[PSk]

Originally Posted by AR Larry

Thanks FunkZ. A picture's worth a million.

Along the lines of my origianl post, I actually didn't know the piston could contact the valves. Is this true for most engines?

Yes for most performance orientated ones.

I thought the rev limiter was to protect the crankshaft from unequal forces if the valves couldn't keep their proper timing, but is it's primary function to actually protect the valves?

Rev limiter is there to keep the engine revs under control for all moving components reasons, not just crank and valves. Everything that moves in an engine has a designed optimum speed. Ofcourse the most important thing is the crank, pistons, rods and valves.

Why is it necessary for the piston to travel so far up the cylinder - to increase compression and thus power?

Yes compression ratio ... high compression = more power. The higher the compression the closer the piston must get to the combustion chamber/head and thus valves ...

This is why valve timing is critical .
Pete