Given certain valve timings, how many degrees will the crankshaft rotate with both the intake and exhaust valves seated?

The correct choice indicates that with both the intake and exhaust valves seated, the crankshaft will rotate 245 degrees. This scenario is important for understanding the operation of an internal combustion engine's four-stroke cycle.

In a four-stroke engine, the cycle consists of four distinct phases: intake, compression, power, and exhaust. Valve timing is crucial because it dictates the opening and closing of the intake and exhaust valves in relation to the position of the crankshaft.

When both valves are seated, it means that neither valve is open, which typically occurs at certain points in the engine's cycle when compression is building or shortly before combustion. The distance the crankshaft rotates during this phase is significant because it helps in analyzing the interplay between the timing of valve events and overall engine performance.

For a certain configuration of valve timing, if it is determined that the crankshaft will rotate 245 degrees while both valves are closed, it emphasizes the relationship between crankshaft position and the phases of the engine cycle.

This degree of rotation has been established through practical engine design and the need for sufficient overlap between valve openings to support efficient engine operation while also ensuring that the valves are sealed during important phases like compression. The selection of 245 degrees reflects an understanding of