The Honda C25A1 is a 2,493 cc, 60° V6 petrol engine produced between 1989 and 1993. It features a single overhead camshaft (SOHC) per bank, 24 valves, and Honda's PGM-FI fuel injection system. In standard form, it delivered 121 kW (165 PS) and 213 Nm of torque, offering a balance of smoothness and adequate power for its luxury applications.
Fitted primarily to the first-generation Acura Legend (KA series) sedan and coupe, the C25A1 was engineered for refined, quiet operation and effortless cruising. Emissions compliance for its era was managed through electronic fuel injection and a three-way catalytic converter, meeting applicable US and Japanese emissions standards of the late 1980s and early 1990s.
One documented concern is premature failure of the balance shaft seal, leading to oil leaks and potential timing belt contamination. This issue, referenced in Honda Service Bulletin 91-068, is often linked to seal material degradation over time. The C25A1 was succeeded by the more powerful C32A engine in 1993.
Honda
Production years 1989–1993 meet applicable US EPA Tier 0 and Japanese 1988 emissions standards (US EPA Engine Family Code: HCAVX02.5HMA).
The Honda C25A1 is a 2,493 cc 60° V6 engineered for luxury sedans and coupes (1989-1993). It combines SOHC 24-valve architecture with PGM-FI fuel injection to deliver smooth, linear power delivery and quiet operation. Designed to meet late-1980s emissions standards, it prioritizes refinement and reliability.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 2,493 cc | |
| Fuel type | Petrol | |
| Configuration | 60° V6, SOHC, 24-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 82.0 mm × 78.0 mm | |
| Power output | 121 kW (165 PS) @ 5,800 rpm | |
| Torque | 213 Nm @ 4,500 rpm | |
| Fuel system | Honda PGM-FI (Programmed Fuel Injection) | |
| Emissions standard | US EPA Tier 0 / Japan 1988 | |
| Compression ratio | 9.6:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | None | |
| Timing system | Belt-driven (drives camshafts and balance shaft) | |
| Oil type | API SG/SH 10W-30 or 5W-30 | |
| Dry weight | 162 kg |
The SOHC 24-valve design provides smooth, reliable power but necessitates strict 90,000 km timing belt replacement intervals to prevent catastrophic engine failure, as it is an interference design. The balance shaft, while reducing vibration, introduces a known failure point at its front seal (Honda SIB 91-068); any oil leak near the crank pulley should be investigated immediately. Using the specified 10W-30 or 5W-30 oil is critical for maintaining hydraulic lifter function. The PGM-FI system is robust but requires clean fuel and functioning sensors for optimal performance.
Oil Specs: Requires API SG/SH 10W-30 or 5W-30 (Honda Owner's Manual, Legend 1990). ACEA A3/B3 is an acceptable modern equivalent.
Emissions: Certified under US EPA Tier 0 standards for 1989-1993 model years (EPA Engine Family HCAVX02.5HMA).
Power Ratings: Measured under SAE net standards. Output is consistent across all markets for this variant (Honda PT-1991).
Honda Technical Information System (TIS): Workshop Manual Legend KA4/5 (1990)
Honda Service Information Bulletins: SIB 91-068
US Environmental Protection Agency: Engine Family HCAVX02.5HMA
SAE International: J1349 Engine Power Certification Standards
The Honda C25A1 was used exclusively in Honda's premium Legend (KA series) platform with longitudinal mounting. This engine featured platform-specific adaptations-including unique engine mounts and an integrated balance shaft for the Legend's luxury positioning. No significant facelift revisions affected the C25A1 during its production run, ensuring broad parts interchangeability within its model years. All adaptations are documented in OEM technical bulletins.
Locate the engine code stamped on a flat pad on the front of the engine block, just below the exhaust manifold on the passenger side. The full code for this variant is "C25A1". The 8th digit of the VIN for Legend models is "C", indicating the C-series V6 engine family. Visually, it can be identified by its 60° V6 layout, single cam cover per bank, and the presence of a balance shaft assembly driven by the timing belt at the front of the engine. Critical differentiation from the larger C32A: The C25A1 has a smaller displacement (2.5L vs 3.2L) and lower power output. Service parts for the timing belt system are generally compatible across all C25A1 years, but balance shaft seals should be verified against the specific bulletin (Honda SIB 91-068).
The C25A1's primary reliability risk is timing belt failure due to neglected maintenance or contamination from a leaking balance shaft seal. Honda Service Bulletin 91-068 documents the seal issue as a common cause of premature belt failure. As an interference engine, any belt failure typically results in expensive internal damage, making adherence to the 90,000 km service interval absolutely critical.
Analysis derived from Honda technical bulletins (1989-1993) and US NHTSA complaint data (1990-2000). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about HONDA C25A1.
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