A VCT phaser for an internal combustion engine with at least one camshaft comprising
a housing, a rotor, a spool valve and a ring-shaped reservoir. The housing having
at least one chamber and the rotor having at least one vane dividing the chambers
into advance and retard. The spool valve is comprised of a spool mounted within
a bore of the rotor. The reservoir is defined within the bore by an oil dam and
at least one of the spool lands. The spool has a first position in which a chamber
is coupled to the supply and the other chamber is exhausting fluid and a second
position in which a chamber is coupled to the supply and the other chamber is coupled
to the reservoir. When a torque reversal occurs, hydraulic fluid pooled in the
reservoir is drawn into the other chamber when the spool is in the second position.