Originally Posted by retroshark
just a quick question, why is it bad to rev your car in neutral/out of gear? im not gonna lie, ive done it a handful of times, but its not like ill always throow it into neutral and rev at people. i did it i think once when i put my intake on, once to rev the engine for a friend and maybe another once or twice. what exactly does it do? im guessing its a long the lines of just stressing the engine?
I did too when I didn't know anything about cars.
It puts extreme forces on just about everything in the engine, especially the crankshaft and connecting rods, because there's no force that's holding the engine back from revving freely. Out of gear there is no resistance and the engine will spin very quickly and freely, but if you rev too high or a lot you're risking everything - piston rings, head gasket, etc. That's what I've read and heard. In gear it's totally different because you have the resistance that the transmission is providing.