Why would you remove the powervavles to drag? It seems like all the drag shees that I see spend all of this extra cash to get a T-Rex kit, Cheetah kit, etc. because the power valves provides more power throughout the band. You need to measure the disance from the top of the cylinder down to the port to determine if you can even use a 4mm stroke in it. These monoblocks are stroke specific. As far as removing the powervalves, how long was it ran before you? I've got a set of older powervalved cylinders from an older bike and have been running them hard way past 20 hours with no problem. The CPI in-frames are an excellent choice for this setup.