| Engine code (located on the cylinder block next to the dipstick) | STR, N-STR, SFA, SF, 4AB, 4BA, 4CA |
| Number of cylinders | 4 in a row |
| The order of operation of the cylinders | 1–3–4–2 |
| Cylinder diameter | 94.00 mm |
| piston stroke | 90.0 mm |
| Working volume | 2499 cm3 |
| Compression ratio | 23,0 |
| Pressure when cranking the engine with a starter | 20 – 25 |
| Power kW/hp: | |
| – STR engine | 51/69 at 4200 rpm. |
| - SFA engine | 68/92 at 4150 rpm. |
| – SF engine | 85/115 at 4200 rpm. |
| Max Torque: | |
| – STR engine | 148 Nm at 2000 rpm. |
| - SFA engine | 201 Nm at 2000 rpm. |
| – SF engine | 270 Nm at 2200 rpm. |
Cylinder head
The head is made of light alloy with inserted combustion chambers, seats and valve guides.
| Cylinder head height | 90±0.15mm |
| Maximum reduction in head height during machining | 0.5 mm |
| Maximum flatness of the lower plane of the cylinder head | 0.15 mm |
| Arm axle diameter | 18.96 - 19.00 mm |
Cylinder head gasket
The cylinder head gaskets were made of synthetic material and were originally two thicknesses and then three thicknesses. The thickness of the gasket is selected depending on the protrusion of the pistons above the upper plane of the engine block. The thickness of the gasket is identified by the number of notches on its edge.
Piston protrusion | Gasket thickness |
| 0.69 to 0.79 mm | 1.53 mm (designation: 2 notches) |
| 0.79 to 0.89 mm | 1.63mm (designation: 3 notches) |
| over 0.89 mm | 1.73mm (designation: 4 notches) |
Only new types of gaskets are manufactured as spare parts (three thicknesses).
Combustion chambers
Swirl combustion chambers, steel, inserted into the cylinder head and fixed with a ball.
| Combustion chamber type | vortex Ricardo Comet Mark V |
| ball diameter | 3 mm |
| Protrusion of swirl chambers from the bottom plane of the cylinder head | 0 - 0.03 mm |
Valve seats
The valve seats are pressed into the cylinder head.
| Valve seat angle: | |
| - inlet | 120° |
| - graduation | 90° |
| Chamfer Width | 2.2 - 2.5 mm |
Valve guides
The valve guides are pressed into the cylinder head and are the same for both intake and exhaust valves.
| Outside diameter: | |
| - nominal | 14.048 - 14.059 mm |
| - the first repair | 14.280 - 14.290 mm |
| - second repair | 14.579 - 14.590 mm |
| Inner diameter | 8.520 - 8.542 mm |
| Length | 55 mm |
| Distance between the guide and the lower plane of the cylinder head | 27.95 - 28.05 mm |
Valves
The valves are installed in the cylinder head vertically and parallel to each other (at right angles to the bottom plane of the cylinder head).
| Chamfer Angle: | |
| - inlet valve | 120° |
| - exhaust valve | 90° |
| Working clearance of valves on a cold engine (four hours after the last launch): | |
| – naturally aspirated engine: | |
| inlet valve | 0.30 - 0.35 mm |
| Exhaust valve | 0.30 - 0.35 mm |
| – turbocharged engine: | |
| inlet valve | 0.10 - 0.20 mm |
| Exhaust valve | 0.20 - 0.30 mm |
| Valve lift: | |
| - inlet valve | 8,95 (Turbo 8,48) mm |
| - Exhaust valve | 8,22 (Turbo 8,27) mm |
| Distance from the bottom plane of the cylinder head to the valve disc: | |
| - inlet valve | 0.75 - 1.25 mm |
| - Exhaust valve | 1.05 - 1.45 mm |
Valve sizes
| Inlet valve: | |
| - length | 116.25 mm |
| - diameter of the valve disc | 42.5 mm |
| – rod diameter | 8.473 - 8.495 mm |
| - thickness of the working edge of the valve disc | 2.2 - 2.5 mm |
| Exhaust valve: | |
| - length | 116.25 mm |
| - diameter of the valve disc | 35.5mm |
| – rod diameter | 8.453 - 8.475 mm |
| - thickness of the working edge of the valve disc | 2.2 - 2.5 mm |
| Maximum allowable clearance between valve stem and guide sleeve | 0.15 mm |
Valve springs
| Spring free length: | |
| – external | 44.6 mm |
| – internal | 41.0 mm |
| Spring wire diameter: | |
| – external | 4.6 mm |
| – internal | 2.4mm |
Engine block
The engine block is made of cast iron.
