Why do engines with less cylinders rev higher then ones with more cylidners 2 or 4 cylinders opposed to 8?

It's not the amount of cylinders. Formula 1 cars have 8 and they rev to 10,000prms. It's about a shorter stroke and less reciprocating mass. Generally, engines in cars with 4 cylinders have a displacement under 3 liters. This means smaller pistons, rods, crankshaft and/or stroke. Big American muscle has V8's with big displacement, let's say 5 liters or bigger. So they have a longer stroke, bigger pistons, bigger rods and a bigger crank. So that's basically why.