what would happen if valve was not adjusted right? and please explain
it could make a hole in your piston
the valves of the cylinder head let fuel in and exhaust gasses out as well as closes off the combustion chamber of the cylinder head allowing the engine to build compression for the firing of the cylinder. improperly adjusted valves can cause a list of problems. one if to tight of clearence is set the valves will not seat all the way and compression will be low as well as to much fuel and so forth. other issue is that it is hard on the camshaft lobes. too loose of a clearence the valve will not open up far enough to allow the appropriate amount of fuel in causing a run issue as well as not enough exhaust gas being pushed out.
The intake valves allow a air/fuel charge to enter the combustion chamber, the exhaust valves allow it to leave. They need to close and seat properly so when the piston comes up on the compression stroke there is plenty of a compressed air/fuel charge for a strong combustion. Without this compressed charge you will have a little fire in the combustion chamber and not an explosion.
Valves let in fuel/air mixture on the intake stroke, hold the combustion chamber under pressure on the compression and power strokes, and let exhaust out in the exhaust stroke of the engine. As you might guess, intake valves control the intake and exhaust valves control the exhaust. If valves are not adjusted right they usually get noisy because the tappets have some distance to move before they press down on the valves. It is much worse if the valves are adjusted too tight - they don't close all the way and hot exhaust gases burn them. It is also possible for the whole valve train to be out of time, which reduces power and fuel economy.
