Guys, thanks for the info.

Quote: Speed Pro on SPHT969R
"Speed Pro Hi-Rev (commonly called anti-pump up) hydraulic lifters feature a special high strength steel retainer used in place of the normal spring clip to precisely limit the travel of the plunger during operation. With plunger travel limited, adjustable rocker arms must be used to effect a lash adjustment of .000/.002''. This then allows the valve train to perform more like a mechanical system. Hi-Rev hydraulic lifters can be identified by the prefix "SPHT" and the suffix "R".

That is the worst written piece of...
Basically, by replacing a cheap spring clip with a circlip, only now will you limit the plungers travel.
And what does that have to do with adjustable rockers or needing zero lash (or preload).

Anyway the manifold is back off and the lifters are out.
Lifter 2 small.jpg
Race on the left, holden stock on the right.

Chrisp