| Number of main journals | 5 |
| Cylinder diameter: | |
| – nominal class A | 94.000 – 94.015 mm |
| – nominal class B | 94.015 - 94.030 mm |
| – repair 1 class C | 94.200 - 94.215 mm |
| – repair 1 class D | 94.215 - 94.230 mm |
| – repair class 2 E | 94.400 - 94.415 mm |
| – repair class 2 F | 94.415 - 94.430 mm |
| – repair class 3 G | 94.600 - 94.615 mm |
| – repair class 3 H | 94.615 - 94.630 mm |
| – repair 4 class S | 94.800 - 94.815 mm |
| – repair class 4 K | 94.815 - 94.830 mm |
| Pusher seat diameter: | |
| - nominal | 24.00 - 24.03 mm |
| - repair | 24.20 - 24.23 mm |
| Gap between pusher and socket | 0.04 - 0.08 mm |
Crank mechanism
Crankshaft
| Number of root journals | 5 |
| Axial play of the crankshaft | 0.08 - 0.29 mm |
| Locking against axial movement | persistent half rings |
| Thickness of thrust half rings: | |
| – nominal | 2.30 - 2.33 mm |
| – repair | 2.50 - 2.53 mm |
| Clearance in main bearings | 0.040 - 0.098 mm |
| Diameter of main journals: | |
| – standard | 59.994 - 60.021 mm |
| – reduced by 0.30 mm | 59.694 - 59.721 mm |
| – reduced by 0.50 mm | 59.494 - 59.521 mm |
| – reduced by 0.80 mm | 59.194 - 59.221 mm |
| Neck length: | |
| – front | 38.40 - 38.55 mm |
| - intermediate | 30.4 - 30.6 mm |
| – central | 37.76 - 37.81 mm |
| - rear | 37.84 - 38.04 mm |
| Gap in necks | 0.040 - 0.098 mm |
| Diameter of connecting rod journals: | |
| - nominal | 54.994 - 55.021 mm |
| - repair (-0,3) | 54.694 - 54.721 mm |
| Neck length | 36.0 - 36.1 mm |
| Connecting rod bearing width | 29.0 mm |
| Maximum cranking force | 60 Nm |
Indigenous liners
These are thin-walled liners with a steel sheet shell and anti-friction material made of zinc-aluminum alloy.
| Earbud Width: | |
| - front, middle and rear | 29.80 mm |
| – intermediate | 21.80 mm |
Connecting rods
| Connecting rod head hole: | |
| – top (under the sleeve) | 32.975 – 33.000 mm |
| - bottom | 58.737 - 58.750 mm |
| Connecting rod bushing: | |
| - inner diameter | 30.007 - 30.020 mm |
| - outside diameter | 33.000 – 33.025 mm |
| Axial clearance on the crankshaft journal | 0.10 - 0.25 mm |
| Clearance between bushing and crankpin | 0.040 - 0.092 mm |
Piston pins
The pin is made of steel and surface hardened. The pin rotates in the piston and connecting rod head bushing (the so-called floating finger) and is fixed from longitudinal movement by two spring retaining rings.
| Finger diameter: | |
| – STR engine | 29.994 – 30.000 mm |
| - SFA engine | 32,000 mm |
Pistons
The pistons are made of aluminum-silicon alloy. The maximum difference between the masses of the engine piston set must not exceed 5 g.
Installation method in the cylinder: depressions in the bottom of the piston (for valve discs and combustion chamber) should be on the fuel pump side.
| Piston diameter (measurements are taken at a distance of 15.8 mm from the piston crown perpendicular to the piston pin): | |
| – nominal class A | 93.855 – 93.900 mm |
| – nominal class B | 93.900 - 93.915 mm |
| – repair 1 class C | 94.085 – 94.100 mm |
| – repair 1 class D | 94.100 - 94.115 mm |
| – repair class 2 E | 94.285 – 94.300 mm |
| – repair class 2 F | 94.300 - 94.315 mm |
| – repair class 3 G | 94.485 – 94.500 mm |
| – repair class 3 H | 94.500 - 94.515 mm |
| – repair 4 class S | 94.685 – 94.700 mm |
| – repair class 4 K | 94.700 - 94.715 mm |
| Piston protrusion from engine block | 0.50 - 0.92 mm (Turbo 0.40 - 0.87 mm) |
Piston rings
Each piston has two sealing rings and one oil scraper, consisting of three parts.
| Piston rings: | |
| – sealing top | chrome plated, spherical |
| – compression | notched (up) |
| – oil scraper | U-shaped |
| Piston ring gaps (installed in the cylinder): | |
| – top sealing ring | 0.40 - 0.65 mm (Turbo 0.25 - 0.50 mm) |
| - compression ring | 0.35 - 0.60 mm (Turbo 0.20 - 0.40 mm) |
| - oil scraper ring | 0.15 - 0.30 mm (Turbo 0.15 - 0.45 mm) |
| Ring height: | |
| – sealing top | 1.978 - 1.990 mm |
| – compression | 1.978 - 1.990 mm |
| – oil scraper | 4.478 - 4.490 mm |
Gas distribution system
The gas distribution system includes a camshaft installed in the cylinder block, pushers, pusher rods, valve and valve levers.
The camshaft is driven by a double row chain from the crankshaft.
| Valve timing: | |
| - opening intake valves | 8°before TDC |
| - closing intake valves | 40°after BDC |
| - opening intake valves | 56°before BDC |
| - closing intake valves | 12°after TDC |
TDC and BDC respectively top and bottom dead center.
