| A Studebaker Reference Guide
A short explanation
The modern engine uses a style of valve arrangement called the "I" head. This was referred as the "valve-in-head" engines. There is an elaborate arrangement of valve parts, such as push rods and rocker arms that control the valves. Chevrolet and Buick have had this arrangement since the days of antiques.
Many old cars had a style of valve arrangement called the "L-head" design or more commonly called - "the flathead" This style of engine is easily recognized by the position of the spark plugs set vertically in the heads. A flathead requires only one camshaft, and is the easiest to overhaul because there is no working parts in the head to interfere with head removal. However, the valves in a flathead are harder to service.
The only other kind of spark plug arrangement that has the plugs vertical in the head is the "T" style, but this design has the intake manifold on the opposite side of the exhaust manifold. The "T" head requires two camshafts, one for the valve train in each side of the cylinder.
There are other kinds of valve arrangements that have been tried over the years. There is the "F-head" design that has one valve in the head, and one in the block. There is the rare sleeve valve engine, such as the "Silent Knight". These types of engines are especially difficult to restore because of the great amount of moving sleeve surface that can freeze up.