Hello Ladies and Gents. I'm trying to determine whether or not I have a Lifter bleed down or pump up issue. I believe it's bleed down. Now my engine block is a blueprint 408 short block (Roller block). To get everything up and running with my Lunati 60413 cam, I used stock roller lifters. I have recently swapped to 4.30 gears and found close to 6000+ rpm (at the end of the track) the sucker just kinda levels off and I can feel the odd surge, not quite like valve float. But on the return road back to the pits I can hear the lifters clattering like an old worn out diesel. Wait about 10 minutes fire it back up and everything pumps back up again and sounds normal and runs normal. This leads me to believe that at high rpm the lifters are bleeding down as opposed to pumping up and causing the valves to hang open. Note- I've also noticed the lifters do bleed down pretty quick, I've zero lashed them and set about 1/4 turn for a preload. Just for info, through the traps i'm seeing about 6200-6300rpm. and yes.. I know.. "use a solid cam". I'm looking for some opinions on this. Also if anyone knows of any kinds of lifters that will help alleviate this issue? Thanks!