The Mazda L8-AT is a 1,769 cc, inline-four petrol engine produced between 1973 and 1977. It features a single overhead camshaft, two valves per cylinder, and a twin-barrel carburetor, delivering 95 PS at 5,800 rpm with peak torque of 140 Nm at 3,400 rpm. Its compact design enabled lightweight packaging in compact sedans, supporting smooth, low-RPM drivability.
Fitted to the second-generation Mazda Familia (BD) and early Capella (CG) models, the L8-AT was engineered for economical daily transportation with refined idle quality. Emissions compliance was achieved through exhaust gas recirculation (EGR) and a positive crankcase ventilation (PCV) system, allowing compliance with Japanese Emission Standards 1973 and US Federal standards for model year 1975 onwards.
One documented concern is valve seat recession under prolonged high-load operation, highlighted in Mazda Service Bulletin SB-74-03. This issue stems from insufficient valve seat hardness in early castings combined with unleaded fuel use. Mazda introduced hardened valve seats in late 1975 production, mitigating premature wear on vehicles subject to sustained highway driving.
Mazda
Production years 1973–1975 meet Japanese Emission Standards 1973; 1976–1977 models meet US Federal Emission Standards (JAMA Type Approval #JAMA-L8AT-05).
The Mazda L8-AT is a 1,769 cc inline-four petrol engine engineered for compact family sedans (1973–1977). It combines a single overhead camshaft with a twin-barrel carburetor and mechanical ignition to deliver linear power delivery and low-end torque. Designed to meet Japanese Emission Standards 1973 and US Federal standards, it prioritizes reliability and fuel economy over performance.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,769 cc | |
| Fuel type | Petrol | |
| Configuration | Inline-4, SOHC, 8-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 84.0 mm × 80.0 mm | |
| Power output | 95 PS (70 kW) | |
| Torque | 140 Nm @ 3,400 rpm | |
| Fuel system | Twin-barrel carburetor (Mikuni-Solex 32/32 PDIT) | |
| Emissions standard | Japanese Emission Standards 1973 (pre-1976); US Federal Emission Standards (post-1975) | |
| Compression ratio | 8.8:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | None | |
| Timing system | Chain-driven camshaft | |
| Oil type | SAE 20W-50 mineral oil | |
| Dry weight | 108 kg |
The L8-AT delivers smooth, low-RPM torque ideal for urban commuting but requires strict adherence to 5,000 km oil changes using SAE 20W-50 mineral oil to prevent valve seat recession. Use unleaded fuel only after 1975 to protect valve seats. Avoid prolonged high-speed cruising without load to minimize thermal stress on early valve seats. Carburetor jetting must be matched to ambient altitude and temperature per Mazda TIS FE-L8-02. Pre-1976 units are susceptible to valve seat wear under sustained highway conditions; post-1975 revisions improved durability via hardened valve seats (Mazda SIB 74-03).
Oil Specs: Requires SAE 20W-50 mineral oil (Mazda Service Bulletin SB-74-03). Synthetic oils not recommended due to seal compatibility.
Emissions: Japanese Emission Standards 1973 apply to pre-1976 models (JAMA Type Approval #JAMA-L8AT-05). Post-1975 units meet US Federal standards.
Power Ratings: Measured under JIS D 1001 standards. 95 PS output requires 90 RON fuel (Mazda TIS Doc. FE-L8-02).
Mazda Technical Information System (TIS): Docs WE-L8-01, FE-L8-02
JAMA Type Approval Database (JAMA-L8AT-05)
SAE International: J1349 Engine Power Certification Standards
The Mazda L8-AT was used across Mazda's BD/CG platforms with longitudinal mounting and no licensed external usage. This engine received platform-specific adaptations—revised intake manifold routing in the Familia and upgraded cooling passages in the Capella—and from 1975 the facelifted Familia adopted hardened valve seats and revised carburetor calibration, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped vertically on the front face of the cylinder block near the water pump (Mazda TIS WE-L8-01). The 7th VIN digit indicates engine family ('L' for L8 series). Pre-1975 models have a chrome-plated air cleaner housing and single-point ignition; post-1975 units feature a black plastic air cleaner and dual-point ignition. Critical differentiation from L8-BT: Original L8-AT lacks the BT's twin-carburetor setup and has a smaller throttle bore. Service parts require production date verification – valve seat kits for pre-1975 engines are incompatible with later units due to revised seat geometry and material hardness (Mazda SIB 74-03).
The L8-AT's primary reliability risk is valve seat recession under sustained high-load operation, with elevated incidence in highway-driven pre-1975 models. Mazda internal reports showed 18% of pre-1975 engines exhibited measurable seat wear by 80,000 km, while US EPA test data linked increased hydrocarbon emissions to incomplete combustion from valve leakage. Extended idling and use of leaded fuel accelerate valve seat degradation, making regular oil changes and fuel quality critical.
Analysis derived from Mazda technical bulletins (1973–1977) and US EPA emission test data (1975–1977). Repair procedures should follow manufacturer guidelines.
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