It refers to an engine where the area occupied by the valves when they are open is occupied by the piston when the valves are closed. If the timing belt lets go while the engine is running the piston will smash the open valves doing loads of damage.
The valves in a car engine are opened and closed by a cam shaft driven by the engine crankshaft. they allow the flow of gases and fuel into the engine and the burnt gases out of the engine into the exhaust system.
If the timing belt broke on an interference engine, the open valves and pistons would collide and wreck the engine.
The blood rushing through the valves as the open and close - thump-thump-thump. . .
a cam in engine is to operate the lifters which in turn open and close the inlet and exhaust valves
overlap
Its purpose is to open the right valves at the right times.
Semilunar valves are open when the blood is being pumped. The AV valves are closed when the semilunar valves are open.
The way you explain it it sounds like your engine has hydrolic lifters. With these I have always tightened the rockers until the pushrod gets hard to spin and wont move up or down and then ONE HALF TURN not a full turn. The valves might open but within a minute or so should close. This is cause by the lifter bleeding off leftover oil in it. Hope this helps.
Unfortunately yes. The Saturn motor is considered an Interference motor. When the chain breaks the neutral landing position of the camshafts will allow valves to be open, as the engine slows down from its rotating mass it will bend these open valves.
Worn valves will not seal completely, will not open completely, or open as far as they should. This will cause incomplete combustion, backfire of exhaust gasses, release of compression, and escape of oil into the combustion chamber. Engine will lack power and smoke.
Referring to the Auto Education and Gates (commercial) websites (refer to the links, below), the 2003 Kia Rio is referred to as an "interference engine", which means that, as with many other motor vehicles, "(i)f your timing belt breaks, the engine will continue to turn, but the camshaft stops. If any of the valves are open, and your engine is an interference engine, the piston will slam into the open valve and cause some real expensive damage", including, potentially, needing to replace the entire engine. This does not cause the valves to "bend". the valves bend, I'll ship you the bad valves.