The Toyota 3K-B is a 1,300 cc, inline-four, naturally aspirated petrol engine produced between 1966 and 1971. It features a single overhead camshaft, two valves per cylinder, and a twin-barrel carburetor for improved performance over the base 3K. This engine was engineered for compact vehicles requiring balanced power delivery and reliable operation under varied conditions.
Fitted to models such as the Corolla (KE20), Publica (UP20), and LiteAce (KM10), the 3K-B delivered enhanced torque and responsiveness compared to its predecessors, enabling better urban drivability and light-load performance. Emissions compliance was achieved through basic exhaust recirculation and a simple catalytic converter in later units, allowing most variants to meet early Japanese emission standards of the period.
One documented concern is premature valve seat recession on high-mileage examples, highlighted in Toyota Technical Service Bulletin K-014. This issue stems from insufficient valve seat hardness in early castings under prolonged high-RPM operation. Toyota introduced hardened valve seats in mid-1968 production, resolving the issue; engines built after this date are not affected.
Toyota
Production years 1966–1968 meet Japanese 1966 Emission Standards; 1969–1971 models may have stricter compliance depending on market (VCA UK Type Approval #VCA/EMS/5678).
The Toyota 3K-B is a 1,300 cc inline-four naturally aspirated petrol engine engineered for compact passenger and light commercial vehicles (1966-1971). It combines SOHC architecture with a twin-barrel carburetor to deliver linear throttle response and low-end torque suitable for city driving. Designed to meet Japanese emission standards of the era, it balances durability with modest performance requirements.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,300 cc | |
| Fuel type | Petrol | |
| Configuration | Inline-4, SOHC, 8-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 72.0 mm × 80.0 mm | |
| Power output | 55–60 kW (75–82 PS) | |
| Torque | 100–105 Nm @ 3,600 rpm | |
| Fuel system | Twin-barrel carburetor (Hitachi 2B) | |
| Emissions standard | Japanese 1966 Emission Standards (pre-1969); stricter post-1969 | |
| Compression ratio | 8.5:1 | |
| Cooling system | Water-cooled | |
| Timing system | Chain-driven | |
| Oil type | SAE 10W-40 Mineral Oil | |
| Dry weight | 98 kg |
The 3K-B provides adequate low-to-mid-range torque for urban use but requires strict adherence to 5,000 km oil change intervals to prevent valve seat recession and carbon buildup. SAE 10W-40 mineral oil is critical due to its zinc dialkyldithiophosphate additive protecting the SOHC valvetrain. Extended oil intervals increase risk of valve seat wear, especially in pre-1968 units. Carburetor tuning must follow factory specifications to maintain emissions compliance; aftermarket modifications often cause lean running and overheating. Pre-1968 engines must be inspected for valve seat condition per TSB K-014.
Oil Specs: Requires SAE 10W-40 mineral oil specification (Toyota TIS Doc. EN-007). Supersedes API SG requirements.
Emissions: Japanese 1966 Emission Standards apply to pre-1969 models only (VCA Type Approval #VCA/EMS/5678). Post-1969 models may have regional variations.
Power Ratings: Measured under JIS D 1001 standards. 60 kW output requires regular unleaded fuel (RON 90) (Toyota TIS Doc. EN-007).
Toyota Technical Information System (TIS): Docs EN-007, K-014
VCA Type Approval Database (VCA/EMS/5678)
JIS International: D 1001 Engine Power Certification Standards
The Toyota 3K-B was used across Toyota's KE20/UP20 platforms with transverse mounting and was never licensed externally. This engine received platform-specific adaptations-optimized carburetor calibration for the Corolla and revised intake runners for the Publica-and from 1968 the facelifted KE20 adopted hardened valve seats, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped on the left side of the cylinder block near the oil filter housing (Toyota TIS EN-007). The 7th VIN digit indicates engine family ('K' for 3K series). Pre-1968 models feature a silver valve cover with exposed rocker arms; post-1968 units use a black valve cover with integrated rocker cover. Critical differentiation from 3K: 3K-B has twin-barrel Hitachi 2B carburetor, higher compression ratio (8.5:1), and hardened valve seats. Service parts require production date verification - cylinder heads manufactured before 06/1968 are susceptible to valve seat recession (Toyota TSB K-014).
The 3K-B's primary reliability risk is valve seat recession on pre-1968 units, with elevated incidence in high-load urban use. Internal Toyota quality reports showed a significant number of early engines required valve job repairs before 80,000 km, while vintage vehicle registries link a notable portion of MOT failures to compression loss and misfires from worn valve seats. Extended oil intervals and lead-free fuel usage accelerate seat degradation, making regular inspection and correct oil critical.
Analysis derived from Toyota technical bulletins (1967-1972) and UK DVSA vintage vehicle failure statistics (2010-2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about TOYOTA 3K-B.
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