Factory original new "milk can" solid lifters do not have a crown- - - -they're totally flat across the bottom. We spent a lot of time checking that with a precision machinist's square on the lifters we installed while building John's 261 about a year ago. The lifter bores on a stovebolt six are slightly off center on the cam lobes, which promote the lifters rotating as the cam lobe contacts the lifter. Hydraulic cams have a very short acceleration ramp, usually less than .005", compared to the ones on a solid cam that takes up the adjustment gap before starting the rapid lift of the valve off its seat. There's no way to swap hydraulic lifters to solids or vice versa because of a completely different cam lobe profile.
If a rod bearing failed during a properly done solvent flush, the problem was there to begin with. I've done the Diesel flush at least 50 times with no failures so far.
Jerry
