Ferguson Prototype Flat Four Engine

Ferguson Prototype Flat Four Engine, Mike Thorne and Peter Smith:

Ferguson prototype Flat Four engine, designed to power the R5 Estate Car, developed and produced by Harry Ferguson Research Ltd (HFR).

This story started in 2012 when I received, out of the blue, a phone call from a gentleman based in Herefordshire, asking me if I would be interested in buying two prototype Ferguson car engines. One was an overhead valve unit, developed to power the R4 Ferguson car, while the other, the subject of this article, is an overhead cam engine, with toothed belts driving each camshaft. Yes, of course I was, but his asking price was far beyond my means and although he seemed very keen that they should come to the Coldridge Collection, I had to say sorry, I cannot afford to pay your asking price, and left it at that.

Well about ten days later he phoned me again with the suggestion that I may have a tractor that I would be prepared to swap for the two engines. My immediate response was yes, I have a MF165, fitted with a four wheel traction conversion in a rough, unrestored state, apart from the engine which was running quite well, all the sheet metal work was rusted out, but I had been able to buy some genuine replacement items second hand, so they were included in the swap. He was very happy with all this and a few days later he arrived with his 7.5ton 100TY with the two engines and a couple of boxed of various gaskets suitable for them. So we off loaded the engines and he drove the MF165 onto his lorry, strapped it down and set off back to Hereford.

The rusty and decaying engine as it arrived at Mike Thorne’s Coldridge collection.

I kept these engines in dry storage; they were viewed from time to time by interested visitors. One was a gentleman who had worked for HFR and he had been involved with the R5 project. It was he who told me that a batch of seven engines had been developed and built up, mine carries a commission plate marked P94/4 (project 94 number 4). He went on to tell me that on one, they had cut a piece out of the left hand rocker cover so that oil flow could be monitored, the cut was fitted with a perspex window. My reply was ‘that is this engine’!

Over time I have made a point of collecting any technical data relating to either of these engines. So far most of what I have been able to collect relates to the R5 engine, details of the earlier units seem to be more elusive. It is perhaps worth quoting here from one of these documents Automotive Engineer – March 1966 ‘A compact high performance 2232cc four cylinder horizontally opposed unit’ and a further quote ‘an engineer’s engine’. This power unit was designed by HFR chief engineer Claud Hill, an ex. Aston Martin designer. It was a very much developed follow on from the earlier OHV (push rods) that were installed in the Ferguson R4 car. Perhaps it should be mentioned here that Harry Ferguson Research was headed up at this time by Tony Sheldon, HF’s son-in-law, who took over following Harry Fergusons death in October 1960. Another aside is at one point in the development of the R4, the engineers were keen to road test it out, but their engine was not ready, so they decided to install a Jowet Javelin flat four OHV unit of 1.5 litres; by the way, the engine and the car were designed by their engineer, Gerald Palmer.

The specification of the R5 engine P94/4 is as follows:- Bore 95mm, stroke 78mm swept volume 2212cc, compression ratio 9:1, sump capacity 10pts of SAE 10/40. Its alternator is driven by a micro vee belt.

The first set of performance figures are taken from the Automotive Engineer dated March 1965 and are as follows: – max power output 125bhp at 5400rpm, max torque 131Ib/ft at 2500rpm, firing order 1,4,2,3. The second set of figures are taken from the Motor Magazines road test, dated August 1966 of the same engine i.e. fitted with two SU HD6 carburettors, max power 116bhp at 5400rpm, max torque 1281b/ft at 3500rpm.

The next part of this story started in the Summer of 2018 when Club members Julie Browning and Peter Smith visited the Coldridge Collection and Peter being a most competent motor engineer offered to rebuild this with his friend Robert McColl, needless to say I was delighted with this offer so the engine was loaded into their vehicle and they headed off back up to Cheshire.

Over now, to Peter Smith and Robert McColl to explain how with their skills and enthusiasm the engine was rebuilt to run­ning order, and a stand made to display it.

I first saw Mike’s Ferguson Research engines on one of our regular visits to Coldridge. After a look around the collection, Mike said that he had something to show us. In the back of the workshop there were two prototype engines. At a distance they looked quite complete and I said that “I didn’t think the overhead cam engine would take much to get it going”. How wrong can one be? So, after a little discussion, Mike decided that I would be the one to restore the engine.

Several years passed due to other commitments, but eventually the day came to collect the engine. We had been to the 2018 Dorset Steam Fair and on the way home we arranged to visit Mike and bring the OHC engine to Wilmslow. Rob McCall, a good friend of ours agreed to help me with the restoration of this engine and the whole process has been a joint venture between Rob and myself, with help from Dennis Williamson and lots of helpful advice from Julie.

As soon as we got the engine back to Cheshire, it became apparent that the task was going to be much larger that we first thought. The engine was seized and when the top of the air filter was removed, it was clear that rodents had been using it as a home for quite some time.

