________________________________________________________________________________

International C263 Engine

The International Harvester C263 is a heavy-duty, inline 6-cylinder spark-ignition engine widely deployed across International Harvester agricultural tractors, industrial machinery, and combines (such as the Farmall 560, 656, 706, and the 403 combine). Derived from the long-running IH inline-six platform, the engine utilizes a robust cast-iron block design. Depending on the targeted application, the block configuration varies between dry-sleeved variants (typically implemented in farm tractors to facilitate straightforward field rebuilding) and sleeveless parent-bore variants (commonly utilized in combine or industrial applications). Known for its excellent torque response at variable load ranges, the engine is valued for its mechanical durability but notes a high fuel consumption rate under full load demands.

The assembly incorporates an Overhead Valve (OHV) arrangement driven by a single gear-driven camshaft nested inside the engine block. There are two valves per cylinder (one intake, one exhaust), oriented vertically within the cylinder head. Mechanical solid lifters actuate pushrods and rocker arms to control valve operation. Bore: 3.5625 inches (90.49 mm). Stroke: 4.3906 inches (111.52 mm). Total Displacement: 263.3 cubic inches (4.3 Liters).

The fuel system is designed to handle gasoline or alternative Liquefied Petroleum Gas (LPG) configurations depending on factory spec. Gasoline Setup: Gravity or mechanical fuel-pump-driven delivery from the primary tank feeds into a single-barrel, side-draft or up-draft carburetor regulated by a mechanical flyweight governor to maintain matching throttle response under load changes. LPG Setup: Liquefied fuel exits the pressurized tank under vapor pressure, passes through a high-pressure filter, flows through a multi-stage converter/regulator unit to convert the liquid into a low-pressure gas vapor, and mixes with air inside a dedicated LPG carburetor gas-mixer assembly. Air intake across both variants is drawn through a dual-stage dry air cleaner assembly.

Engine lubrication is managed via a full-pressure lubrication system powered by a positive-displacement oil pump driven by the camshaft gear assembly. Oil is picked up from the stamped steel oil pan sump through a screened intake floating assembly and pushed through a full-flow oil filter element before entering the main oil gallery. Pressurized oil channels feed directly to the seven main crankshaft bearings, connecting rod journals, and camshaft bearings. An isolated secondary external or internal oil line routes oil upward to the rocker arm shaft assembly to lubricate the valve train components.

The thermal regulation setup consists of a forced-circulation liquid-cooled system. Coolant movement is maintained by a belt-driven centrifugal water pump mounted to the front of the block. A bypass-type single thermostat controls minimum operating temperatures, routing fluid directly back to the pump during warm-up and diverting flow to the heavy-duty radiator core once normal operating thresholds are reached.

General Technical Data

Engine Specifications

Engine Model ............... International Harvester C263
Engine Type ............... 4-cycle inline 6-cylinder overhead valve liquid-cooled gasoline/LPG
Number of Cylinders ............... 6
Cylinder Arrangement ............... In-line
Engine Bore, in (mm) ............... 3.5625 (90.487)
Engine Stroke, in (mm) ............... 4.3906 (111.521)
Displacement, cu.in (L) ............... 263.0 (4.31)
Rated Engine Power, hp (kW) ............... 65-89 (48.5-66.4)
Rated Engine Speed, rpm ............... 2000-2700
High Idle Speed, rpm ............... 2300-2700
Low Idle Speed, rpm ............... 600-650
Maximum Torque, lb-ft (Nm) ............... 215.0 (291.5)
Torque Speed, rpm ............... 1600
Compression Ratio ............... 7.5:1-7.8:1
Firing Order ............... 1-5-3-6-2-4
Direction of Rotation ............... Clockwise facing front pulley assembly
Crankshaft Counterweights ............... Fully balanced integral weights
Piston Material ............... Aluminum alloy dome head autothermic type
Piston Pin Type ............... Full floating design held by circlips
Connecting Rod Material ............... Drop forged I-beam alloy steel construction
Cylinder Liners Type ............... Centrifugally cast dry replaceable sleeves
Manifold Configuration ............... Combination intake and exhaust unit
Camshaft Drive Type ............... Helical gear driven directly from crankshaft
Intake Valve Configuration ............... Overhead valve
Exhaust Valve Configuration ............... Overhead valve
Valves Per Cylinder ............... 2 valves
Cylinder Block Type ............... Cast iron dry sleeve design
Cylinder Head Type ............... Cast iron cross-flow overhead valve
Lubrication System ............... Full-pressure internal lubrication
Oil Pump Type ............... Gear-driven internal assembly
Oil Filter Type ............... Full-flow element canister spinner
Cooling System ............... Forced liquid circulation with bypass system
Water Pump Type ............... Belt-driven centrifugal impeller
Air Cleaner Type ............... Heavy duty dry type dual stage element
Ignition System Type ............... Battery ignition with distributor assembly
Spark Plug Gap, in (mm) ............... 0.025 (0.635)
Distributor Point Gap, in (mm) ............... 0.020 (0.508)
Starting System ............... 12V electrical positive engagement starter
Electrical System System Voltage ............... 12V negative ground system