Camshaft
The camshaft rotates in three chain-driven bearings.
| Camshaft journal diameters | 41.925 – 41.950 mm |
| Operating clearance of the camshaft journals | 0.05 - 0.11 mm |
| Camshaft end play | 0.05 - 0.15 mm |
Lubrication system
Pressure lubrication is provided by a gear oil pump driven by the camshaft through an angle gear. The lubrication system has a replaceable filter and an oil cooler.
| Oil pump type | gear |
| Engine oil volume: | |
| - without a filter | 5.0 dm3 |
| – with filter | 5.6 dm3 |
| Engine oil type | API SE/CD or SF/CD |
| Viscosity of engine oil at temperature: | |
| – from 20°С to +30°С | SAE 10W-30 |
| – above -20°C | SAE 10W-40/ 10W-50 |
| – above -15°С | SAE 15W-40/ 15W-50 |
| – below -20°С | 5W-30 |
| Replacement frequency | every 7500 km or every six months |
Oil pressure sensor
The oil pressure sensor is located in the oil filter holder.
| Pilot light pressure | 0.08 - 0.10 MPa |
Cooling system
The closed cooling circuit with antifreeze liquid circulating under pressure contains a radiator, an expansion tank and a coolant pump. Air is removed from the system automatically after starting the engine.
Coolant pump
The centrifugal coolant pump, located on the front wall of the cylinder block, is driven by a V-belt. The coolant pump is not repairable and must be replaced if it malfunctions.
| Rotor diameter | 60 mm |
Thermostat
The wax thermostat is located in the same housing as the coolant pump.
| Brand | Calorstat |
| Opening start temperature | 72°С |
| Full opening temperature | 81°С |
| Minimum valve travel | 7.5mm |
Coolant
| Quantity | 9.5 dm3 |
| Type | special antifreeze fluid Ford SQM 97 B 9103A |
| Service interval | level check every 7500 km (does not require periodic replacement of the coolant) |
Fuel system
The fuel system contains a CAV Roto Diesel fuel distribution pump.
Fuel pump
The Roto Diesel rotary fuel injection pump is equipped with a hydraulic cold start booster with thermostatically controlled automatic high idle support and an engine shutdown solenoid valve (STOP valve), shutting off the fuel supply.
| Brand and type | Roto Diesel or Lucas Roto Diesel |
| injection order (cylinder #1 flywheel side) | 1–3–4–2 |
| Start of injection | piston position of the 1st cylinder of the engine 2.85 mm before TDC or 18°before TDC |
| Idling speed: | |
| - no boost | 800 rpm |
| - turbocharged | 875 - 900 rpm. |
| Fast idle speed (cold engine) | 880 - 930 rpm. |
| Max RPM (without load) | 4800 - 4850 rpm. |
| Deceleration time from maximum to idle | 5 second |
| Turbocharger | Garret AiResearch T03 |
Nozzles
The injectors are screwed into the cylinder head.
| nozzle body | Roto Diesel or Bosch KSA 30 S 44 |
| Nozzle opening pressure: | |
| - no boost | 11.5±0.5 MPa |
| - turbocharged | 13.0±0.5 MPa |
Glow plugs
| Brand and type | Bosch, Beru, Lucas or Champion CH68 |
| Control temperature of heating candles (within 7 seconds at an ambient temperature of 20°C) | 850°С |
Tightening torques
| Bolts of fastening of a head of the block of cylinders: | |
| - Stage 1 | 30 Nm |
| – stage 2 | 70 Nm |
| – Stage 3 – unscrew the bolts in tightening order by 90°and re-tighten | 70 Nm |
| - Stage 4 - after 10 minutes of engine operation at 3000 rpm and cooling for 4 hours and tighten twice (once *) (unscrew 90°and tighten) | 70*/ 80 Nm |
| – Stage 5 | tighten by 120° |
| Locknuts of adjusting bolts of levers | 12.5 - 17.5 Nm |
| cylinder head cover | 3 – 4 Nm |
| Nuts of internal racks of an axis of levers | 17 - 22 Nm |
| Pusher cover | 5 - 7.5 Nm |
| Oil drain plug | 7.5 - 12.5 Nm |
| oil receiver | 5 - 7.5 Nm |
| Oil gauge pipe | 20 – 30 Nm |
| Main bearing caps | 100 – 120 Nm |
| Connecting rod bearing caps | 53 - 62 Nm |
| Flywheel: | |
| - Stage 1 | 15 Nm |
| – stage 2 | 95 Nm |
| crankshaft pulley | 240 - 260 Nm |
| Oil pump | 25 – 30 Nm |
| Oil pump plugs | 80 – 100 Nm |
| Oil pump cover | 5 - 7.5 Nm |
| Engine lifting bracket | 10 – 12 Nm |
| Coolant drain plug on cylinder block | 20 – 30 Nm |
| Radiator fan clutch nut | 30 – 40 Nm |
| Alternator belt tensioner fastening | 21 -25 Nm |
| glow plugs | 30 – 40 Nm |
| Gearbox to engine: | |
| – type N | 40 – 50 Nm |
| – type MT-75 | 70 – 90 Nm |
* Applies to 70mm and 95mm bolts only.
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