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It was dropping off at 6200, the customer didn't want to run it higher. It may have been lifter pump up, the preload was about 3/4 turn. I thought about putting heavy duty c-clips in the lifters and running less preload but we didn't have the time.

The drop off might have been the engine going out of tune as far as intake/cam/headers it might have been an RPM they didn't like. I think that is more likely as it sounded good, no misfiring. We have run the stock Magnum lifters at higher RPM on the IMCA V-6.

The dual plane Performer RPM seems to be more prone "going in and out of tune" when compared to a single plane. I had an M-1 ready to test but again didn't have the time.

What has been you experience with an upper RPM limit with the stock hydraulic roller lifters?

Hey jess , sounds like you got to test the heads , We gained about 300 rpm on one of daves hyd rollers by taking almost all the preload out and running just to the clips ,went from 6500 to 6800 ,I think we had 5 degrees more @ .050 also, We were running crane hyd roller lifters with v links / Craig