Fuel System

Fuel Injection Carburetor Model ............... IH Updraft Single Barrel
Carburetor Venturi Size, in (mm) ............... 1.125 (28.575)
Choke Operation ............... Manual cable actuated butterfly mechanism
Fuel Feed Type ............... Gravity flow assisted by mechanical diaphragm pump
Fuel Pump Operating Pressure, psi (bar) ............... 3.5-5.0 (0.24-0.34)
Fuel Pump Drive Location ............... Camshaft eccentric lobe assembly
Main Jet Type ............... Adjustable needle or variable orifice
Idle Jet Type ............... Fixed orifice standard calibrated jet
Float Setting Height, in (mm) ............... 0.281 (7.137)
Float Drop Clearance, in (mm) ............... 0.500 (12.700)
Air Fuel Mixture Adjustment Screw ............... Needle taper fine thread valve
LP Gas Regulator Stage One Pressure, psi (bar) ............... 4.5-6.0 (0.31-0.41)
LP Gas Vaporizer Configuration ............... Engine coolant jacket heated unit
LP Gas Carburetor Model ............... Century or Ensign updraft gas mixer
Fuel Strainer Element Type ............... Fine mesh brass screen with sediment bowl
Fuel Tank Capacity Gasoline, gal (L) ............... 33.0 (124.9)
Fuel Tank Capacity LP Variant, gal (L) ............... 35.5 (134.4)
Sediment Bowl Drain Thread Size ............... 0.125 in NPT internal thread
Fuel Line Diameter, in (mm) ............... 0.312 (7.925)
Governor Type ............... Mechanical centrifugal flyweight governor
Throttle Bore Diameter, in (mm) ............... 1.375 (34.925)
Choke Bore Diameter, in (mm) ............... 1.500 (38.100)

Dimensions and Weight

Overall Length, in (mm) ............... 38.4 (975)
Overall Width, in (mm) ............... 22.2 (565)
Overall Height, in (mm) ............... 34.6 (880)
Dry Weight Basic, lbs (kg) ............... 685 (310)
Wet Weight Complete, lbs (kg) ............... 742 (335)

Maintenance Data

Service Information

Compression Pressure, Normal Minimum, psi (bar) ............... 115.0 (7.92)
Compression Variation Across Cylinders, psi (bar) ............... 10.0 (0.69)
Oil Pressure at Rated Speed, psi (bar) ............... 30.0-45.0 (2.06-3.10)
Oil Pressure at Idle Speed, psi (bar) ............... 10.0 (0.69)
Thermostat Start To Open Temp, F (C) ............... 170.0 (76.6)
Thermostat Fully Open Temp, F (C) ............... 190.0 (87.7)
Radiator Cap Pressure Rating, psi (bar) ............... 7.0 (0.48)
Fan Belt Deflection Standard, in (mm) ............... 0.500 (12.700)
Ignition Advance Centrifugal Maximum, deg ............... 26
Ignition Advance Initial Static Setting, deg ............... 4.0 BTDC
Distributor Dwell Angle Configuration, deg ............... 31-34
Intake Valve Lash, Cold, in (mm) ............... 0.015 (0.381)
Exhaust Valve Lash, Cold, in (mm) ............... 0.015 (0.381)

Engine Oil and Coolant

Engine Oil Type .................. SAE 30, SAE 10W-30, or 15W-40
API Service Classifications ......................... MS, DG, DM
Engine Oil Capacity with Filter, qt (L) ............... 9.0 (8.52)
Engine Oil Capacity Base Pan, qt (L) ............... 8.0 (7.57)
Coolant System Capacity, qt (L) ............... 20.5 (19.40)

