Bentley MKV1 Engine Rebuild - 24/02/2010

The planned day has finally arrived, when my lovely old Bentley MKV1 has had to surcome to her probably second engine overhaul. Amazingly with the oil smoke letting by after a run, the grand old lady “Catherine” (named after Catherine Deneuve the French film star), even with a worn engine still cruised at 70 mph. Catherine has never had a “fail to proceed” as Rolls Royce like to term a breakdown since she came back to life after a long rest seven years ago. What can we see and learn from the archaeology of this B60 4.25 engine? The Bricrome liners are still totally in tact as installed in 1949, the wear pattern is quite even and would still fall within RR recommended tolerances, however the main wear which is very close to tolerance is number 4 piston. The cam is worn but still has life in it yet although a new one will be fitted. The wear on the pistons is even, several of the piston rings were broken. The bearing are showing the base metal.

At some time this engine had an overhaul, looking at how the work was completed not by an RR engineer as the lock tab washers were incorrectly inserted andseveral signs of lack of attention to detail give the clues away, as the engine archaeology team dig deeper they estimate late 1950’s/early 1960’s overhaul.One/two of the con rods are showing signs of an oil blockage.

What is the next step?

We have gone to great lengths to source all the RR genuine parts over many years, the job now is to bring those parts together.

The plan is that the engine block will now have her full length liners inserted. Whilst this work is undertaken, the task has begun of cleaning the underneath between the front floor pan and the top of the chassis, the oil and grease has preserved the paint well, although the job of digging the mix of road debris, grease and oil out of the box section is very time consuming and dirty. We want to preserve as much of the original paint as possible only touching in areas where needed, blending in the black paint to keep this excellent chassis in original condition.

We are of the firm view of “Do it once do it right” the aim of the engine rebuild is as follows:
• To original specification 4.25 Litre ( matching numbers)
• To use original RR new /old stock
• To assemble the engine to the highest standards possible

At Pride and Joy we get tremendous enjoyment at seeing original MKV1’s with lots of patina being sympathetically restored to preserve what is “Probably the best car in the World”

Please watch our website for the next instalment on this exciting engine rebuild

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Cars On Test - 1950 Bentley MKV1 Donington Special

Every so often an opportunity arises to drive a car that stands out from the crowd, certainly all Bentley MKV1 Special are different as each car is tailor-made to the builder’s specification, however, due to either the degree of engineering that went into making the car or the effort needed to combine the best in everything post war Bentley, makes some Bentley Specials more special than others and this is one such very special car. So, what is a MKV1 Special? The post war range of Rolls Royce cars marketed as the Bentley MKV1 started production in 1946, these were highly prized and expensive cars in a car starved post war Britain, when you needed authorisation to purchase a new car until 1953. The first cars had a very efficient 6 cylinder 4.25 litre engine, later increased to 4.5 litres in 1951, a robust engine with overhead inlet and side exhaust valves, silky smooth four speed gearbox and a luxury interior with a body made by Pressed Steel Fisher. All this sat on an excellent chassis, up to 7” thick in places that proved to give road holding capabilities second to none.

Unfortunately (or fortunately for the MKV1 Special builder) the MKV1 bodies started to rust, very badly at first as the early post war metal was prone to deterioration. The second hand cars soon began to depreciate quickly and in some cases became beyond economical repair.

This opened up Bentley ownership for lots of enthusiasts in the 1960’s, many of these worked in engineering who dreamt of owning a vintage Bentley (pre 1931 when WO Bentley was manufacturing the cars that bore his name). They purchased a car usually quite cheaply, the body usually beyond repair.What these early MKV1 Special builders wanted was a good chassis and an engine that was a “goer” using the well tested Rolls Royce servo braking system to stop the car.

In the late 1970’s I personally remember when Bentley Driver’s Club meetings were held in a proper pub “wot” sold ale, we met after we had our dinner at home for a “noggin and a natter” it did not matter what car you had (if any as long as you were interested) almost everyone did their own work, talk at the bar could be around a Vintage “C “gearbox, a Parkward Derby’s coachwork or……. Building a Special, other members offered advice and help. A trip outside to the pub car park was almost mandatory to view work in progress. The idea was to build a body to make the car look like a Vintage Bentley, there were several companies that made kit bodies such as Harry Rose. Shortening the chassis was the debate, by how much and where or if to do this at all. This became the entry level car into Bentley Driver’s Club, and as time went on so the MKV1 Special was a badge of a good engineer, more members wanted the ease of maintaining a Special and the sheer exhilaration of driving a fast sports car.

