page_title: Bentley Mark VI
section_title: Engine
hierarchical_section_title: Bentley Mark VI / Engine
caption_attribution_description: Working on the engine of 1950 Bentley MK VI.
context_page_description: The Bentley Mark VI is an automobile from Bentley which was produced from 1946 to 1952.
  The Mark VI 4-door standard steel sports saloon was the first post-war luxury car from Bentley. Announced in May 1946 and produced from 1946 to 1952 it was also both the first car from Rolls-Royce with all-steel coachwork and the first complete car assembled and finished at their factory. These very expensive cars were a genuine success; long-term, their weakness lay in the inferior steels forced on them by government's post-war controls. Chassis continued to be supplied to independent coachbuilders. Four-door Saloon, two-door saloon and drophead coupe models with bodies by external companies were listed by Bentley along with the Bentley-bodied saloon.
  This first Bentley factory finished car was given the name Bentley Mark VI standard steel sports saloon. This shorter wheelbase chassis and engine was a variant of the Rolls-Royce Silver Wraith of 1946 and, with the same standard steel body, became the cautiously introduced Silver Dawn of 1949.
context_section_description: The Mark VI ​4 ¹⁄₄-litre used an F-head straight-6 engine 4.3 L (4,257 cc/259 cu in) in size.   The manufacturer refused to disclose a horse power value for the car (other than Tax Horsepower of 29.4 hp according to the old RAC formula) but an Autocar Magazine road test reproduced in 1950 reported that top gear provided "flexibility down to 6 mph (10 km/h)" and the ability to "climb a hill of 1 in 9 maximum gradient, complicated by bends", all of which supported the manufacturer's contention that power, along with low speed torque, were adequate.
  . 
  In 1951, a ​4 ¹⁄₂-litre, 4.6 L (4,566 cc/278 cu in) version of the engine was introduced. The increase in displacement was accomplished by increasing the bore from 3 1/2 inch to 3 5/8 inch. The later version is sometimes casually referred to as the "big bore" engine, the earlier version as the "small bore" version. The 4 1/2 L version of the engine is as well equipped with a Vokes 30 (later: Vokes 62) full flow oil filter (some earlier 4 1/4 L cars have since been modified to a full flow filtration system).
  Carburation in RHD (right hand drive) cars were two horizontal constant-vacuum SU carburetors (type H4 up to B81HP, type H6 from B83 HP on). LHD (left hand drive) cars had a single dual downdraught Stromberg carburetor type AAV26M and a different inlet manifold as fitted in the Rolls Royce Silver Dawn and Silver Wraith.
  A four-speed syncromesh manual transmission was fitted in all Bentley MK VI with the change lever to the right of the driver on RHD cars and on the column on LHD versions.  
  ​4 ¹⁄₄-litre cars had chassis numbers from B 1 AJ through B 400 LJ, with the final two letters indicating the series in which it was built. The "big bore" cars serial numbers begin with B 1 MB (although B 2 MD was the first big bore Mark VI built) and ended with B 300 PV (although B 301 PU was the last one built). Each alphabetic series only contained either even or odd numbers, and 13 was always skipped for the odd-numbered sequences.
  The 4.3 L (260 cu in) was referred to as the ​4 ¹⁄₄ L and can be quickly identified from its single exhaust in RHD cars. The 4.6 L (280 cu in) is known as the ​4 ¹⁄₂ L and features a twin exhaust in RHD cars. In LHD cars the (much less restrictive) twin exhaust system was only fitted with the introduction of the R-type.  
  In addition for "standard steel" Mark VI saloons the single hinged ventilation flap centrally mounted on the top of the bonnet, directly ahead of the windscreen was replaced, on later cars, with two hinged ventilation flaps, mounted at or slightly below knee height, one on each side of the bonnet, ahead of the front doors.  The oil filler cap is another way to identify engine type; a plastic cap is typical of a "small bore" engine, a metal cap of a "large bore" engine.
caption: a 4¼ Litre engine
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