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) ............... 3.5625-3.5635 (90.487-90.513)
Cylinder Bore Out of Round, in (mm) ............... 0.0010 (0.0254)
Cylinder Sleeve Out of Round, in (mm) ............... 0.0015 (0.0381)
Cylinder Head Distortion Surface Flatness Max, in (mm) ............... 0.0030 (0.0762)
Cylinder Block Deck Distortion Flatness Max, in (mm) ............... 0.0040 (0.1016)
Main Journal Bearing Clearance, in (mm) ............... 0.0018-0.0036 (0.0457-0.0914)
Main Journal Base Outer Diameter, in (mm) ............... 2.7485-2.7495 (69.8119-69.8373)
Connecting Rod Journal Outer Diameter, in (mm) ............... 2.2485-2.2495 (57.1119-57.1373)
Con Rod Bearing Clearance, in (mm) ............... 0.0015-0.0032 (0.0381-0.0813)
Con Rod Alignment Side Clearance Big End, in (mm) ............... 0.0070-0.0130 (0.1778-0.3302)
Crankshaft End Play, in (mm) ............... 0.0040-0.0080 (0.1016-0.2032)
Piston Clearance In Replaceable Cylinder, in (mm) ............... 0.0035-0.0045 (0.0889-0.1143)
Piston Pin Diameter, in (mm) ............... 1.0000-1.0003 (25.4000-25.4076)
Piston Pin Clearance In Piston Boss, in (mm) ............... 0.0001-0.0003 (0.00254-0.00762)
Piston Pin Bushing Inside Diameter Small End, in (mm) ............... 1.0005-1.0009 (25.4127-25.4228)
Piston Pin Clearance In Connecting Rod, in (mm) ............... 0.0002-0.0006 (0.00508-0.01524)
Top Ring Groove Width, in (mm) ............... 0.0950-0.0960 (2.4130-2.4384)
Second Ring Groove Width, in (mm) ............... 0.0950-0.0960 (2.4130-2.4384)
Oil Ring Groove Width, in (mm) ............... 0.1885-0.1895 (4.7879-4.8133)
Top Ring Side Clearance, in (mm) ............... 0.0020-0.0040 (0.0508-0.1016)
Second Ring Side Clearance, in (mm) ............... 0.0015-0.0035 (0.0381-0.0889)
Oil Ring Side Clearance, in (mm) ............... 0.0015-0.0030 (0.0381-0.0762)
Top Ring End Gap, in (mm) ............... 0.0100-0.0200 (0.2540-0.5080)
Second Ring End Gap, in (mm) ............... 0.0100-0.0200 (0.2540-0.5080)
Oil Ring End Gap, in (mm) ............... 0.0150-0.0300 (0.3810-0.7620)
Intake Valve Stem Outer Diameter, in (mm) ............... 0.3410-0.3418 (8.6614-8.6817)
Exhaust Valve Stem Outer Diameter, in (mm) ............... 0.3400-0.3408 (8.6360-8.6563)
Valve Guide Inside Diameter, in (mm) ............... 0.3433-0.3443 (8.7198-8.7452)
Intake Valve Stem To Guide Clearance, in (mm) ............... 0.0015-0.0033 (0.0381-0.0838)
Exhaust Valve Stem To Guide Clearance, in (mm) ............... 0.0025-0.0043 (0.0635-0.1092)
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) ............... 2.155 (54.737)
Camshaft Journal Outer Diameter (N1), in (mm) ............... 2.1230-2.1240 (53.9242-53.9496)
Camshaft Journal Outer Diameter (N2), in (mm) ............... 2.0605-2.0615 (52.3367-52.3621)
Camshaft Journal Outer Diameter (N3), in (mm) ............... 1.9980-1.9990 (50.7492-50.7746)
Camshaft Journal Outer Diameter (N4), in (mm) ............... 1.8730-1.8740 (47.5742-47.5996)
Camshaft Bearing Radial 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 Height (Intake), in (mm) ............... 0.2850 (7.2390)
Cam Lobe Height (Exhaust), in (mm) ............... 0.2850 (7.2390)
Rocker Arm Shaft Outer Diameter, in (mm) ............... 0.7485-0.7495 (19.0119-19.0373)
Rocker Arm Bushing Inside Diameter, in (mm) ............... 0.7505-0.7515 (19.0627-19.0881)
Rocker Arm To Shaft Running Clearance, in (mm) ............... 0.0010-0.0030 (0.0254-0.0762)
Tappet Lifter Barrel Outer Diameter, in (mm) ............... 0.9985-0.9990 (25.3619-25.3746)
Tappet Lifter Bore Inside Diameter Block, in (mm) ............... 1.0000-1.0010 (25.4000-25.4254)
Tappet Lifter To Block Bore Clearance, in (mm) ............... 0.0010-0.0025 (0.0254-0.0635)
Timing Gear Backlash Engine Gear Train, in (mm) ............... 0.0030-0.0060 (0.0762-0.1524)