Enter the professional MKV1 Special builders, in the early 1970’s restorers saw the opportunity to both demonstrate their skills , make profit and compete on both road and track as to who could put the best MKV1 Special into production.

The test report that follows is a professionally built Bentley MKV1Donington Special, the named Donington after the race track and this car is number 15 of 16 cars built by John Guppy and John Johnard at their engineering workshop in Dorset in 1979. The Donington is even more special as all 16 cars gained the approval of Bentley Motors. This car started life as a Special with a 4.25 litre engine, and then in 1992 things really took a change for the better when number 15 saw a dramatic enhancement. Out came the 4.25 litre and in its place a 5.1 litre straight six Bentley S1 engine tuned to 9.1 compression ratio with triple 2 “HD8 SU carburettors all tuned by Bentley ace Alan Padgett and John Guppy to produce over 250 BHP. To keep this power in place a Jaguar E Type 2.88:1 limited slip differential was fitted. And what is the Top speed you may ask? estimated at 140mph.

A monster, yes! it can be but also an amazingly practical car which I found out on my test drive on a cold February morning.

The current keeper of number 15 has put both a lot of time and money into upgrading both the comfort and the practical side of making this car a very usable special, and as I undertook my test route I began to appreciate how this additional spend was well worth the effort .

The conditions were cold to say the least but the sun was shinning all good for an open car, as I turned the key using a little choke the big engine instantly fired into life then settled to a burble through the specially designed and engineered exhaust system. The engine always started easily on test showing no signs of temperament as some MKV1 Specials have been know to.

As I strap myself into the full harness and acquaint myself with the splendid instrument layout, a Moto-Lita steering wheel, the Bentley speedo and original quarter section instrument dial to the Stack Chronometric tachometer. The fuel gauge is a marine type and with the light switches all easy to find in this weather, in gloved hands. A central handbrake and unusual for a MKV1 special a central gear change, tall easy to hand in true racing style with such details as a gate lock for reverse. I make myself comfortable in the cockpit with the view of the beautiful light walnut dash top with magnolia leather adjustable seats. The practical aspect of number 15 shows through with a full fire extinguisher system operated by the pull of a red lever if ever needed on the transmission tunnel. Further enhancements include a twin stainless steel fuel tank which is explosion proof; an up rated clutch and cooling system.

As I pull away using first gear I get the feel for the light clutch and start to experience the car warming up, the gearbox oil still cold as I “burble” through the leafy suburb with a cheery wave from the Postman and thumbs up from two boys on bicycles. I navigate with ease through the small shopping centre to the open road with a 40 mph speed limit which gives the engine time to warm to the 85 degrees constant temperature it is famous for. Around a double roundabout felt surefooted, power on as I descend the slip road to the fast dual carriage way, then I realised what the owner had said was true “sounds like a Spitfire on low pass when you press on” a Melin indeed which is where the heritage of these engine stems from, built in the same Crewe factory in Cheshire England. The 2” specially designed exhaust system not only sounds good but has practical properties in that the multibranch exhaust system takes heat away from the engine bay and gives added horsepower. Number 15 was now well into operating temperature, the cockpit was warm and cosy as I cruised along listening to the exhaust note in the winter sunshine.

This car will cruise effortlessly at speed far greater than that achieved by most MKV1 Specials; its acceleration is astonishing with good road holding, and its brakes smooth, progressive and powerful with Jaguar discs at the front and Bentley drum brakes at the rear For practical purposes, there is a very professionally made motorcycle pannier system which fits to the chassis with tailor- made suit cases for the stainless steel luggage rack. My lasting impressions are that for all number 15’s performance it can remain a refined car, a testimony to the Bentley marque, I really do want to drive this car for more miles before handing it back to the proud owner.