Top Ring End Gap, in (mm) ............... 0.013-0.023 (0.330-0.584)
Second Ring End Gap, in (mm) ............... 0.013-0.023 (0.330-0.584)
Oil Control Ring End Gap, in (mm) ............... 0.015-0.025 (0.381-0.635)
Cylinder Head Flatness Maximum, in (mm) ............... 0.0030 (0.0762)
Cylinder Block Deck Flatness Maximum, in (mm) ............... 0.0040 (0.1016)
Intake Valve Stem Diameter, in (mm) ............... 0.3725-0.3735 (9.461-9.486)
Exhaust Valve Stem Diameter, in (mm) ............... 0.3710-0.3720 (9.423-9.448)
Valve Guide Inside Diameter, in (mm) ............... 0.3755-0.3765 (9.537-9.563)
Intake Valve Stem-to-Guide Clearance, in (mm) ............... 0.0020-0.0040 (0.0508-0.1016)
Exhaust Valve Stem-to-Guide Clearance, in (mm) ............... 0.0035-0.0055 (0.0889-0.1397)
Valve Guide Inside Diameter, Limit Wear, in (mm) ............... 0.3800 (9.652)
Intake Valve Seat Angle, Deg ............... 45
Exhaust Valve Seat Angle, Deg ............... 45
Intake Valve Face Angle, Deg ............... 45
Exhaust Valve Face Angle, Deg ............... 45
Valve Spring Free Length, in (mm) ............... 2.310 (58.674)
Camshaft Journal Diameter (Number 1), in (mm) ............... 2.1235-2.1245 (53.937-53.962)
Camshaft Journal Diameter (Number 2), in (mm) ............... 2.0610-2.0620 (52.349-52.374)
Camshaft Journal Diameter (Number 3), in (mm) ............... 1.9985-1.9995 (50.761-50.787)
Camshaft Journal Diameter (Number 4), in (mm) ............... 1.9360-1.9370 (49.174-49.199)
Camshaft Bearing Clearance, in (mm) ............... 0.0015-0.0035 (0.0381-0.0889)
Camshaft End Play, in (mm) ............... 0.0030-0.0070 (0.0762-0.1778)
Cam Lobe Lift, Intake, in (mm) ............... 0.285 (7.239)
Cam Lobe Lift, Exhaust, in (mm) ............... 0.285 (7.239)
Rocker Arm Shaft Outside Diameter, in (mm) ............... 0.9985-0.9995 (25.361-25.387)
Rocker Arm Bushing Inside Diameter, in (mm) ............... 1.0005-1.0015 (25.412-25.438)
Rocker Arm-to-Shaft Running Clearance, in (mm) ............... 0.0010-0.0030 (0.0254-0.0762)
Tappet Lifter Body Outside Diameter, in (mm) ............... 0.9975-0.9980 (25.336-25.349)
Tappet Lifter Bore Inside Diameter, in (mm) ............... 0.9990-1.0000 (25.374-25.400)
Tappet Lifter Running Clearance, in (mm) ............... 0.0010-0.0025 (0.0254-0.0635)
Timing Gear Backlash Crankshaft-to-Camshaft, in (mm) ............... 0.0030-0.0070 (0.0762-0.1778)
Timing Gear Backlash Camshaft-to-Governor, in (mm) ............... 0.0020-0.0060 (0.0508-0.1524)

