I got an instruction from Alretta Truck Parts together with my remanufactured hydrovac.
.
It says 30cc or one oz for a singel piston 5 1/4".
Same for a 6 3/4" piston.
For a singel piston 9 1/2" it shall have 60cc or 2 oz.
Same volume for a tandem piston.

He added USE HYDRAULIC JACK OIL with a ink pen.

So I followed that advice.

My Chevy Viking 1959

Ulf Hedlund. Eskilstuna. Sweden
[email protected]
Also:
Ford Galaxie 4 dr 1959
Ford Custom 4 dr 1964
Ford Mustang GT 2005