If you are building an engine today (~2023), Professionals are not building Hydraulic FLat Tappet camshaft engines? Don't try?

Max1196 said
That is out of a BBC, Gen7 engine, 604 cid. This was in what's called a "gen-set", which is a stationary power plant. That would run day and night for years at near 2000 rpm. It had 1.3 million hours on it, which is about the same as 780000 miles.

SO...it wore out.

It did not have 1.3 million hours on it, that's physically impossible.