you might have to replace the lifters.
Seafoam Motor Treatment.
Sometimes putting a jug of transmission fluid in your oil will clean the junk out of your lifters and stop your noise - if it is an older vehicle with adjustable rockers you can adjust and get rid of the knock.
have your valves adjusted adjust your valves
Hydraulic lifters are nonadjustable. Chances are the noise is coming from play in rocker arm, or ignition out of time. If you are sure it is the lifter, then it must be replaced.
eat something
If they are mechanical lifters, then there is an adjustment under the valve cover. If they are hydraulic then there is no adjustment, and while a different weight motor oil or special additive may help the ticking there is not real way to stop it.
The lifters are in the cylinder heads.The lifters are in the cylinder heads.
1st: STOP the engine!
they have no lifters
the lifters are on the overhead of the engine the lifters are on the overhead of the engine the lifters are on the overhead of the engine
solid lifters at a 012-inch clearance