Hydraulic roller lifters?

[heyoldguy]

I was actually kind of wondering what scenario does need that kind of spring?

I can't say from experience because I've never used spring pressures like that. But I did use 260# IH/760# open on a 280/288 @ .050, .800"/.800" lift camshaft and pull it to 7400 rpm.

It was never intended as a street engine. It was fun however, to drive on the street, set car alarms off and get the thumbs up from those we drove by.