Nissan L20 Specifications
| Engine Model: Nissan L20 |
| Engine Type: 4-cycle inline 6-cylinder SOHC 12-valve liquid-cooled gasoline |
| Total Displacement: 121.9 cu.in (1.99 L) |
| Rated Engine Power: 105-130 Hp (78-97 kW) at 6000 rpm |
| Fuel System Type: Twin side-draft or single downdraft carburetor |
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The Nissan L20 engine represents an important
chapter in the early development of Nissan’s inline-six powerplants.
Produced during the late 1960s and early 1970s, the L20 was a 2.0-liter
member of the L-series engine family, which also included the L16, L18,
L20A, L24, L26, and L28. The L20 (also known as L20A in many markets)
was primarily used in mid-size Japanese sedans and luxury models such as
the Nissan Cedric, Gloria, and Laurel. Unlike the later L24 and L28
engines that became globally famous through the Z-car line, the L20 was
designed for domestic and Asian-market applications where taxation and
vehicle-class regulations favored smaller displacement engines.
Despite its relatively modest displacement, the L20 offered impressive
refinement, smooth operation, and excellent durability - characteristics
typical of Nissan’s inline-six engineering. The L20 shares the same
design philosophy as the larger L-series engines: a cast-iron block,
aluminum overhead-cam (OHC) cylinder head, seven-bearing forged
crankshaft, robust timing chain drive, and solid internal components. It
could be equipped with either carburetors or fuel injection depending on
model and year. The L20 powered luxury sedans, sporty coupes, and
special-edition models, making it one of Nissan’s early premium
powerplants.
The Nissan L20 is a water-cooled, inline-six, four-stroke gasoline
engine. Depending on version and market, it was referred to as L20 or
L20A, though the architecture is fundamentally identical. Total
displacement is 1998 cc (121.9 cubic inches). Bore is 78.0 mm (3.07
inches), and stroke is approximately 69.7 mm (2.74 inches), giving the
L20 a distinctly oversquare configuration that supports high-revving
characteristics and smooth combustion.
Compression ratio varies by year,
carburetor, and emissions configuration:
- Early L20: approx. 9.0:1
- L20A high compression versions: approx. 9.5:1
- Emission-controlled versions: approx. 8.5:1-9.0:1
Power output varies widely by version:
- Early twin-carb versions: approx. 125-130 hp (93-97 kW) at 6000 rpm
- Single-carb versions: approx. 105-115 hp (78-86 kW) at 5600-6000 rpm
- Fuel-injected versions (rare): approx. 120-130 hp
Torque output: 110-125 lb-ft (150-170 Nm) at 3600 rpm. The firing order
for all L20 versions is 1-5-3-6-2-4. Idle speed is 700-800 rpm depending
on carburetion and emissions systems.
The L20 uses a cast-iron block with thick cylinder walls, engineered for
long-term operation and rebuildability. The crankshaft is a forged-steel
six-throw design supported by seven main bearings. The seven main
bearings provide excellent crankshaft rigidity, smooth operation, and
long life even under continuous high-rpm use. The block height is
shorter than the L24/L28 engines, reflecting the shorter stroke and
lower deck design.
The connecting rods are forged steel, and the pistons are aluminum alloy
with a three-ring pack consisting of two compression rings and one
oil-control ring. The pistons are designed with combustion chamber
compatibility for the wedge-type OHC cylinder head. The wrist pins are
full-floating to reduce stress on the piston and rod assembly.
The cylinder head is constructed of cast aluminum alloy using a single
overhead camshaft (SOHC) layout with two valves per cylinder. The
camshaft is driven by a double-row roller timing chain, known for its
exceptional longevity and low maintenance requirements. The chain
tensioner is hydraulic and automatically adjusts to maintain proper
chain tension.
Valve sizes vary slightly across versions:
- Intake valve diameter: approx. 38-40 mm (1.50-1.57 in)
- Exhaust valve diameter: approx. 33-35 mm (1.30-1.38 in)
Valve lash is manually adjustable. Cold
clearances:
- Intake: approx. 0.25 mm (0.010 in)
- Exhaust: approx. 0.30 mm (0.012 in)
Combustion chambers are wedge-shaped, providing efficient flame travel,
reliable combustion at high compression, and stable torque
characteristics.
