Update: I removed the cam, lifters, and pistons from the block. No problems so far. The casting number on the block indicates it is a 1958 235, and the engine has mechanical lifters. Apparently, this means the engine was donated from another truck, because I think I read that all cars had hydraulic lifters by 1958. I've read on this forum that hydraulic lifters are quieter and provide better valve operation at all temperatures. So, my first question is, CAN I replace the mechanical lifters with hydraulic lifters (i.e. are the blocks identical for both types of lifters)? My second question is, SHOULD I replace the mechanical lifters with hydraulic lifters? Is it worth spending a couple hundred bucks on a new cam shaft and lifters? Aside from a little noise, do hydraulic lifters provide more power, durability, or performance?
