Reply to "Theoretical question. Hydralic roller vs solid roller"

Theoretically you loose zero.

The problem with hydraulics is that you never get 100% of the lift because it is the oil pressure that provides the resistance to the lifter.
The more pressure you have the more efficient the lifter is. It is never 100%.

Solid lifters in a Boss head aren't hard to maintaine at all. It is the Chevy solid lifters that have given solids a bad name.

Roller lifters theoretically give you more area under the curve because the lobe can be cut closer to the optimum ramp angle for faster valve opening.

That inturn maximizes the port velocity and effects mostly more torque, but a couple of hp too.

Roller lifters are in current production engines for fuel efficentcy and emmissions (remember the zinc you need for lifters that the cats don't like).

There is no performance reason to add roller lifters to an engine that will only see 6000rpms on an non-emmsissions engine. It's a waiste of money.

The answer to the question is how efficient your hydraulic lifters are. Are they 98% efficieint? What's 98% of 600hp? 588hp.

You lost 12hp because of hydraulics.

Keep in mind that the roller lifter assembly is heavier then a normal lifter. To compensate for that you need to add spring pressure.

The spring pressure pushes back on the hydraulic lifter and you get less lift then normal. How much? Who cares?