1999 jimmy rear engine knocking

My 99 jimmy with 230 klms/170 mi. started knocking and it sounds like it’s coming from the top rear engine area, had it to several mechanics that say its a ristpin, or collasped lifter. I have the lifters out now and they all look good , should I just replace them or can I test them some way to see if that was the problem. I’m stuck not knowing my next step.