My wifes 1995 suburban with 70K miles, started making what appears to be a lifter noise at idle and low RPM, once you rev it up the noise goes away. Changed oil and filter but it did not help. added rislone did not help. any ideas how to get rid of the hydraulic lifter noise, how hard is to replace a lifter. I am more adept at working with OH cam engines.

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Thanks, Juan