So by 2002 I was in a position to start making bits. The first items were patterns for cylinder blocks and timing gear case, which I had cast by a local foundry in aluminium.

The timing case included a gear drive for a cooling fan, provision for two further power take-offs (PTOs), and a skew gear 1:1 drive for the distributor and oil pump.

Just when you think the bulk of the project is over, there is the small item of exhaust pipes and carburettors to consider.

The carburettor I've cut from a billet of aluminium, with an integral float chamber of 0.625" dia and choke size of 0.4375" dia. Jet size to be finalised but as a start I've used .020 dia. The design is based on an early 1930 design - very basic.
Constructing a Flat Four Petrol Engine
            -   words by Ron Ebbutt.

For my next project, it was my intention to build an inline four cylinder engine to power an off-highway vehicle. However one club night a colleague offered me a crankshaft, camshaft and something that passed as a crankcase, for a four cylinder engine.

On inspection, the crankcase turned out to be for a flat four engine, but was so poorly made as to be unserviceable. I accepted the parts in exchange for a part finished 'O' gauge steam loco, and commenced a re-design of the 'flat four'.

The cam shaft and crankshaft were very good, so the design was set up around these items.

After several weeks at the drawing board the design ended up as an overhead valve water-cooled engine, with dimensions as shown below.

Dimension Summary

 
  
Cylinders Four
Bore 0.750"
Stroke 0.875"
Capacity 25.34 cc
Compression 8:1
The cylinder heads were cut from solid blocks of spheroidal graphite cast iron, as were the cylinder liners and piston rings. Bronze valve guides carry silver steel valves, while an aluminium cover finishes off and seals in the valve timing gear.

The cooling system is a basic thermo - siphon system with cold water entering the lowest point of the cylinder block and exiting from top of the cylinder head to a radiator. An impellor is to be installed driven directly off the crank-shaft.

The construction of the radiator has taxed my patience, since it consists of 38 tubes and 49 fins, plus top and bottom tanks. This all adds up to something like 1900 soldered joints !

At this point I realised both exhausts and carburettors had to be connected to the engine, and it's surprising how many more components need making to do this.

Oh for the day when it will be fired up !