The Nissan H20 is a 1,998 cc, inline‑six naturally aspirated petrol engine produced between 1968 and 1986. It features an OHV, 12‑valve design with a single-barrel carburettor, prioritising rugged simplicity and low-cost maintenance. Peak output is rated at 66 kW (90 PS) and 152 Nm, making it suitable for commercial vehicles and basic passenger cars where durability and torque were paramount.
Fitted primarily to the Cedric 130, Patrol 60, and various forklifts/trucks, the H20 was engineered for dependable, low-revving workhorse duty. Its driving character is defined by ample low-end torque and mechanical robustness, ideal for hauling and off-road use. Emissions compliance relied on basic carburettor calibration, meeting pre-regulation standards for its long production period.
One documented concern is oil sludge accumulation in the rocker cover, which can restrict oil flow to the valve train. This issue, referenced in Nissan Technical Bulletin NTB78-012, is often attributed to extended oil change intervals or operation in dusty environments. Production ended in 1986 as Nissan transitioned to more efficient overhead-cam designs.
Production years 1968–1986 predate formal Euro emissions standards; certified under Japanese pre-1973 regulations (MLIT Japan Type Approval #JIS-D-0501).
The Nissan H20 is a 1,998 cc inline‑six naturally aspirated petrol engineered for commercial and passenger vehicles (1968-1986). It combines a simple OHV valvetrain with carburetted fuel delivery to deliver robust low‑end torque and exceptional mechanical longevity. Designed for pre-regulation markets, it prioritises serviceability over emissions performance.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,998 cc | |
| Fuel type | Petrol | |
| Configuration | Inline‑6, OHV, 12‑valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 73.0 mm × 79.5 mm | |
| Power output | 66 kW (90 PS) @ 4,400 rpm | |
| Torque | 152 Nm @ 2,400 rpm | |
| Fuel system | Single-barrel carburettor | |
| Emissions standard | Pre-regulation (Japan) | |
| Compression ratio | 8.2:1 | |
| Cooling system | Water‑cooled | |
| Turbocharger | None | |
| Timing system | Chain | |
| Oil type | API SF or equivalent (SAE 10W‑40) | |
| Dry weight | 185 kg |
The low compression ratio allows for reliable running on low-octane fuel but demands strict adherence to valve clearance checks at 20,000 km intervals. API SF specification oil is critical for protecting the OHV valvetrain and preventing sludge buildup. The timing chain is robust but should be inspected at major service intervals (100,000 km). Operation in dusty environments requires more frequent air filter changes to prevent carburettor contamination. Pre-heating via the choke is essential for smooth cold starts.
Oil Specs: Requires API SF (or equivalent) specification (Nissan SM-H20). SAE 10W-40 is recommended for all climates due to the engine's design.
Emissions: Pre-regulation certification applies to all 1968-1986 models (MLIT Type Approval #JIS-D-0501). No formal emissions standards were in effect.
Power Ratings: Measured under JIS D 1001 standards. Output is consistent across all applications (Nissan PT-1980).
Nissan Technical Information System: Docs SM-H20, NTB78-012
Japan Ministry of Land, Infrastructure, Transport and Tourism (MLIT)
MLIT Type Approval Database (JIS-D-0501)
Japanese Industrial Standards: JIS D 1001 Engine Power Certification
The Nissan H20 was used across Nissan's commercial and passenger platforms with longitudinal mounting. This engine received platform-specific adaptations-reinforced mounts in the Patrol for off-road use-and no significant facelift revisions occurred during its production run, ensuring broad parts interchangeability. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped on the flat machined pad on the left side of the cylinder block, near the rear freeze plug (Nissan SM-H20). The engine is visually identifiable by its inline-six configuration, OHV rocker cover, and front-mounted distributor. Critical differentiation from later L-series engines: H20 uses OHV (pushrod) design, while L-series are OHC. Service parts are generally compatible across all model years and applications, including industrial units.
The H20's primary reliability risk is oil sludge buildup in the rocker cover, with elevated incidence in dusty environments or with infrequent oil changes. Nissan internal service data indicated this was a leading cause of valve train wear for this model, while its simple mechanical design otherwise proved exceptionally durable. Neglecting oil maintenance makes adherence to the OEM service schedule critical.
Analysis derived from Nissan technical bulletins (1968-1986) and internal service reports. Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about NISSAN H20.
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