The L20 was available with several fuel
systems:
1. Single downdraft Hitachi carburetor (most common)
2. Twin sidedraft Hitachi/SU-style carburetors (performance trims)
3. Rare fuel-injected versions in select Japanese luxury trims
Carburetor features include:
- Main, idle, and power circuits
- Mechanical or vacuum secondary (depending on model)
- Automatic or manual choke
- Anti-dieseling solenoid (emission-era versions)
Fuel supply is provided by a mechanical pump driven by the camshaft.
Fuel pressure is 2.5-4.0 psi. A paper-element fuel filter protects jets
from contamination.
The L20 uses a full-pressure wet-sump lubrication system. A
crankshaft-driven gear-type oil pump delivers oil to main bearings,
connecting rod bearings, camshaft journals, rocker arms, and timing
components. Oil galleries are generously sized, supporting long-term
durability.
Oil capacity: 4.5-5.0 liters (4.8-5.3 US quarts) with filter
Recommended viscosity: 10W-30, 10W-40, or 20W-50 depending on climate
and use
Oil pressure:
- 3000 rpm: 350-450 kPa (50-65 psi)
- Idle: >70 kPa (>10 psi)
Cooling is provided by a belt-driven centrifugal water pump. Coolant
circulates through the block, head, radiator, and heater core. Cooling
system capacity: 8.0-8.5 liters (8.5-9.0 US quarts).
Thermostat characteristics:
- Opens at approx. 82°C (180°F)
- Fully open near 95°C (203°F)
Components include:
- Crossflow radiator
- Mechanical cooling fan or fan clutch
- Temperature sensor for gauge
- Optional electric fan on later models
| Intake and Exhaust Systems |
Induction components vary with fuel system. Single-carb models use a
cast-aluminum intake manifold tuned for low- and mid-range torque.
Twin-carb models use improved-flow manifolds suited to performance
applications.
The exhaust manifold is cast iron,
featuring either:
- A two-into-one runner layout for standard trims
- Improved-flow manifolds for twin-carb versions
Performance models often used tubular headers.
| Ignition and Electrical System |
Ignition systems vary:
- Early versions: breaker-point distributor
- Later versions: electronic ignition module
All distributors include:
- Mechanical centrifugal advance
- Vacuum advance diaphragm
Spark plug specification:
- NGK BP6ES or equivalent
- Gap: approx. 0.8 mm (0.031 in)
Electrical charging is handled by a belt-driven alternator producing
35-50 amps depending on trim level.
Depending on era and emissions regulations,
the L20 may include:
- Positive crankcase ventilation (PCV)
- EGR valve
- Charcoal EVAP canister
- Air injection pump (Japan/USA late models)
- Thermal vacuum switching valves
- Length: 700-740 mm (27.6-29.1 in)
- Width: 520-540 mm (20.5-21.3 in)
- Height: 650-700 mm (25.6-27.6 in)
Dry weight: 180-200 kg (397-441 lb) depending on carburetion and
accessories
Recommended intervals:
- Oil and filter: every 5000-8000 km (3000-5000 miles)
- Valve lash: every 20,000 km (12,000 miles)
- Air filter: every 20,000 km
- Fuel filter: every 20,000-30,000 km
- Spark plugs: every 15,000-20,000 km
- Coolant: every 40,000 km or 2 years
- Timing chain: inspect at high mileage
Compression (healthy engine): 150-175 psi (1034-1206 kPa), <10% cylinder
variation
- Cylinder head bolts: approx. 100 Nm (74 lb-ft)
- Main bearing caps: approx. 85 Nm (63 lb-ft)
- Connecting rod bolts: approx. 54 Nm (40 lb-ft)
- Flywheel bolts: approx. 110 Nm (81 lb-ft)
- Crankshaft pulley bolt: approx. 155 Nm (114 lb-ft)
- Intake manifold bolts: approx. 22 Nm (16 lb-ft)
- Exhaust manifold: approx. 28 Nm (21 lb-ft)
- Spark plugs: approx. 18 Nm (13 lb-ft)
- Oil drain plug: approx. 34 Nm (25 lb-ft)
The Nissan L20 engine powered several
models, including:
- Nissan Cedric (130/230/330 series)
- Nissan Gloria
- Nissan Laurel C30/C130/C230
- Nissan Skyline (Japan-only trims)
- Nissan Fairlady Z (some early Japan-only 2.0L trims)
- Nissan Bluebird 2000GT (rare versions)
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