Paper 2 · Farm Structures And Machinery
The camshaft of a petrol engine
Acarries the oil from the sump up to the moving parts
Bcarries the current that jumps the gap at the plug points
Copens and closes the inlet and exhaust valves in turn
Dseals the cylinder so that the mixture can be compressed
Explanation: The lobes on the camshaft lift the valves through the push rods and rockers, in step with the crankshaft. That timing is what lets the mixture in and the exhaust gases out at the right moment.
Derived from ZIMSEC Agriculture 5035/2 Paper 2, November 1995, Q19