Tightening Torques

Cylinder Head Bolts, Step One, lb-ft (Nm) ............... 45.0 (61.0)
Cylinder Head Bolts, Step Two, lb-ft (Nm) ............... 85.0 (115.2)
Cylinder Head Bolts, Final Step, lb-ft (Nm) ............... 115.0 (155.9)
Connecting Rod Cap Nuts, lb-ft (Nm) ............... 55.0 (74.6)
Main Bearing Cap Bolts, lb-ft (Nm) ............... 110.0 (149.1)
Flywheel To Crankshaft Mount Bolts, lb-ft (Nm) ............... 75.0 (101.7)
Vibration Damper Crankshaft Front Pulley Bolt, lb-ft (Nm) ............... 140.0 (189.8)
Camshaft Thrust Plate Small Screws, lb-ft (Nm) ............... 18.0 (24.4)
Camshaft Timing Gear Large Lock Nut, lb-ft (Nm) ............... 85.0 (115.2)
Rocker Arm Shaft Support Bracket Nuts, lb-ft (Nm) ............... 30.0 (40.7)
Spark Plugs, lb-ft (Nm) ............... 25.0 (33.9)
Oil Pan Peripheral Small Bolts, lb-ft (Nm) ............... 14.0 (19.0)
Oil Pan Center Bottom Oil Drain Plug, lb-ft (Nm) ............... 45.0 (61.0)
Timing Gear Front Cover Plate Bolts, lb-ft (Nm) ............... 22.0 (29.8)
Water Pump To Cylinder Block Bolts, lb-ft (Nm) ............... 25.0 (33.9)
Intake And Exhaust Combination Manifold Nuts, lb-ft (Nm) ............... 35.0 (47.5)
Flywheel Housing Rear Frame Engine Bolts, lb-ft (Nm) ............... 65.0 (88.1)
Distributor Clamp Single Lock Bolt, lb-ft (Nm) ............... 12.0 (16.3)
Fuel Diaphragm Pump Flange Mounting Bolts, lb-ft (Nm) ............... 15.0 (20.3)
Oil Pump Cover Secure Plate Screws, lb-ft (Nm) ............... 10.0 (13.6)
Oil Pump Pick Up Screen Tube Bracket Bolt, lb-ft (Nm) ............... 18.0 (24.4)
Valve Rocker Box Top Cover Thumb Nuts, lb-ft (Nm) ............... 8.0 (10.8)
Governor Housing Mount Flange Screws, lb-ft (Nm) ............... 22.0 (29.8)
Water Outlet Thermostat Casing Flange, lb-ft (Nm) ............... 25.0 (33.9)
Carburetor Base Two Bolt Flange Mount Nuts, lb-ft (Nm) ............... 20.0 (27.1)
Air Cleaner Outlet Connecting Hose Clamps, lb-ft (Nm) ............... 4.5 (6.1)
Exhaust Pipe Flange To Manifold Stud Nuts, lb-ft (Nm) ............... 30.0 (40.7)
Generator Alternator Pivoting Adjusting Link Bolt, lb-ft (Nm) ............... 28.0 (38.0)
Starter Motor Nose Housing Flange Bolts, lb-ft (Nm) ............... 45.0 (61.0)
Oil Filter Canister Central Bolt, lb-ft (Nm) ............... 25.0 (33.9)
Crankcase Breather Pipe Mounting Screw, lb-ft (Nm) ............... 12.0 (16.3)
Fan Blade Metal Hub Attaching Water Pump Bolts, lb-ft (Nm) ............... 18.0 (24.4)
Oil Pressure Gallery Hex End Sealing Pipe Plugs, lb-ft (Nm) ............... 20.0 (27.1)

________________________________________________________________________________________

• International Engines Specs
  
• International C175 Specs
  
• International C221 Specs
  
• International C291 Specs
  
• International C301 Specs
  

______________________________________________________________________________________

________________________________________________________________________________________

_______________________________________________________________________________________

________________________________________________________________________________________

________________________________________________________________________________________

________________________________________________________________________________________

________________________________________________________________________________________

________________________________________________________________________________________

________________________________________________________________________________________