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Ford LRG-425 Engine

General Technical Data

Engine Specifications

Engine Model ............... Ford LRG-425
Engine Type ............... 4-cycle inline 4-cylinder spark-ignition liquid-cooled multi-fuel engine
Number of Cylinders ............... 4
Cylinder Arrangement ............... In-line
Valvetrain Configuration ............... Overhead Camshaft OHC
Number of Valves per Cylinder ............... 2
Total Number of Valves ............... 8
Engine Bore, in (mm) ............... 3.78 (96.0)
Engine Stroke, in (mm) ............... 3.40 (86.3)
Displacement, cu.in (L) ............... 153 (2.5)
Rated Power (Gasoline), hp (kW) ............... 74 (55) at 3600 rpm
Rated Power (Natural Gas), hp (kW) ............... 63 (47) at 3600 rpm
Peak Torque (Gasoline), lb-ft (Nm) ............... 123 (167) at 1800 rpm
Peak Torque (Natural Gas), lb-ft (Nm) ............... 115 (156) at 2600 rpm
Governed Speed, rpm ............... 1500-3600
Idle Speed, rpm ............... 750-900
Compression Ratio ............... 9.37:1
Firing Order ............... 1-3-4-2
Valve Tappet Type ............... Hydraulic roller followers
Exhaust Valve Seat Inserts ............... Heavy-duty hardened alloy
Crankshaft Design ............... Fully counterweighted cast iron
Cylinder Head Design ............... Cross-flow design
Camshaft Drive ............... Synchronous Timing Belt
Cylinder Block Material ............... Cast iron
Cylinder Head Material ............... Cast iron
Lubrication System ............... Full-pressure lubrication
Oil Pump Type ............... Rotor-type gear-driven pump
Oil Filter Type ............... Full-flow spin-on cartridge
Cooling System ............... Liquid forced circulation
Water Pump Type ............... Belt-driven centrifugal pump
Air Cleaner Type ............... Dry-type replacement element
Ignition Systeme ............... Distributorless Electronic Ignition System DIS
Starting System ............... Electric starter motor
Electrical System, V ............... 12
Alternator Rating, A ............... 50-95

Fuel System

Primary Fuel Capabilities ............... Unleaded gasoline liquefied petroleum gas LPG natural gas NG
Gasoline Specification ............... 87 AKI minimum octane rating
Natural Gas Heat Content Value, BTU/cu.ft ............... 1050
LPG Specification ............... HD-5 propane standard industrial grade
Fuel Delivery Configurations ............... Carbureted downdraft or Electronic Fuel Injection EFI
Carburetor Manufacturer Model ............... Zenith downdraft mechanical governor variant
EFI Injection Type ............... Multi-port electronic fuel injection
Fuel Pressure Gasoline EFI, psi (kPa) ............... 39.1-40.6 (270-280)
Fuel Filter Location Carbureted ............... Integrated at carburetor inlet pipe
Fuel Filter Location EFI ............... Inline high-pressure chassis mount
LPG Vaporizer Regulator Type ............... Two-stage heated pressure reduction unit
Natural Gas Regulator Type ............... Secondary demand regulator assembly
Fuel Shutoff Valve Type ............... 12V solenoid electronic control lockoff
Air-Fuel Ratio Control ............... Closed-loop oxygen sensor feedback for EFI models
Throttle Body Bore Diameter, in (mm) ............... 1.96 (50.0)
Fuel Injector Resistance, ohms ............... 12.0-16.0
Gaseous Fuel Carburetor Type ............... Venturi-style mixer unit
Governor System Option 1 ............... Electronic governor package
Governor System Option 2 ............... Mechanical flyweight governor belt-driven
Governor Regulation Percentage ............... 3-5 percent stability standard
Maximum Fuel Inlet Pressure Gaseous, in H2O (kPa) ............... 11.0-14.0 (2.74-3.48)
Minimum Fuel Inlet Pressure Gaseous, in H2O (kPa) ............... 7.0 (1.74)
Specific Fuel Consumption, Gasoline, lb/hp-hr (g/kW-hr) ............... 0.46 (280)
Specific Fuel Consumption, LPG, lb/hp-hr (g/kW-hr) ............... 0.49 (298)

Dimensions and Weight

Overall Engine Length, in (mm) ............... 26.5 (675)
Overall Engine Width, in (mm) ............... 21.4 (545)
Overall Engine Height, in (mm) ............... 26.9 (685)
Dry Weight, lbs (kg) ............... 339 (154)
Shipping Weight, lbs (kg) ............... 435 (197)

