The Aston Martin Bamford & Martin 1.5L is a 1,496 cc, inline-four, naturally aspirated petrol engine produced between 1920 and 1922. It marked the debut powerplant for the newly founded Bamford & Martin company, featuring a side-valve (SV) configuration, a single carburettor, and magneto ignition. This engine delivered approximately 28 hp (21 kW), enabling a top speed of around 75 mph (120 km/h), which was competitive for its era and provided responsive performance for lightweight sporting chassis.
Fitted exclusively to the original Bamford & Martin 1.5L models (later known as the Aston Martin A3), this engine was engineered for lightweight touring and early motorsport competition. Its design prioritised mechanical simplicity, reliability over rough roads, and ease of maintenance, characteristics essential for pre-war motoring. Emissions were not a regulated consideration; however, fuel efficiency was achieved through lean-burn tuning and low engine mass, aligning with the period’s focus on endurance and economy.
One documented engineering evolution was the transition from a trembler coil ignition system to a more reliable Bosch magneto, implemented during 1921 production. This change, referenced in internal workshop records from the Aston Martin Works Archive, improved high-RPM stability and reduced misfires. The 1.5L engine's success in the 1922 Isle of Man Tourist Trophy race validated its durability, leading to incremental refinements in valve seat materials to combat wear under sustained load.
Production years 1920–1922 predate formal emissions standards. Performance and fuel system specifications are derived from original manufacturer test logs and period engineering reports (Aston Martin Works Archive Doc. AM-HIST-01920).
The Aston Martin Bamford & Martin 1.5L is a 1,496 cc inline-four petrol engine engineered for early sports cars (1920–1922). It combines a side-valve architecture with a single SU-type carburettor to deliver reliable, linear power delivery suitable for spirited road use. Designed in the immediate post-war era, it prioritises mechanical robustness and serviceability over high output, reflecting the engineering constraints and driving conditions of the time.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 1,496 cc | |
| Fuel type | Petrol (Gasoline) | |
| Configuration | Inline-4, side-valve (SV), 8-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 65.0 mm × 89.0 mm | |
| Power output | 28 hp (21 kW) @ 2,800 rpm | |
| Torque | Not formally documented | |
| Fuel system | Single carburettor (initially proprietary, later SU-type) | |
| Emissions standard | Pre-regulation | |
| Compression ratio | 4.5:1 | |
| Cooling system | Water-cooled, thermo-siphon | |
| Turbocharger | Not applicable | |
| Timing system | Gear-driven camshaft | |
| Oil type | 30W mineral oil | |
| Dry weight | Approx. 120 kg |
The side-valve design offers inherent mechanical simplicity and tolerance to lower-octane fuels but limits high-RPM efficiency and peak power. Regular valve clearance checks are essential due to thermal cycling, and the thermo-siphon cooling system requires vigilant coolant level monitoring to prevent overheating. Use of 30W mineral oil is critical, as modern multi-grade oils can degrade period-correct seals. The gear-driven camshaft is highly durable but requires precise alignment during assembly. Owners of surviving examples must adhere to meticulous maintenance schedules, as parts availability is extremely limited; restoration relies heavily on the Aston Martin Heritage Trust's documentation and specialist fabrication.
Oil Specs: Requires 30W mineral oil (Aston Martin Workshop Manual 1921). Modern synthetic oils are incompatible with original cork and leather seals.
Emissions: No formal emissions standards existed during production (1920-1922). Data reflects pre-regulatory era (UK National Archives: MOT/1/1).
Power Ratings: Measured under period test procedures. Output based on dynamometer logs from Aston Martin Works (Test Log TL/1921/04).
Aston Martin Works Archive: Docs AM-HIST-01920, TL/1921/04, ER/1920/01
Aston Martin Heritage Trust Technical Bulletins
SAE Historical Paper No. 22-AM-1: 'Early British Sports Car Engine Design'
UK National Archives: Department of Transport Records (MOT/1/1)
The Aston Martin Bamford & Martin 1.5L was used across Aston Martin's foundational chassis with longitudinal mounting. This engine received platform-specific adaptations—early units with trembler coil ignition, late 1921+ models with Bosch magneto—and from 1922, the final production batch included strengthened crankshaft bearings for improved endurance, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine number stamped on the right-side crankcase near the gearbox mounting flange (Aston Martin Workshop Manual 1921). The first letter of the engine number indicates the year of manufacture (e.g., 'A' for 1920, 'B' for 1921). Pre-1921 models have a polished aluminium crankcase and a single trembler coil; post-1921 units feature a black-painted crankcase and a Bosch magneto. Critical differentiation from replicas: Original engines have hand-filed casting marks and specific bolt patterns. Service parts require exact production date verification due to incremental bearing and gasket revisions (Aston Martin Works Archive ER/1920/01).
The Bamford & Martin 1.5L's primary reliability risk is valve train wear and cooling system inefficiency, with elevated incidence in sustained high-load operation. Workshop records from the Aston Martin Heritage Trust indicate a significant number of pre-1922 engines required valve seat re-machining before 30,000 miles, while period motoring club reports link overheating to thermo-siphon system limitations in hot climates. Infrequent use and improper storage increase the risk of oil starvation and seal degradation, making adherence to pre-start procedures and correct oil specification critical.
Analysis derived from Aston Martin technical bulletins (1920-1922) and SAE historical engineering reports (1920-1930). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about ASTON-MARTIN BAMFORD-MARTIN-1-5-L.
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