You don't ever want to uncover the lifter oil galley. Even a minor amount of valve float can create a gross internal oil leak.
High RPM + Loss of Oil pressure= Bad Things happening
I'd be uncomfortable running the converted hydraulic lifters. I would be afraid of failing the roller axles and needles. I think the tie bar issue could happen on that style lifter as a mechanical or hydraulic lifter.
As a hydraulic lifter, the roller, axles and needles have a hydraulic cushion to soften the blow of the eccentric rapidly pushing on the roller. Plus hydraulic cams have a gentle take-up ramp that also tend to cushion the action of the eccentric.
Mechanical grinds don't have the take-up in the lobes and the lash will impart a small shock to rollers and axles that were never intended to see that shock load.
I know that roller axles and needle bearing are prone to failure on mechanical roller lifters. That's why I like the Isky's. Isky will rebuild their lifters for 11 bucks a piece.
BTW, I was facing the same problem with one of my S1 blocks. I solved the problem by selling the block and buying a S2 block.
Dave