Maintenance Data

Service Information

Compression Pressure Standard Range, psi (bar) ............... 150-185 (10.3-12.7)
Minimum Acceptable Compression Pressure, psi (bar) ............... 120 (8.3)
Compression Variation Between Cylinders, percent ............... 15
Minimum Oil Pressure at Idle Speed, psi (kPa) ............... 15 (103.4)
Standard Oil Pressure at 2500 rpm, psi (kPa) ............... 40-60 (275.8-413.7)
Thermostat Opening Temperature, F (C) ............... 192 (89)
Thermostat Full Open Temperature, F (C) ............... 212 (100)
Spark Plug Gap, in (mm) ............... 0.042-0.046 (1.07-1.17)

Engine Oil and Coolant

Engine Oil Type .................. SAE 5W-30, SAE 10W-30, SAE 15W-40
API Service Classifications ......................... SG, SH, or SJ
Engine Oil Capacity with Filter, qts (L) ............... 4.5 (4.26)
Engine Oil Capacity without Filter, qts (L) ............... 4.0 (3.78)
Cooling System Fluid Capacity, qts (L) ............... 8.5 (8.05)

Service Intervals

Change engine oil ............... Every 150 hours
Replace oil filter ............... Every 150 hours
Replace fuel filter ............... Every 300 hours
Inspect air filter ............... Every 50 hours
Replace air filter ............... Every 300 hours
Change coolant ............... Every 1000 hours
Valve-lash adjustment ............... Every 300 hours
Check fuel system ............... Every 1000 hours
Replace spark plug ............... Every 500 hours
Compression test ............... Every 1000 hours
Belt inspection ............... Every 150 hours

Service Specifications

Cylinder Bore Inside Diameter, in (mm) ............... 3.7795-3.7807 (96.000-96.030)
Cylinder Bore Maximum Out-of-Round, in (mm) ............... 0.0015 (0.038)
Cylinder Bore Maximum Taper, in (mm) ............... 0.0010 (0.025)
Connecting Rod Journal Diameter, in (mm) ............... 2.046-2.047 (51.98-52.00)
Main Bearing Journal Diameter, in (mm) ............... 2.282-2.283 (57.98-58.00)
Crankshaft End Play, in (mm) ............... 0.004-0.008 (0.10-0.20)
Connecting Rod Journal Clearance, in (mm) ............... 0.0014-0.0028 (0.036-0.071)
Connecting Rod Side Clearance, in (mm) ............... 0.0045-0.0105 (0.114-0.267)
Main Bearing Journal Clearance, in (mm) ............... 0.0015-0.0031 (0.038-0.079)
Crankshaft End Play, in (mm) ............... 0.012 (0.305)
Main Bearing Bore Inside Diameter, in (mm) ............... 2.441-2.442 (62.00-62.03)
Connecting Rod Big End Bore Inside Diameter, in (mm) ............... 2.165-2.166 (55.00-55.02)
Connecting Rod Small End Bushing I.D, in (mm) ............... 0.9128-0.9134 (23.185-23.200)
Piston to Cylinder Wall Clearance, in (mm) ............... 0.0012-0.0020 (0.030-0.051)
Piston Skirt Outer Diameter, in (mm) ............... 3.7781-3.7789 (95.964-95.984)
Piston Pin Bore Inside Diameter, in (mm) ............... 0.9122-0.9125 (23.170-23.177)
Piston Pin to Piston Pin Bore Clearance, in (mm) ............... 0.0003-0.0006 (0.008-0.015)
Top Ring Side Clearance, in (mm) ............... 0.0020-0.0038 (0.051-0.096)
Second Ring Side Clearance, in (mm) ............... 0.0016-0.0034 (0.041-0.086)
Oil Ring Side Clearance, in (mm) ............... 0.0015-0.0035 (0.038-0.089)
Top Ring End Gap, in (mm) ............... 0.010-0.020 (0.254-0.508)
Second Ring End Gap, in (mm) ............... 0.012-0.022 (0.305-0.559)
Oil Ring End Gap, in (mm) ............... 0.015-0.035 (0.381-0.889)
Cylinder Block Deck Surface Flatness, in (mm) ............... 0.003 (0.076)
Cylinder Head Deck Flatness, in (mm) ............... 0.004 (0.101)
Intake Valve Head Diameter, in (mm) ............... 1.73 (43.9)
Exhaust Valve Head Diameter, in (mm) ............... 1.46 (37.1)
Intake Valve Stem Outer Diameter, in (mm) ............... 0.3150-0.3156 (8.001-8.016)
Exhaust Valve Stem Outer Diameter, in (mm) ............... 0.3142-0.3148 (7.981-7.996)
Intake Valve Stem to Guide Clearance, in (mm) ............... 0.0010-0.0024 (0.025-0.061)
Exhaust Valve Stem to Guide Clearance, in (mm) ............... 0.0016-0.0032 (0.041-0.081)
Valve Face Angle, degrees ............... 45
Valve Seat Angle, degrees ............... 45
Valve Guide Inside Diameter, in (mm) ............... 0.3166-0.3174 (8.042-8.062)
Valve Spring Free Length, in (mm) ............... 1.88 (47.75)
Camshaft Journal Bore Inside Diameter, in (mm) ............... 1.773-1.775 (45.03-45.08)
Camshaft Journal Clearance, in (mm) ............... 0.0016-0.0032 (0.041-0.081)
Camshaft Journal Diameter, in (mm) ............... 1.771-1.772 (44.98-45.00)
Camshaft End Play, in (mm) ............... 0.003-0.007 (0.076-0.178)
Oil Pump Rotor Outer Body Clearance, in (mm) ............... 0.005-0.009 (0.127-0.229)
Oil Pump Inner to Outer Rotor Clearance, in (mm) ............... 0.002-0.006 (0.051-0.152)

