if the valve are adjusted to tight what can happen? how will the motor act?

 

Being too tight means they lift the valve higher, but if not within limits too tight will keep them from seating completely. Back in the solid lifter gas days it meant burned valves. Depending on how much they are out of adjustment they could also cause a very rough running poor performing enjine.

 

It won't lift your valve higher, valve lift is a direct function of the fixed cam lobe. meaning the cam will always lift it exactly the same height every time. But it affects valve timing, IE tight will open the valve sooner lift it the same height and close sooner......effectively advancing your valvetrain timing. {too much may contact the piston too}

if you have no lash and some lift on the base circle of the cam then the valve will never seat, you'll have no compression and no fire in that hole. the valves won't burn because theres no flame. no compression means no fire in a diesel. Dead hole.

 

it could make slightly more lift

 

Not true IMO-

Valve lift is determined by the cam- but the valve lash is the dead way the cam has to lift before the valve opens. So the effective lift of the valve will start later, be lower, and close sooner the bigger the valve lash.

Too little valve lash will keep the valve slightly open, and will reduce compression on this cylinder. But if it ain't really drastic the valve will burn.
The reason is that at the high speed the engine is turning a small opening like a valve just not seated properly will not bleed off compression fast enough to keep the air too cool to ignite the diesel. With the rise of the cylinder pressure due to the diesel injected even the small opening will be sufficient to bleed off a little pressure and the temperature and velocity of the hot gas escaping will damage the valve's seat area and the valve seat.

Just my 2c

AlpineRAM

 

Just think about what you have said. Close clearance will open valve slightly sooner, lift slightly higher, and hold open slightly longer, depending on ramps built onto profile of cam.
To disprove your theory for your satsifaction, miss adjust valve by say .2 inch and see if that valve is opened as much as the next.