What is a common characteristic of L-head engines?

L-head engines are specifically designed with the valves located in the engine block, rather than above the piston or in the cylinder head. This configuration, known as the valve-in-block design, is a distinctive feature that characterizes L-head engines. The arrangement typically features a flat combustion chamber, with one or two valves (usually intake and exhaust) positioned side by side in the block itself. This design helps in keeping the engine construction simpler and more compact, which can be advantageous in certain applications, particularly in smaller, less complex engines.

The other characteristics mentioned in the options do not apply to L-head engines. For instance, having valves positioned above the piston is typical of overhead valve (OHV) engines, while a camshaft in the cylinder head is also characteristic of OHV or OHC (overhead cam) engines. Higher power output is generally not a unique characteristic of L-head engines; this trait is variable depending on many factors such as displacement and tuning. Thus, the valve-in-block configuration is indeed the defining and accurate characteristic of L-head engines.