Whatever had been living in it, had, in the process, caused considerable damage to the aluminium carburettor bodies.

The first job was to secure the engine before dismantling it. We do have a good engine stand, but as the engine was to be displayed on a stand when completed, the decision was taken to make the frame first. 50mm box section was used for this purpose and Rob welded it all together. The design allowed for the engine to sit on the frame with all the ancillaries to be mounted to the right of the engine. This would allow for an unobstructed view of the engine. The frame also allowed for the sump to sit inside the stand for service and inspection.

Once the engine was safely mounted, the next job was to assess the cause of it being seized. The spark plugs were removed and a borescope was used to check on the state of the bores. The news wasn’t good and the decision was taken to carry out a full strip down.

The engine was completely stripped and it was reasonably easy to free off and remove the sized piston. It was at this point we were able to completely understand and appreciate the design of the engine.

The cylinders are paired front and rear. Both front pistons hit TDC together eliminating a lot of vibration. Throughout the rebuild we have noted several other unusual design features that are not often seen on engines of this era; The pistons themselves are of a complex design, shaped to match the internals of the cylinder head and valve arrangement for efficiency and performance. The rocker shaft mounting posts have one-way valves built in, presumably for maintaining oil pressure within the valve train. Due to the physical construction of a flat 4, the engine is effectively a “dry sump” arrangement relying only on pumped oil for lubrication to the crankshaft, we have no documentation to support whether this was at this stage merely a coincidence of design, or an intentional feature of Ferguson’s to reduce drag on the crankshaft. Perhaps most unusual of all for an engine of this period is the timing being controlled by two independent toothed belts, this at this time was very much in line with the emerging technology of the era and one report actually states that this was a first. The whole engine being a flat four would have had a low centre of gravity and would have suited a sports car/racing car.

The engine block was cleaned up and the cylinders were honed. The pistons were cleaned, but the rings were seized tightly within the grooves and could not be removed intact; so, a new set of piston rings were sourced. They had to be custom made as none of the piston ring manufactures had anything on the shelf that would fit the Ferguson engine, as they were of quite narrow gauge.

Mike had supplied a box of mixed gaskets. It soon became apparent that not all the gaskets were for this engine, but were probably of other variants of similar engines that HFR were working on at the time. Fortunately, we did find a good set of head gaskets that fitted.

The rebuild started and progressed quite well. Timing belts had already been sourced. The correct pitch was not available in the U.K. as it was imperial, but we were able to order a set from the U.S. and when the factory had enough special orders, they batched them.


Looking down on to the restored engine which shows its unique shape.

How to time the engine was still a mystery, due to a lack of technical data. When the flywheel was cleaned up, we discovered two sets of markings. One of these looked to be in the correct place for TDC. Camshaft pulleys had been marked on strip down as their bolt pattern and the lack of a locating dowel allowed the pulleys to be fitted in six different positions. Again, when cleaned up, there were also timing marks on the camshaft pull~ys. When all these marks were aligned, it became apparent that the engine frame had subtle timing marks and everything made sense. Even though everything looked obvious, the engine was rotated slowly by hand many times while observing the actions of the valves until we were completely happy that the engine timing was correct.

The next step was to create starter, fuelling and ignition wiring for the engine. It had come with a distributor, but little else. A control panel was fabricated onto the frame and to this all necessary components and switches to make the engine run. It was at this point a fuel tank and fuel pump were installed.

Due to the previously mentioned damage, a set of carburettors were sourced from a well-known internet auction site. They had to be stripped and checked over. New needles were fitted to the same specification as those in the original carburettors (which took considerable attention to remove). We hope these will give a reasonable performance, but it is my guess that Ferguson had tried many different needle combinations, as there is literature that suggests many different carburettor arrangements were trialled and tested on these engines.

Along came test day and the moment of truth. A battery was connected and a small amount of fuel put in the tank. It took three of four quick attempts and with a small adjustment to the distributor timing, it was running. This test was for about ten seconds as the engine still had no water in it, but it was successful.

An exhaust manifold was made from scratch. No silencer has (at time of writing) been fitted, but the hot gasses are now directed away from the engine. A radiator was fitted to the far right of the frame and hoses routed from the engine to the radiator. This allowed for a much longer test run.

Now knowing that the engine would run and with talk of its first public outing, we turned our attention to safety. A perspex guard was fitted to the front of the engine to protect the timing belts, but still allow full vision. To the rear a mesh guard was made to cover the flywheel.


The restored engine mounted to its new frame with the control panel to the top right.

Just to round off this article, I would like any interested person to feel free to contact me on 07966328600 to make an appointment to view the Coldridge Collection. Likewise Peter Smith and Julie Browning, who have an extensive collection of rare Ferguson tractors and implements, many from the American manufactory, would welcome visitors.

© Mike Thorne and Peter Smith, Ferguson Club Journal Issue 94, Spring 2020