Aviation Machinist Mate (AD) Week 1 Practice Test

Valve timing in a cam-in-block engine is set by the camshaft and the timing gear, belt, or chain that drives it from the crankshaft. The camshaft has lobes that push on lifters, pushrods, and rocker arms to open and close the intake and exhaust valves. The timing gear/belt/chain keeps the camshaft in the exact phase and speed relative to the crankshaft so each valve opens and closes at the proper crankshaft position for every stroke. Other components like the spark plugs and ignition system, the crankshaft with connecting rods, or the fuel pump do not control when the valves open and close.