Tightening Torques

Cylinder Head Bolts (Stage 1), lb-ft (Nm) ............... 45 (61.0)
Cylinder Head Bolts (Stage 2), lb-ft (Nm) ............... 85 (115.2)
Cylinder Head Bolts (Stage 3), lb-ft (Nm) ............... 115 (155.9)
Connecting Rod Cap Bolts, lb-ft (Nm) ............... 55-60 (74.5-81.3)
Main Bearing Cap Bolts, lb-ft (Nm) ............... 110-120 (149.1-162.7)
Flywheel to Crankshaft Bolts, lb-ft (Nm) ............... 80-85 (108.4-115.2)
Flywheel Housing to Cylinder Block Bolts, lb-ft (Nm) ............... 40-45 (54.2-61.0)
Crankshaft Front Pulley Damper Bolt, lb-ft (Nm) ............... 130-140 (176.2-189.8)
Camshaft Thrust Plate Retaining Bolts, lb-ft (Nm) ............... 17-22 (23.0-29.8)
Camshaft Timing Gear Center Nut, lb-ft (Nm) ............... 90-100 (122.0-135.5)
Rocker Arm Shaft Support Bracket Bolts, lb-ft (Nm) ............... 25-30 (33.9-40.6)
Valve Rocker Arm Cover Screws, lb-ft (Nm) ............... 7-10 (9.5-13.5)
Oil Pan Oil Sump Drain Plug, lb-ft (Nm) ............... 45-50 (61.0-67.8)
Oil Pan Retaining Perimeter Bolts, lb-ft (Nm) ............... 12-15 (16.2-20.3)
Intake Manifold to Cylinder Head Nuts, lb-ft (Nm) ............... 25-30 (33.9-40.6)
Exhaust Manifold to Cylinder Head Nuts, lb-ft (Nm) ............... 25-30 (33.9-40.6)
Oil Pump Assembly to Block Retaining Bolts, lb-ft (Nm) ............... 30-35 (40.6-47.4)
Oil Pump Cover Plate Retaining Bolts, lb-ft (Nm) ............... 12-15 (16.2-20.3)
Water Pump Assembly to Block Bolts, lb-ft (Nm) ............... 25-30 (33.9-40.6)
Water Pump Fan Pulley Hub Nut, lb-ft (Nm) ............... 40-50 (54.2-67.8)
Thermostat Housing Cover Retaining Bolts, lb-ft (Nm) ............... 17-22 (23.0-29.8)
Distributor Hold-down Clamp Screw, lb-ft (Nm) ............... 12-15 (16.2-20.3)
Spark Plugs Threaded into Head, lb-ft (Nm) ............... 25-30 (33.9-40.6)
Governor Housing Assembly Mounting Bolts, lb-ft (Nm) ............... 17-22 (23.0-29.8)
Front Crankcase Timing Gear Cover Bolts, lb-ft (Nm) ............... 15-18 (20.3-24.4)
Starter Motor Flange Mounting Bolts, lb-ft (Nm) ............... 40-45 (54.2-61.0)
Alternator Pivot Support Long Bolt, lb-ft (Nm) ............... 30-35 (40.6-47.4)
Alternator Adjusting Strap Link Bolt, lb-ft (Nm) ............... 15-18 (20.3-24.4)
Oil Filter Header Base to Block Bolts, lb-ft (Nm) ............... 25-30 (33.9-40.6)
Oil Pressure Relief Valve Body Plug, lb-ft (Nm) ............... 35-40 (47.4-54.2)
Engine Front Support Mounting Bolts, lb-ft (Nm) ............... 75-85 (101.6-115.2)
Engine Rear Support Mounting Bolts, lb-ft (Nm) ............... 75-85 (101.6-115.2)
Carburetor Base Flange Mounting Nuts, lb-ft (Nm) ............... 15-18 (20.3-24.4)
Fuel Pump Block Mount Screws, lb-ft (Nm) ............... 12-15 (16.2-20.3)
Exhaust Pipe Flange to Manifold Stud Nuts, lb-ft (Nm) ............... 30-35 (40.6-47.4)
Air Cleaner Intake Duct Clamp Screws, lb-ft (Nm) ............... 4-6 (5.4-8.1)
Flywheel Inspection Cover Screws, lb-ft (Nm) ............... 6-9 (8.1-12.2)
Clutch Pressure Plate to Flywheel Bolts, lb-ft (Nm) ............... 25-30 (33.9-40.6)
Fan Blade Assembly to Water Pump Hub Bolts, lb-ft (Nm) ............... 15-18 (20.3-24.4)

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