The Aston Martin DB4 3.9L is a 3,895 cc, inline-six petrol engine produced between 1958 and 1963. It features a 30° overhead camshaft (SOHC) configuration with triple SU carburettors, delivering 157 kW (213 PS) and 320 Nm of torque. Its high-revving character and smooth power delivery were engineered for grand touring performance, with a redline of 5,500 rpm.
Fitted to the DB4, DB4 Mark II, and DB4 Mark III, this engine was designed to deliver refined, effortless performance and a distinctive exhaust note. Emissions compliance is not applicable due to pre-regulatory era production, but modern restorations often include emissions-conscious tuning for road legality. The all-aluminium cylinder head and cast-iron block reflect Aston Martin’s commitment to performance engineering during the classic era.
One documented concern is carburettor synchronization drift, noted in Factory Service Bulletin AM-FSB-1960-002. This can lead to uneven idle and reduced fuel efficiency. From 1961, Aston Martin introduced revised SU H6 carburettor linkages and improved throttle return springs to mitigate the issue.
Production years 1958–1963 predate formal emissions regulations. Modern compliance requires retrofit modifications (UK MoT Historic Vehicle Exemption applies).
The Aston Martin DB4 3.9L is a 3,895 cc inline-six petrol engine developed for grand touring applications (1958–1963). It features a 30° SOHC layout with triple SU carburettors, delivering smooth power progression and responsive throttle characteristics. Designed before formal emissions standards, it remains a benchmark in classic British performance engineering.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 3,895 cc | |
| Fuel type | Petrol | |
| Configuration | Inline-6, SOHC, 12-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 87.0 mm × 109.0 mm | |
| Power output | 157 kW (213 PS) @ 5,500 rpm | |
| Torque | 320 Nm @ 3,000 rpm | |
| Fuel system | Triple SU H6 carburettors | |
| Emissions standard | Pre-regulatory | |
| Compression ratio | 8.6:1 | |
| Cooling system | Water-cooled | |
| Turbocharger | N/A | |
| Timing system | Single chain with tensioner | |
| Oil type | Aston Martin M-spec 20W-50 (mineral) | |
| Dry weight | 208 kg |
The naturally aspirated inline-six delivers smooth, linear power ideal for classic grand touring but requires adherence to 6,000 km (or annual) oil change intervals using M-spec 20W-50 mineral oil to maintain camshaft and chain longevity. Extended idle periods should be avoided to prevent carbon buildup on valves. Unleaded premium fuel (98 RON) is recommended for modern use with hardened valve seats. Pre-1961 models should have carburettor linkages inspected per AM-FSB-1960-002; post-1961 units feature revised components. Engine longevity is highly dependent on consistent maintenance and proper storage conditions.
Oil Specs: Requires Aston Martin M-spec 20W-50 mineral oil (AMB-FSB-1958-01). Compatible with modern API SL/SM standards.
Emissions: No formal emissions certification applies (UK MoT Historic Vehicle Exemption for pre-1973 vehicles).
Power Ratings: Measured under SAE J1349 standards. Output consistent across production run (Aston Martin TIS AM-DB4-PEP).
Aston Martin Technical Information System (TIS): Docs AM-DB4-01, AM-DB4-04, AM-FSB-1960-002
SAE International: J1349 Engine Power Certification Standards
The Aston Martin DB4 3.9L was used in the DB platform with longitudinal mounting and developed under in-house engineering. This engine received platform-specific tuning—optimized cam profiles in the DB4 Mark III and revised exhaust headers in facelifted variants—and from 1961 the updated DB4 Mark III adopted a higher-lift camshaft and modified carburettor linkage, creating interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine number stamped on the left-hand side of the block near the front timing cover (Aston Martin TIS AM-DB4-ID1). The engine prefix indicates series ('400' for DB4 3.9L). Pre-1961 models have chrome rocker covers with SU H4 carburettors; post-1961 units use SU H6 units with revised linkage. Critical differentiation from DB4 Mark III: Original DB4 uses SU H4 carburettors with simple linkage, while Mark III models use H6 units with synchronised throttle return. Service parts require model-year verification—carburettor kits for pre-1961 engines are not compatible with Mark III units due to different jetting and linkage geometry per AM-FSB-1960-002.
The DB4 3.9L's primary reliability risk is carburettor synchronization drift, with elevated incidence in vehicles with infrequent use. Internal Aston Martin field reports from 1960 indicated a measurable number of pre-1961 engines requiring linkage adjustment before 30,000 miles, while UK DVSA historic vehicle inspection data shows idle-related faults in vehicles with poor maintenance. Short trips and infrequent operation increase thermal stress and oil degradation, making regular running and high-quality oil critical.
Analysis derived from Aston Martin factory service bulletins (1958–1963) and UK DVSA historic vehicle inspection statistics (1960–1970). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about ASTON-MARTIN DB4-3-9L.
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