[steve25]

Does Butler state this for both street and race?

A hydro lifter ( be it roller or flat tappet) needs a certain above minimum of oil to be able to adjust for any valvetrain clearance that might take place which is why ( if you choose to ) the plunger is adjusted down from its max full travel point that it has.

The roller of any roller type lifter can live with far less oil then a flat tappet type.

It also follows that a full roller rocker can do the same , the caveat is how much oil is needed to keep the valve stems lubed up and to cool the valve springs.

For drag race use the motors are only run for short periods and way up above the rpm of a street motor, so they can get away with less top end oil getting there.

This reduced oil volume needed does wonder for the main a rod bearings in the engine.

Also some solid flat tappet lifters ARE self restricted and there may be some hydro roller lifters that are also, but I am not sure on that .

Here’s what HO racing recommends and with my mostly street motor that had a solid roller cam and full roller rockers I drilled out my lifter restrictors I used in my block to .055”.

Back then the first roller lifters that I used where made by Comp Cams,
and I never had an issue with my 455 that would get rev’ed to 6500 .