knocking.... at random times

well figure this one out guys---- i put in a new set of lifters then i ran the engine again yesterday and it did the same thing... i did a compression check

1= 150psi
2= 150psi
3= 145psi
4= 150psi
5= 150psi
6= 145psi
7= 150psi
8= 0psi

dead cylinder - we turned the motor over and we heard the knock and then hole#8 had 150psi.... we started the engine and it ran great then after about 45 seconds it knocked and then started to sputter and die... it seems to be while running, it is dropping the #8 hole.... it seems to be a valve is sticking and knocking the piston top... thus also making no compression and killing the motor.