So i just tore into my engine, removed the heads thinking the reason for my running problems were a cracked head or bad valves. Looking like they are not the issue but instead maybe piston rings are bad. What i am wondering since i have this torn apart and will be pulling the block out of the rig here soon is has anyone ever bored out a 4.0 OHV engine before and had noticeable gains? Is the money worth it in other words. Thanks for the feedback!