Nissan L26 Specifications
| Engine Model: Nissan L26 |
| Engine Type: 4-cycle inline 6-cylinder SOHC 12-valve liquid-cooled gasoline |
| Total Displacement: 156.5 cu.in (2.56 L) |
| Rated Engine Power: 140-150 Hp (104-112 kW) at 5600 rpm |
| Fuel System Type: Twin or single carburetors |
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The Nissan L26 is a 2.6-liter inline-six,
overhead-camshaft gasoline engine belonging to the iconic Nissan-Datsun
L-series family. Introduced in the early 1970s, the L26 served as the
powerplant for the Datsun 260Z (S30 chassis) and several Nissan sedans
in international markets. As the middle variant between the L24 and L28
engines, the L26 provides a well-balanced combination of torque,
mid-range drivability, and smoothness typical of inline-six powerplants.
The engine’s strong cast-iron block, aluminum OHC cylinder head, dual
carburetors, and durable timing chain system contributed to excellent
reliability and long service life.
The L26 was developed to increase displacement and torque compared with
the earlier L24, particularly to support larger and heavier vehicles
entering the global market. While producing slightly more torque than
the L24, the L26 maintains similar smoothness and responsiveness. The
L26 remains a favorite among Nissan enthusiasts today thanks to its
mechanical simplicity, robust construction, and suitability for
restoration. The engine responds well to traditional tuning methods,
retains excellent longevity even under heavy load, and offers
period-correct performance for classic Z-car restorations.
The Nissan L26 is a water-cooled, inline-six, four-stroke gasoline
engine with a total displacement of 2565 cc, or approximately 156.5
cubic inches. Bore is 83.0 mm (3.27 inches) and stroke is 79.0 mm (3.11
inches), resulting in a moderately oversquare configuration that favors
airflow, responsiveness, and higher-rpm breathing while maintaining good
low-end torque.
Compression ratio varies depending on region and factory carburetor
configuration but ranges from 8.3:1 to 8.8:1. Output varies as well, but
figures include 140-150 Hp (104-112 kW) at approximately 5200-5600 rpm,
and 150-160 lb-ft of torque (203-217 Nm) around 3600-4400 rpm. Idle
speed is usually specified at 700-800 rpm. The firing order is the
standard Nissan inline-six sequence: 1-5-3-6-2-4.
The L26 features a highly durable cast-iron block with thick cylinder
walls that allow numerous overbore rebuilds. The block design is
extremely rigid and able to withstand high thermal and mechanical loads.
This robustness is part of why classic Z-car engines are renowned for
their longevity.
The crankshaft is a forged steel six-throw unit supported by seven main
bearings. The seven-bearing layout offers excellent smoothness and
stability, crucial for high-rpm inline-six operation. Each connecting
rod is forged steel with generous bearing surfaces for long-term
durability. Aluminum alloy pistons use a conventional three-ring
arrangement - two compression rings and one oil-control ring. The piston
crown is designed to promote efficient combustion and stable torque
delivery.
The L26 uses an aluminum OHC cylinder head with a single camshaft
operating two valves per cylinder, totaling twelve valves. The head uses
wedge-shaped combustion chambers for efficient burn characteristics and
consistent flame propagation. The camshaft is driven by a durable
double-row steel timing chain. The chain tensioner is hydraulic and
automatically adjusted via engine oil pressure.
Valve sizes vary by application, but common
specifications include:
- Intake valve diameter: approximately 42 mm (1.65 in)
- Exhaust valve diameter: approximately 35 mm (1.38 in)
Valve lash is manually adjustable and must
be checked regularly. Cold clearances:
- Intake: 0.25 mm (0.010 in)
- Exhaust: 0.30 mm (0.012 in)
The L-series OHC valvetrain is simple, reliable, and service-friendly.
The L26 was produced in several carburetor configurations depending on
market and emissions regulations. The most iconic configuration uses two
Hitachi-SU (semi-downdraft) carburetors, which offer excellent
atomization and smooth throttle response when tuned properly. Later U.S.
emissions-era versions adopted modified carburetors and additional
vacuum and thermal controls, reducing performance but allowing
regulatory compliance.
Fuel delivery is provided by a mechanical camshaft-driven pump supplying
fuel at low pressure (2.5-4 psi). A paper-element inline fuel filter
protects the carburetors from contaminants.
