Newer vs Older

RustyRatRod said
I have read the hydraulic lifter slants did not run as well and were problematic........no direct experience, so that may certainly not be the case.

@slantsixdan would be your best bet to answer this. Maybe he will chime in.

That would be due to the Lean Burn system that was ran on the hydraulic lifter slants but the actual engine itself was fine. Remove it for a conventional setup and there's nothing wrong with the engine at all.