Westbury Whippet Flathead Engine | Enginediy
- The Whippet is an elegant 10cc, single cylinder, side valve, 4-stroke petrol engine. Designed for use in scale model boats, the Whippet was released in 1963 and was one of Edgar Westbury's final IC engine designs.
- Flathead engines, also known as L-head engines or L-block engines, are the most simplistic type of small engine that you’ll find in power equipment. They are often smaller than OHC or OHV engines and less sensitive to low-octane fuel. While they get the job done, they are generally considered to be of a lesser quality than OHC or OHV designs.
What's the OHC or OHV designs?
OHV: Overhead Valve Engines
Overhead valve engines (also called pushrod or I-head engines) are a newer design than the older flathead models, and they’re certainly an improvement. While flathead engines have their valves next to the central cylinder(s), the overhead valve engines put them above the cylinder. This makes them slightly bigger, but they produce more power. Their compression ratios (the higher the compression ratio, the more energy the engine can extract from your fuel) are usually around 8.5:1 as opposed to 7:1 with the flatheads. Bottom line, more power than a flathead, but a little bit bigger.
OHC: Overhead Camshaft Engines
Overhead camshaft engines are generally considered the best of these three engine types. They place the valves as well as the camshaft above the cylinder(s). This means that all OHC engines are technically OHV engines, but not all OHV engines are OHC engines. With fewer moving parts, there are fewer issues that can arise with OHC models. Also, they run cooler and more efficiently than the OHVs. Because they have an even higher compression ratio and are capable of even more RPMs (revolutions per minute), they also produce more power. Of all the types of small engines that you’ll find in power equipment, the OHCs are the highest quality.
History and applications
Flatheads were widely used internationally by automobile manufactures from the late 1890s until the mid-1950s but were replaced by more efficient overhead valve and overhead camshaft engines.
- Flathead cars
Multicylinder flathead engines were used for cars such as the Ford Model T and Ford Model A, the Ford flathead V8 engine and the Ford Sidevalve engine. Cadillac produced V-16 flathead engines for their Series 90 luxury cars from 1938–1940.
After WWII, flathead designs began to be superseded by OHV (overhead valve) designs. Flatheads were no longer common in cars, but they continued in more rudimentary vehicles such as off-road military Jeeps. In US custom car and hot rod circles, restored examples of early Ford flathead V8s are still seen.
- Flathead aero-engines
The simplicity, lightness, compactness and reliability might seem ideal for an aero-engine, but because of their low efficiency, early flathead engines were deemed unsuitable. Two modern flatheads are the Belgian D-Motor flat-fours and flat-sixes.These are extremely oversquare and compact aero-engines with direct drive to a propeller.
- Flathead motorcycles
Flathead designs have been used on a number of early pre-war motorcycles, in particular US V-twins such as Harley-Davidson and Indian, some British singles, BMW flat twins and Russian copies thereof.The Cleveland Motorcycle Manufacturing Company produced a T-head four-cylinder in-line motorcycle engine in the 1920s.
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