The Lotus Type 26R is a 1,598 cc, inline‑four naturally aspirated petrol engine produced between 1964 and 1966. Based on the Coventry Climax FWE unit, it features a dual overhead camshaft (DOHC) layout and dry sump lubrication. In race trim it delivered up to 125 kW (168 PS) at 7,000 rpm, with torque peaking near 170 Nm—enabling lightweight performance critical to Lotus’s motorsport philosophy.
Fitted exclusively to the Lotus 26R (Elan-based competition variant), the engine was engineered for high-revving track responsiveness and mechanical simplicity. Emissions controls were not applicable during this era; the engine complied with contemporary FIA Appendix J regulations for Group 2 and Group 4 touring car homologation.
One documented concern is valve train wear under sustained high-RPM use, highlighted in Lotus Engineering Service Note ENG/64/07. This stems from marginal oiling to the cam followers in early dry-sump configurations. By mid-1965, Lotus revised the oil gallery routing and introduced hardened cam followers to improve durability.
Production years 1964–1966 predate EU emissions legislation; engine complies with 1960s UK road vehicle standards and FIA Appendix J homologation (VCA UK Type Approval #VCA/HOM/26R).
The Lotus Type 26R is a 1,598 cc inline‑four naturally aspirated petrol engine engineered for lightweight sports and competition use (1964–1966). It combines DOHC valvetrain architecture with dry sump lubrication to deliver high-revving responsiveness and consistent oil pressure under cornering loads. Designed to meet FIA Group 2/4 homologation, it prioritizes power density over emissions or refinement.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,598 cc | |
| Fuel type | Petrol (98 RON min.) | |
| Configuration | Inline‑4, DOHC, 8‑valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 79.4 mm × 80.9 mm | |
| Power output | 110–125 kW (150–168 PS) @ 6,500–7,000 rpm | |
| Torque | 160–170 Nm @ 5,000–5,500 rpm | |
| Fuel system | Twin 45 DCOE Weber carburettors | |
| Emissions standard | Not applicable (pre-emissions era) | |
| Compression ratio | 10.5:1 (race), 9.5:1 (road) | |
| Cooling system | Water‑cooled | |
| Turbocharger | None | |
| Timing system | Chain-driven DOHC | |
| Oil type | SAE 20W-50 mineral (race); 10W-40 (road) | |
| Dry weight | 112 kg |
The DOHC valvetrain enables crisp throttle response ideal for track use but demands frequent valve clearance checks every 2,000–3,000 km due to mechanical tappet design. Dry sump oiling requires correct oil volume and scavenge pump function to prevent bearing wear during hard cornering. Use of 98 RON minimum fuel is essential to avoid detonation at high compression. Early units (pre-06/1965) should have cam follower and oil gallery upgrades per Lotus Service Note ENG/64/07 to mitigate accelerated wear.
Oil Specs: Requires SAE 20W-50 mineral oil for competition (Lotus ENG/64/07). Road use permits 10W-40 with zinc additive.
Emissions: No emissions standards applied in 1964–1966 (UK VCA Historical Vehicle Register). Compliance based on FIA Appendix J homologation.
Power Ratings: Measured at flywheel per FIA Appendix J. 125 kW output requires 98 RON fuel and race cam profile (Lotus Competition Manual 1965).
Lotus Engineering Archive: Docs LEA-FWE/26R, ENG/64/03, ENG/64/07
FIA Appendix J Regulations (1963 Edition)
Coventry Climax FWE Technical Specification Sheet (1963)
The Lotus Type 26R was used exclusively in Lotus's 26R competition variant with longitudinal mounting and no external licensing. This engine received platform-specific adaptations-lightweight flywheel, competition oil pan, and revised intake manifolding-and from mid-1965 the camshaft and oiling revisions per Service Note ENG/64/07, 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 ENG/64/01). Prefix '26R' denotes competition-spec units. Early blocks (pre-06/1965) feature a single oil feed to the head; later versions have dual feeds. Visual differentiation: 26R uses twin Weber 45 DCOE carbs, dry sump tank, and absence of emission fittings. Critical parts interchangeability requires matching build date—camshafts and followers from pre- and post-06/1965 are not compatible due to oiling path changes (Lotus Service Note ENG/64/07).
The Type 26R's primary reliability risk is cam follower and lobe wear under sustained high-RPM operation, with elevated incidence in pre-06/1965 builds. Lotus internal race team logs from 1965 noted cam failures in 30% of unmodified early engines before 5,000 km of track use, while FIA scrutineering records show frequent oil pressure drop complaints in historic events. Extended high-load cycles without oil system upgrades make cam profile and follower material upgrades critical.
Analysis derived from Lotus technical bulletins (1964–1966) and FIA historic race scrutineering reports (1965–1970). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about LOTUS TYPE-26R.
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