Common carburetor system features:
- Idle mixture and idle speed adjustments
- Main and secondary jet circuits
- Choke mechanism (manual or automatic)
- Accelerator pump
- Vacuum-modulated components (later models)
- Anti-dieseling (fuel cut) solenoid on some versions
Ignition timing varies by model but typically is set around 8-12° BTDC
at idle, advancing mechanically and via vacuum advance.
The L26 uses a full-pressure lubrication system with a trochoid-type oil
pump. Oil is pumped through a full-flow replaceable filter and
distributed to the crankshaft bearings, connecting rod bearings,
camshaft journals, rocker arms, and timing chain assembly.
Oil capacity with filter is 4.5-5.0 liters (4.8-5.3 U.S. quarts).
Recommended oil viscosity depends on climate but standard ranges from
SAE 10W-30 to 20W-50 for classic engine operation.
Oil pressure:
- 3000 rpm: 350-450 kPa (50-65 psi)
- Idle: > 70 kPa (> 10 psi)
Cooling is handled by a belt-driven centrifugal water pump circulating
coolant through the block, cylinder head, heater core, and radiator.
Thermostat opening temperature is around 82°C (180°F), with full opening
near 95°C (203°F). Cooling system capacity averages 8.0-9.0 liters
(8.5-9.5 quarts).
The L26 cooling system includes:
- Cross-flow copper/brass or aluminum radiator
- Mechanical cooling fan (some models with viscous clutch)
- Bypass passages for warm-up control
- Temperature sender for dashboard gauge
| Intake and Exhaust Systems |
Induction on the L26 depends on carburetor configuration. Dual
carburetor engines use aluminum intake manifolds that distribute air
evenly to all cylinders. The design supports smooth mid-range torque and
responsive acceleration.
The exhaust system uses a cast-iron manifold with a six-into-two runner
design that balances flow distribution. Performance engines often use
tubular headers to improve exhaust scavenging and high-rpm power.
| Ignition and Electrical System |
Ignition is provided by a distributor mounted on the engine block.
Depending on production year:
- Early systems used breaker points and condenser
- Later systems used electronic ignition modules
The distributor includes:
- Centrifugal advance weights
- Vacuum advance diaphragm
Spark plug: NGK BP6ES or equivalent
Gap: approx. 0.8 mm (0.031 in)
Electrical output is handled by an alternator producing between 35 and
50 amperes depending on year.
Depending on market, the L26 may include:
- PCV (positive crankcase ventilation)
- EGR system (late models)
- EVAP charcoal canister
- Secondary air-injection pump (emission models)
- Anti-dieseling solenoid
- Thermal vacuum valves
- Length: 720-760 mm (28.3-29.9 in)
- Width: 520-540 mm (20.5-21.3 in)
- Height: 650-720 mm (25.6-28.3 in)
Dry weight: 190-215 kg (419-474 lb), depending on accessories.
Recommended maintenance intervals:
- Oil and filter: every 5000-8000 km (3000-5000 miles)
- Spark plugs: every 15,000-20,000 km
- Valve lash: every 20,000 km
- Fuel filter: every 20,000-30,000 km
- Air filter: every 20,000 km
- Coolant: every 40,000 km or 2 years
- Timing chain: inspect at high mileage
- Compression: healthy engines show 150-175 psi (1034-1206 kPa), <10%
variation
- Cylinder head bolts: 100 Nm (74 lb-ft)
- Main bearing caps: 85 Nm (63 lb-ft)
- Connecting rod bolts: 54 Nm (40 lb-ft)
- Flywheel bolts: 110 Nm (81 lb-ft)
- Crankshaft pulley bolt: 155 Nm (114 lb-ft)
- Intake manifold bolts: 22 Nm (16 lb-ft)
- Exhaust manifold nuts: 28 Nm (21 lb-ft)
- Spark plugs: 18 Nm (13 lb-ft)
- Oil drain plug: 34 Nm (25 lb-ft)
The L26 powered several important Nissan
models:
- 1974-1978 Datsun 260Z (S30)
- Nissan Cedric/Gloria (selected trims)
- Nissan Laurel (international variants)
- Nissan 230/330 series sedans
- Regional utility and commercial vehicles
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