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 operatio…
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 | Refer to vehicle handbook / manufacturer specification | |
Dry weight | 162 kg |
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.
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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.
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The C25A1 is fundamentally a robust and smooth engine. Its long-term reliability is heavily dependent on preventative maintenance, specifically the 90,000 km timing belt and balance shaft seal replacement. If these are addressed, the engine can easily surpass 300,000 km with minimal issues.
The most common issues are oil leaks from the balance shaft seal, distributor O-ring, and valve cover gaskets. The critical failure point is the timing belt, which can fail catastrophically if not replaced on schedule or if contaminated by oil from a leaking seal.
The C25A1 was used exclusively in the first-generation Honda Legend, encompassing both the sedan (chassis code KA4) and coupe (KA5) variants, from model years 1989 through 1993 across all trim levels (Base, L, LS).
The C25A1 has limited tuning potential in its stock SOHC form. Basic modifications like a cold air intake and exhaust can yield minor gains. Significant power increases require internal engine work or forced induction, which is complex and costly for this engine design.
Fuel economy is moderate for its era and size. Expect figures around 10.5 L/100km (27 mpg UK) in the city and 7.5 L/100km (38 mpg UK) on the highway for the sedan. The heavier coupe will return slightly lower figures. Real-world consumption varies with driving style.
Yes. The C25A1 is definitively an interference engine. If the timing belt breaks or slips, the pistons will collide with the open valves, causing severe and expensive internal damage. This makes the timing belt service interval non-negotiable.
Honda originally specified API SG/SH 10W-30 or 5W-30. Modern equivalents meeting API SN or ACEA A3/B3 standards in 5W-30 or 10W-30 viscosity are suitable. Using a high-quality synthetic or semi-synthetic oil is recommended for optimal engine protection.
Comprehensive technical documentation and regulatory references
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EU emissions and type-approval regulations (e.g., CELEX:32007R0715, CELEX:32017R1151).
GOV.UK: Vehicle Approval & V5C
UK vehicle approval processes, import rules, and MoT guidance.
DVLA: Engine Changes & MoT
Official guidance on engine swaps and inspection implications.
Vehicle Certification Agency (VCA)
UK type-approval authority for automotive products.
Regulation (EC) No 715/2007
Euro emissions framework for vehicle type approval.
Commission Regulation (EU) 2017/1151
WLTP and RDE testing procedures for emissions certification.
GOV.UK: Vehicle Approval
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Type-approval guidance and documentation.
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