The sidevalve engine was manufactured from the early days of the motor industry right up to the 1960s for cars and is still used in smaller applications.
Many of the early engines were sidevalve as the internal combustion engine evolved from steam through gas to oil burners to petrol. Sidevalve engines are also known as L-Heads or flatheads. This latter name was because the cylinder head is flat – it is a very simple design because it has no valves in it, just a spark plug and fins for cooling purposes.
A sidevalve engine has the valves in the top of the block with each cylinder having a chamber at the top that houses the valves and gives it the name L-Head because the cylinder is shaped like an upside down L. These engines used a simple pushrod system to open the valves from a cam that is mounted near the crankshaft. If you hear the phrase T-Block it will describe a sidevalve engine with the input valve on one side and the exhaust valve on the other making the cylinder look like a T.
The design of the block means that the mixture has a tortuous journey to the cylinder which some say impedes the breathing of the engine and thus reduces power. Some of the engines required a long exhaust as well which meant that the engine got very hot and required a larger radiator to keep it at an optimal temperature.
If you do research on sidevalve engines you will find a lot of descriptions about Ford’s many designs. They built V8s in the US and smaller motors in Europe that were fitted to cars made in the UK and Germany, in fact they went into other cars like Morgans and Simca too.
Harry Ricardo, a British engineer did a lot to improve the life of the sidevalve engine by researching and developing a better air flow in and out of the cylinder. Ricardo’s work ended up in nearly every internal combustion engine because he was the one that worked out the optimal method of delivery of the air/fuel mixture. He also worked out the Octane Rating for petrol. His consultancy firm is still in existence today and owns FF Developments the successor to the Ferguson 4WD system.
With the desire for more power and competitive advantage, engineers were looking at better designs and they found that firstly the overhead valve engine (OHV) produced more power and was cheap to build and then very soon after, the overhead cam engine (OHC) came along.
However, despite having other styles of engines taking large chunks of the market, the sidevalve engine survived a lot longer than expected. Clearly having Ford make them ensured that they would maintain a share of the market, but the flathead was found to be very suitable for smaller capacity engines that again needed to be built cheaply. Chrysler too, used the flathead design until 1951 when it was replaced by the Hemi OHV.
This engine type was used by Harley Davidson quite extensively through the 20s and 30s and they were in production right up to the 70s on some of their bikes and trikes. The engines have been in (and are still used by) Briggs and Stratton powered lawn mowers.