It depends on which ones you get and how you adjust them. The ZMax are adjustable, similar to a solid lifter. They must be used with an adjustable valve train, like a solid lifter. If you adjust them normally, there is no noise and they act like a normal lifter. But it's only when you use a feeler gauge and adjust them using the feeler gauge does it put them into their lift reduction mode. Then, they will make noise until about 4000 RPM. But by then, you probably couldn't hear it anyway.
