Nissan L20B Specifications
| Engine Model: Nissan L20B |
| Engine Type: 4-cycle inline 4-cylinder SOHC 8-valve liquid-cooled gasoline |
| Total Displacement: 119.1 cu.in (1.95 L) |
| Rated Engine Power: 100-110 Hp (75-82 kW) at 5600 rpm |
| Fuel System Type: Twin side-draft or single downdraft carburetor |
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The Nissan L20B is a 2.0-liter inline-four
gasoline engine belonging to the famous and long-lived L-series engine
family, which includes the L13, L14, L16, L18, and L20/L20B engines.
Introduced in the mid-1970s, the L20B quickly became one of the most
respected and widely used four-cylinder engines produced by Nissan,
powering a broad spectrum of passenger cars, commercial vehicles, and
light utility trucks. Known for its exceptional durability, excellent
torque characteristics, mechanical simplicity, and ease of service, the
L20B is still revered among enthusiasts and classic Nissan restorers.
The engine was the largest displacement four-cylinder gasoline engine in
the L-series family and incorporated all the traditional L-series
strengths - cast-iron block, aluminum overhead-cam cylinder head, sturdy
crankshaft, reliable timing chain, and durable lubrication system. Due
to its strong low-end torque and robust construction, the L20B was
widely used not only in daily-use sedans but also in utility trucks and
motorsports applications, including rallying and off-road performance
builds.
Its simplicity, strong aftermarket support, and abundant availability
contribute to its popularity decades later. Many L20B engines are still
running reliably today, often after several rebuilds, showcasing the
legendary engineering of Nissan’s early OHC engines.
The Nissan L20B is a four-stroke, inline-four, water-cooled gasoline
engine with a displacement of 1952 cc, or approximately 119.1 cubic
inches. Its bore and stroke dimensions are 85.0 mm (3.35 inches) and
86.0 mm (3.39 inches), respectively, giving it a slightly undersquare
configuration that enhances torque output. This balanced geometry makes
the engine responsive and tractable across the entire rpm range.
Compression ratio varies depending on market, carburetion, and
emission-tuning versions, generally ranging from 8.4:1 to 9.0:1. Power
output varies by application but ranges between 100 and 110 Hp (75 to 82
kW) at 5600 rpm. Maximum torque values generally fall between 150 and
160 Nm (111 to 118 lb-ft) at around 3600 to 4400 rpm. Idle speed is set
at 700 to 800 rpm. The firing order is 1-3-4-2.
The L20B uses a cast-iron block with excellent structural rigidity and
the capacity to endure repeated overhaul cycles. Cylinder walls are
thick, allowing multiple rebore services during engine rebuilding. The
engine block height (deck height) is increased relative to the L18 to
accommodate the longer stroke, and this taller block became a signature
feature of the L20B’s architecture.
The crankshaft is a forged-steel unit supported by five large main
bearings. This configuration enhances smoothness, contributes to high
durability, and allows consistent high-mileage performance. Connecting
rods are forged steel and designed to handle high stress loads,
especially in applications such as towing or rally competition. Pistons
are lightweight aluminum alloy with conventional three-ring packs
consisting of two compression rings and one oil-control ring. The piston
crown shape supports stable burn characteristics and good torque
development.
The L20B uses an aluminum cylinder head with a single overhead camshaft
(SOHC) design operating two valves per cylinder, for a total of eight
valves. The head design is a wedge-style combustion chamber known for
efficient flame travel, good low-rpm torque, and clean burn
characteristics.
The camshaft is driven by a robust double-row timing chain that provides
outstanding reliability. Timing chains on L-series engines are known to
last extremely long with minimal service, although chain-guide wear and
tensioner checks are recommended at high mileage.
Valve sizes commonly include:
- Intake valve diameter: approx. 42 mm (1.65 inches)
- Exhaust valve diameter: approx. 35 mm (1.38 inches)
Valve lash must be adjusted periodically, as the L20B uses mechanical
rockers and lash pads instead of hydraulic lifters.
Cold valve clearances:
- Intake: 0.25 mm (0.010 inches)
- Exhaust: 0.30 mm (0.012 inches)
The L20B uses a carbureted fuel system.
Depending on market and model, it may use:
- A single downdraft Hitachi carburetor
- Twin Hitachi SU-style side-draft carburetors
- Emissions-controlled feedback carburetors on later North American
models
A mechanical fuel pump mounted on the engine block supplies fuel at low
pressure (2.5 to 4.0 psi). Fuel is filtered using a replaceable
paper-element inline filter.
