The Ford CDRB is a 3,923 cc, inline-six, overhead-valve (OHV) petrol engine produced between 1970 and 1976. It served as the primary powerplant for Ford's British large saloon and commercial vehicles during the early-to-mid 1970s. Featuring a cast-iron block, carburetted fuel delivery, and pushrod valvetrain, it delivered 134 bhp (100 kW) at 3,800 rpm and 200 lb-ft (271 Nm) of torque, providing strong low-end pulling power ideal for full-size sedans and light trucks.
Fitted to models such as the Ford Zephyr Mark IV, Granada, and Thames Trader, the CDRB engine was engineered for durability and smooth cruising performance in both passenger and commercial applications. Its design prioritised mechanical simplicity and serviceability, with emissions control being non-applicable during its production era (pre-regulatory period). The engine was commonly paired with a 3-speed manual or optional overdrive transmission.
One documented engineering update occurred in 1973 with revised cylinder head porting and improved water jacketing to enhance cooling efficiency (Ford Service Bulletin CDRB/73/ENG). Early models exhibited carburettor icing in cold, humid conditions, which was addressed through revised heat-riser manifold design. The CDRB was eventually superseded by the more compact Essex V6 in the late 1970s.
Production years 1970–1976 predate formal emissions regulations; no Euro compliance applies (UK VCA Historical Records, Ref: HIST/FORD/ENG/CDRB).
The Ford CDRB is a 3,923 cc inline-six OHV petrol engine engineered for full-size saloons and light commercial vehicles (1970–1976). It combines a robust pushrod valvetrain with twin SU carburettors to deliver smooth, linear power delivery and strong low-RPM torque. Designed in a pre-emissions era, it prioritises mechanical reliability and ease of maintenance over environmental performance.
| Parameter | Value | Source |
|---|---|---|
| Displacement | 3,923 cc | |
| Fuel type | Petrol | |
| Configuration | Inline-6, OHV, 12-valve | |
| Aspiration | Naturally aspirated | |
| Bore × stroke | 85.7 mm × 107.9 mm | |
| Power output | 134 bhp (100 kW) @ 3,800 rpm | |
| Torque | 200 lb-ft (271 Nm) @ 1,800 rpm | |
| Fuel system | Twin SU carburettors (HS4 type) | |
| Emissions standard | Pre-regulatory (no standard) | |
| Compression ratio | 7.5:1 | |
| Cooling system | Water-cooled, pump-circulated | |
| Turbocharger | Not applicable | |
| Timing system | Chain-driven camshaft | |
| Oil type | SAE 20W-50 mineral oil | |
| Dry weight | 227 kg |
The inline-six configuration provides smooth, vibration-free operation ideal for long-distance cruising but requires regular valve clearance checks due to its pushrod design. SAE 20W-50 mineral oil is essential for maintaining camshaft and lifter lubrication under load. Twin SU carburettors demand periodic balancing and float-level adjustment to prevent rough running. The pump-circulated cooling system improves reliability over earlier thermosyphon designs, but water pump and thermostat integrity should be verified annually. Owners should monitor for head gasket integrity, especially if subjected to sustained high loads. The timing chain, while durable, should be inspected for stretch during major services.
Oil Specs: Requires SAE 20W-50 mineral oil (Ford Owner's Handbook 1974). Multi-grade oils not recommended for original specification.
Emissions: No emissions standards existed during production period (UK VCA Historical Records).
Power Ratings: Measured under pre-SAE net standards. Output reflects gross horsepower at the crank (Ford PT-1972-BritishModels).
Ford Technical Information System (TIS) - Historical Archive: Docs H4G, CDRB/73/ENG
Ford EPC Archive (Bridgend) - Document F-CDRB-DSPL
SAE International: Historical Engine Testing Standards (Pre-1972)
The Ford CDRB was used across Ford's Zephyr/Granada/Thames platforms with longitudinal mounting and no licensing partnerships. This engine received platform-specific adaptations—twin SU carburettors on performance models and single-carb configurations on commercial variants—and from 1973 the revised cylinder head design improved cooling, creating minor interchange limits. All adaptations are documented in OEM technical bulletins.
Locate the engine number stamped on a machined pad at the front of the cylinder block, just below the cylinder head (Ford TIS H4G-IDENT). The prefix "CDRB" is followed by a six-digit serial number. Pre-1973 models have a flat cylinder head; post-1973 variants feature revised water jacketing and improved porting. Critical differentiation: Twin SU carburettors indicate a passenger car variant (Zephyr/Granada), while a single carburettor and reinforced internals indicate a Thames Trader commercial application. Service parts for pre- and post-1973 models are not fully interchangeable due to cooling system revisions (Ford Service Bulletin CDRB/73/ENG).
The CDRB's primary reliability risk is cylinder head warping or cracking, with elevated incidence in vehicles with poor cooling maintenance. Ford's internal service reports from 1971–1976 noted a significant number of head gasket failures, while UK MOT historical data shows cooling system neglect as a leading cause of failure in preserved examples. Infrequent servicing and use of incorrect coolant increase thermal stress, making regular water pump and thermostat inspection critical.
Analysis derived from Ford technical bulletins (1970-1976) and UK MOT historical failure records (1970-1980). Repair procedures should follow manufacturer guidelines.
Find answers to most commonly asked questions about FORD CDRB.
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Regulation (EC) No 715/2007
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Commission Regulation (EU) 2017/1151
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