General Newb question, lol, but it has been bugging me.

I have always been told put a stick shift in 1st or reverse when you park it on a hill and it wont roll....
It doesn't work. My car rolls backwards slowly in 1st until one of the valves opens, then it rolls. Reverse is better, but still.
Just bugging me. Not sure why this happens.

 

what valve are you referring to? are you also using the parking brake? if you are and it's still moving you need to tighten it.

 

Valves in the engine open on a cylinder because the cars weight slowly moves it. Then it loses compression in the cylinder due to the open valve and it rolls back some until the valve is closed. Then it starts the slowww roll again.
Yes, the parking brake does hold it, but I was always told that I should be able to park it in gear and it wouldn't roll.