Although L-head inline 4 and 6-cylinder engines were frequently used for automobiles, tractors, etc., the best known L-head automotive engine is the early 20th century Ford V-8, which has both sets of valves (intake and exhaust) located on the inside of the "Vee," and which are all operated by a single camshaft located above the crankshaft. The exhaust follows a lengthy path to leave the engine. This virtually guarantees that the engine will need an unusually large coolant radiator to avoid overheating under sustained heavy use. A flathead design in a V engine, with the air intake/fuel system and all of the exhaust and intake valves inside of the "V" requires that the exhaust gas be passed between the cylinders to outside of the V to the exhaust system. Exhaust heat is thus passed to the coolant (as it exits the engine between the cylinders). In the Ford V-8 flathead design, manufactured from 1932 through 1952, the center exhaust port on the outside of the block exhausts the gasses from two cylinders, exacerbating the high heat problem. This "very hot in the middle" problem makes this particular engine prone to heat-related stress and cracks in the cylinder block. In line engine exhaust gas exits the block more directly and does not cross between the cylinders and is a more temperature-stable design. Whenever exhaust ports and valves are in the cylinder head, exhausting heat has far less time to heat the coolant, and such engines are more durable under high load conditions and a similar sized engine will require less coolant radiator capacity than a flathead V-8.