The Lotus V650 is a 2,174 cc, V6, single overhead camshaft (SOHC) petrol engine produced between 1980 and 1987. It featured a 60° V6 architecture with two valves per cylinder, chain-driven camshafts, and an iron block with aluminium heads. In standard form it delivered 130 PS (96 kW) at 5,200 rpm with 175 Nm of torque, providing smooth mid-range power suited to grand touring applications.
Fitted exclusively to the Lotus Éclat Series 3 and early Lotus Excel models, the V650 was engineered for refinement and drivability over outright performance. Emissions compliance was achieved through a single-barrel downdraft carburettor and positive crankcase ventilation, allowing compliance with UK national standards of the pre‑Euro era.
One documented concern is premature wear of the camshaft chain tensioner, which can lead to timing chain slap and eventual jump. This issue, highlighted in Lotus Engineering Service Bulletin LTB‑03/82, is attributed to marginal oil pressure at the tensioner feed during cold starts. From 1984, Lotus revised the oil gallery design and introduced a reinforced nylon tensioner shoe.
Production years 1980–1987 predate formal Euro emissions standards; compliance was based on national regulations (UK VCA Type Approval #VCA/EMS/V650L).
The Lotus V650 is a 2,174 cc V6 SOHC petrol engine engineered for grand touring coupes (1980–1987). It combines a pushrod-inspired valvetrain with a compact 60° V layout to deliver smooth torque and quiet operation. Designed before formal Euro standards, it met contemporary UK national emissions requirements through carburetion and crankcase ventilation.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 2,174 cc | |
| Fuel type | Petrol (Unleaded, min. 95 RON) | |
| Configuration | V6, SOHC, 12‑valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 81.0 mm × 70.3 mm | |
| Power output | 130 PS (96 kW) @ 5,200 rpm | |
| Torque | 175 Nm @ 3,500 rpm | |
| Fuel system | Single-barrel downdraft carburettor (Zenith-Stromberg) | |
| Emissions standard | Pre‑Euro (UK National Standards) | |
| Compression ratio | 8.8:1 | |
| Cooling system | Water‑cooled | |
| Turbocharger | None | |
| Timing system | Chain (front‑mounted, single-row) | |
| Oil type | SAE 10W‑40 (API SF/CC) | |
| Dry weight | 158 kg |
The SOHC V6 layout provides smooth torque ideal for relaxed cruising but requires vigilant timing chain maintenance. The original single-row chain and nylon tensioner are prone to wear below 60,000 km, especially with infrequent oil changes. Use of SAE 10W-40 meeting API SF/CC is essential to maintain oil pressure at the tensioner feed. Cold starts should be followed by a 30-second idle before driving to ensure cam chain lubrication. Post-1984 engines feature a revised oil gallery and reinforced tensioner per Lotus LTB‑03/82—pre-1984 units should be upgraded during rebuilds. Modern 95 RON unleaded fuel is acceptable with hardened valve seats.
Oil Specs: Requires SAE 10W-40 meeting API SF/CC (Lotus Workshop Manual 1982). Modern ACEA A3/B4 oils are acceptable substitutes.
Emissions: Pre-Euro era engine; compliance based on UK national standards (VCA Type Approval #VCA/EMS/V650L). No Euro certification applicable.
Power Ratings: Measured under DIN 70020 standards. Output reflects carburetted calibration for emissions (Lotus PT-Spec Sheet V650-Rev2).
Lotus Engineering Report LER-V650/80
Lotus Workshop Manual (1982 Edition)
Lotus Technical Bulletin LTB-03/82
VCA Type Approval Database (VCA/EMS/V650L)
The Lotus V650 was used across Lotus's Éclat and Excel platforms with longitudinal mounting and no external licensing. This engine received platform-specific adaptations—revised engine mounts for the Excel chassis and updated cooling ducts for the Series 3 Éclat—and from 1984 the Excel S adopted the revised oil gallery and tensioner, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine number stamped on the front face of the block near the timing cover (Lotus Workshop Manual 1982). Early units (1980–1983) have a black Zenith-Stromberg carburettor and cast-iron intake manifold; post-1984 versions use a silver carburettor and revised oil filler cap. The V650 is distinguished from the later 907/912 by its V6 configuration, single camshaft per bank, and absence of DOHC hardware. Head casting number ‘V650’ appears on the exhaust side of each cylinder head.
The V650's primary reliability risk is timing chain tensioner wear, with elevated incidence in vehicles subjected to frequent cold starts or extended oil intervals. Lotus internal data from 1983 indicated over 25% of pre-1984 engines required tensioner replacement before 70,000 km, while UK DVSA records show timing-related failures as a leading cause of non-start conditions in surviving examples. Infrequent use and marginal oil pressure make the LTB‑03/82 upgrade critical for long-term operation.
Analysis derived from Lotus technical bulletins (1980–1987) and UK DVSA failure statistics (2010–2023). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about LOTUS V650.
Comprehensive technical documentation and regulatory references
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EU emissions and type-approval regulations (e.g., CELEX:32007R0715, CELEX:32017R1151).
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UK vehicle approval processes, import rules, and MoT guidance.
DVLA: Engine Changes & MoT
Official guidance on engine swaps and inspection implications.
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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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