Hmmmm guess over the last 20 years of building engines I've been doing it wrong every day. I'll call my friend (the head engineer at comp) and tell him that we've been wrong all these years

Here is from engine builder mag. Given to them by erson cams http://www.enginebuildermag.com/2012...ing-pressures/

I'd love to see if my hyd rollers would rev cleanly to 6500rpm like they did with 130/300 psi springs lol

Anyhow, in my Mercury racing manual, spring specs for the HP500 engine, are

150 lbs closed at 1.900
420 lbs open at 1.300

They will and free up extra hp.

Good way to make friends here. Stick around though, you might learn something. There's quite a few here running 1200hp hydraulic roller engines, that might know a thing or two. Hint, they aren't doing it with 300lbs over the nose

There's always exceptions lol if you want higher spring pressures on hydraulic roller cams use short travel lifters that's the reason they make them.

Looks like crane's recommendation is a little different than Erson's. Crane might know a thing or two, considering they have been supplying mercury racing's camshafts and valvetrain specs since the 80's.

http://www.cranecams.com/bulletins_listview.php?s_id=16

130 to 160 not that diffrent I'm doing a 598 for a jet boat right now that's going to the dyno I'll video the spring pressures and a dyno sheet if you want or I have a pair of 525's for a fountain. But that said if your forced induction you will need more spring pressure due to boost negating spring pressure.

But always go with the cam manufacturer recommendations. The numbers I gave are a general rule and will work.

You said 150 will start collapsing the lifter. Its not the seat pressure that collapses a lifter, it would be the nose pressure. A stock HP500 crane lifter, will work fine with the 420lbs over the nose, as it has been proven in the Hp500 engines. A morel lifter, or Johnson, can take a heck of alot more open psi than that, and still handle it. Heck, the 5045 morels, recommend 550-575lbs open.