Tightening Torques

Cylinder Head Bolts (Step 1), lb-ft (Nm) ............... 50 (68)
Cylinder Head Bolts (Step 2), lb-ft (Nm) ............... 70 (95)
Cylinder Head Bolts (Step 3), lb-ft (Nm) ............... 85-92 (115-125)
Main Bearing Cap Bolts, lb-ft (Nm) ............... 80-88 (108-119)
Connecting Rod Cap Nuts (Step 1), lb-ft (Nm) ............... 25 (34)
Connecting Rod Cap Nuts (Step 1), lb-ft (Nm) ............... 40-45 (54-61)
Flywheel to Crankshaft Bolts, lb-ft (Nm) ............... 55-60 (75-81)
Camshaft Sprocket Gear Bolt, lb-ft (Nm) ............... 52-58 (70-79)
Crankshaft Damper Pulley Bolt, lb-ft (Nm) ............... 105-115 (142-156)
Rocker Arm Cover Valve Cover Screws, lb-in (Nm) ............... 70-90 (8-10)
Oil Pan to Block Retaining Bolts, lb-in (Nm) ............... 140-165 (16-19)
Oil Pan Drain Plug, lb-ft (Nm) ............... 15-23 (20-31)
Water Pump Assembly to Block Screws, lb-ft (Nm) ............... 15-18 (20-24)
Intake Manifold Fasteners, lb-ft (Nm) ............... 15-18 (20-24)
Exhaust Manifold Fasteners, lb-ft (Nm) ............... 16-20 (22-27)
Spark Plugs Installation, lb-ft (Nm) ............... 15-20 (20-27)
Timing Belt Cover Screws, lb-in (Nm) ............... 60-80 (7-9)
Camshaft Rear Thrust Plate Screws, lb-in (Nm) ............... 70-90 (8-10)
Oil Pump Screen and Pickup Tube Bolt, lb-ft (Nm) ............... 12-15 (16-20)
Oil Pump Assembly Body to Block Fasteners, lb-ft (Nm) ............... 14-18 (19-24)
Alternator Mounting Bracket Primary Bolt, lb-ft (Nm) ............... 28-35 (38-47)
Starter Motor Mounting Stud Nuts and Bolts, lb-ft (Nm) ............... 15-20 (20-27)
Flywheel Housing Adapter Ring Bolts, lb-ft (Nm) ............... 28-38 (38-51)
Thermostat Housing Water Outlet Screws, lb-ft (Nm) ............... 12-15 (16-20)
Engine Belt Idler Pulley Assembly Fastener, lb-ft (Nm) ............... 25-30 (34-41)
Ignition Control Module Mounting Brackets, lb-in (Nm) ............... 40-60 (4.5-6.8)
Oxygen Sensor Installation, lb-ft (Nm) ............... 26-32 (35-43)
Fuel Rail Assembly Attachment Fasteners, lb-in (Nm) ............... 70-100 (8-11)
Throttle Body Attachment Screws, lb-in (Nm) ............... 80-110 (9-12.4)
Governor Drive Housing Assembly Mounting Frame, lb-ft (Nm) ............... 14-18 (19-24)
Distributor Assembly Hold Down Clamp Bolt, lb-ft (Nm) ............... 14-18 (19-24)
Oil Pressure Sensor Sender Switch Main Port, lb-ft (Nm) ............... 10-14 (14-19)
Coolant Temperature Sending Sensor, lb-ft (Nm) ............... 12-16 (16-22)
Crankshaft Front Seal Retainer Plate Screws, lb-in (Nm) ............... 80-110 (9-12.4)
Crankshaft Rear Seal Housing Fasteners, lb-in (Nm) ............... 80-110 (9-12.4)
Engine Lifting Eye Assembly Fasteners, lb-ft (Nm) ............... 25-32 (34-43)

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• Ford Engines Specs
  
• Ford DSG-423 Specs
  
• Ford LRG-425i Specs
  
• Ford LRG-423 Specs
  
• Ford LSG-423 Specs
  

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