Carburetor features include:
- Idle mixture circuit
- Main jet(s) and secondary circuits
- Choke mechanism (manual or automatic)
- Accelerator pump
- Vacuum-operated secondary throttle (on select models)
- Anti-dieseling solenoid (emission-era vehicles)
Ignition timing ranges from 8° to 12° BTDC at idle, advancing
mechanically and via vacuum control depending on load and rpm.
The L20B uses a full-pressure wet-sump lubrication system powered by a
trochoid-type oil pump driven from the block. Oil lubrication is
supplied to the crankshaft bearings, connecting rod bearings, camshaft
bearings, timing chain, and valvetrain components.
Oil capacity is 3.8 to 4.0 liters (4.0 to 4.2 U.S. quarts) with filter.
Recommended oil viscosity varies by climate; common grades include SAE
10W-30, 10W-40, and 20W-50.
Oil pressure values:
- At 3000 rpm: 350-450 kPa (50-65 psi)
- At idle: above 70 kPa (10 psi)
Cooling is provided by a belt-driven centrifugal water pump. Coolant
flows through the block, head, radiator, and heater core. Thermostats
begin opening at approximately 82°C (180°F) and fully open near 95°C
(203°F). Cooling system capacity is between 7.0 and 7.5 liters (7.4 to
7.9 U.S. quarts).
Key cooling-system components include:
- Copper/brass or aluminum radiator
- Mechanical radiator fan (some models use fan clutch)
- Bypass circuits for early warm-up
- Overflow reservoir
| Intake and Exhaust Systems |
Induction is provided by aluminum intake manifolds designed to improve
torque delivery. Single-carburetor manifolds emphasize low-rpm torque
and stable idle quality, while dual-SU manifolds provide enhanced flow
for performance applications.
The exhaust manifold is a durable cast-iron design with relatively
equal-length runners for improved gas flow. Performance and motorsport
applications often use tubular headers for increased high-rpm power.
| Ignition and Electrical System |
Ignition is controlled by a distributor
containing:
- Mechanical centrifugal advance mechanism
- Vacuum advance diaphragm
- Breaker points (early models) or electronic module (later models)
Spark plugs used are NGK B6ES or equivalent, with a gap of 0.8 mm (0.031
inches).
Alternators produce between 35 and 50 amperes depending on model year.
Starter motors are robust and suitable for both cold and hot conditions.
Depending on market and year, the L20B may
include:
- PCV (positive crankcase ventilation)
- EGR system
- Air-injection pump (North American versions)
- Activated charcoal EVAP canister
- Anti-dieseling solenoid
- Thermal vacuum valves
- Length: 610-630 mm (24.0-24.8 inches)
- Width: 520-540 mm (20.5-21.3 inches)
- Height: 650-720 mm (25.6-28.3 inches)
Dry weight varies between 150 and 165 kg (331 to 364 lbs), depending on
accessory configuration.
Maintenance intervals:
- Oil and filter change: every 5000-8000 km (3000-5000 miles)
- Air filter: every 20,000 km (12,000 miles)
- Fuel filter: every 20,000-30,000 km
- Spark plugs: every 15,000-20,000 km
- Valve clearance: every 20,000 km
- Timing chain: inspect at high mileage
- Coolant: every 40,000 km or 2 years
- Compression: 150-180 psi (1034-1241 kPa), variation <10% between
cylinders
- Cylinder head bolts: 100 Nm (74 lb-ft)
- Main bearing cap bolts: 80 Nm (59 lb-ft)
- Connecting rod bolts: 54 Nm (40 lb-ft)
- Flywheel bolts: 98 Nm (72 lb-ft)
- Crankshaft pulley bolt: 155 Nm (114 lb-ft)
- Intake manifold bolts: 22 Nm (16 lb-ft)
- Exhaust manifold bolts: 28 Nm (21 lb-ft)
- Spark plugs: 18 Nm (13 lb-ft)
- Oil drain plug: 34 Nm (25 lb-ft)
The Nissan L20B engine powered a large
range of vehicles, including:
- Datsun 610 / Nissan Bluebird-U
- Datsun 710 / Violet
- Datsun 620 pickup
- Nissan A10 / Stanza
- Early Nissan 720 pickup (select markets)
- Nissan Cedric (regional)
- Nissan Laurel (regional trims)
- Numerous commercial vehicles and vans
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