A contact insertion machine includes a contact feeder having a feed finger configured to feed contacts of a power connector assembly in a feed direction along a feed track during a contact loading process. The contact insertion machine includes a power connector assembly holder holding a housing of the power connector assembly and movable relative to the feed track to position the housing to receive the contacts in a contact stack. The contact insertion machine includes a contact retention plate located upstream of the power connector assembly holder having a contact insertion port therethrough. The contact insertion port is aligned with the feed track downstream of the feed track. The power connector assembly holder is movable relative to the contact retention plate to position the housing to receive the contacts through the contact insertion port.