The 24-year-old joined the Hammers from Pachuca in July, but is yet to find the back of the net in three appearances.
"He's ready to get the opportunity to go and play," the Daily Star quotes Allardyce as saying. "It will be a great boost for us once he gets out there and produces what he did at the World Cup.
"He scored against Bolivia recently and hopefully he will start scoring for us very shortly. He's one of our major signings and we hope he is going to be very successful."
Valencia scored three times for Ecuador at this summer's World Cup in Brazil.