Steff, the 1237 PAC looks like what I need. Are you running a Gen 3 hemi? I have not been able to find a solid roller lifter to use. in my 392. I am using the 15820 Comp roller short travel hydraulic,. .060 travel. My first 392 uses the stock lifters and rockers with the Manley Nextek spring. It goes through at 7800 with no problem. I thought that using the Comp lifters with the T&D rockers would add stability to the combination, but something is not right. Like previously stated, the engine went into severe valve float at 7000 and hurt all 16 valves. I am trying to figure what component caused the problem. By the way, the T&D rockers are a piece of art. Thanks for helping. Dyno