Spencer Leniu has recreated his grand final heroics to inspire Samoa to a comprehensive victory over Papua New Guinea.

Samoa trailed 6-4 at a sold-out Santos National Football Stadium in Port Moresby when Leniu was injected into the contest midway through the first half, with a raucous crowd daring to dream of a Kumuls upset.

The prop, however, had other ideas and produced a match-turning stint reminiscent of his performance for the Roosters in the NRL grand final.

Leniu scored a try, nearly had a second, and ran for 166 metres with 10 tackle breaks in a 38-minute effort. By the time the 26-year-old left the field midway through the second half, Samoa had turned a two-point deficit into a 28-6 lead.

From there, Samoa added seven more tries to close out a 64-6 victory and continue the nation's undefeated start to the IRL Rugby League World Cup.

Ben Gardiner's side has now scored 142 points across the past two weeks and will carry plenty of momentum into next Sunday's showdown with fierce rivals Tonga at a sold-out CommBank Stadium.

Both teams are unbeaten and will be out to secure a semi-final berth.

The Kumuls were outclassed but remain a chance of progressing to the knockout phase with a win over England next week if other results go their way.

It took Samoa just one minute to open the scoring on Saturday after Francis Manuleleua latched on to a short kick-off and raced 40 metres down field. The lock was eventually dragged down before Sua Fa'alogo crossed out wide a couple of plays later.

While Samoa nearly scored a second a couple of minutes later, it was Papua New Guinea who struck next through halfback Bailey Biondi-Odo.

The hosts looked set to extend their lead after a Dudley Dotoi break in the next set but Robert Derby was unable to latch on to a grubber in the in-goal.

The teams traded sets until Samoa coach Ben Gardiner turned to his bench and injected Leniu into the fray.

The prop crashed over for a try in the 30th minute to put his team in front. Leniu nearly had a second soon after but was denied by the Bunker after grounding the ball centimetres short of the line.

Samoa, however, had one last try left in them before the break when Brian To'o soared through the air to tap a cross-field kick back infield to former Penrith teammate Stephen Crichton. The centre juggled the ball but did enough to secure possession to hand his side a 14-6 lead at the break.

Leniu kept the momentum rolling after the break and it didn't take long for Gardiner's side to kick further clear.

Fa'alogo crossed for his second in the 44th minute before Manuleleua crashed over and Hamiso Tabuai-Fidow got in on the action.

By the time Tabuai-Fidow scored his second in the 69th minute, the lead had blown out to 42 points and Samoa showed no signs of slowing down.

Six tries in the final 15 minutes took Gardiner's men past 60 and they will now turn their focus to next week's blockbuster against Tonga.