Thilthorpe booted three goals in a 20.13 (133) to 5.5 (35) victory - the biggest margin in a Showdown - on a sodden Saturday night at Adelaide Oval.
The Crows will sleep on top of the ladder, though Collingwood will likely retake pole position on Sunday with a win over Richmond.
Adelaide will finish the round no lower than second after logging five consecutive victories for the first time under sixth-year coach Matthew Nicks.
"You dream about performances like that," Nicks said.
The sole blemish on Saturday night was a hamstring injury to Max Michalanney, who was substituted in the third quarter.
The 201cm-tall Thilthorpe defied the heavy rain with his influential 19-disposal display featuring six clearances, and veteran Taylor Walker and Ben Keays booted three goals each.
Adelaide's Jake Soligo (35 disposals) and Sam Berry (20 touches) scored two goals each.
On-baller James Peatling (26, one goal) and captain and 150-gamer Jordan Dawson (21, one goal) were also prominent, while Mark Keane and Josh Worrell ruled in defence.
The Power slumped to an 8-11 win-loss record amid more concerns with Lachie Jones substituted because of a corked thigh and Jack Lukosius suffering a calf injury.
Port vice-captain Zak Butters (34 touches), Ollie Wines (25) and skipper Connor Rozee (22) battled against the tide while Jed McEntee kicked two goals.
"It was definitely a sign of where the two teams are," Power coach Ken Hinkley said.
"Clearly one team is on top of the ladder tonight and the other team is battling to get to the line each week with a few different reasons, whether they be injury or performance."
The match began bizarrely when Port's Miles Bergman roved the first bounce and launched a 50 metre kick - the wrong way.
Adelaide's Darcy Fogarty marked the Bergman blunder and missed the set shot, but the Crows soon created an ominous 3.6 to 0.1 lead.
Port hit back with three consecutive majors of their own - a stunning McEntee shot from a boundary line reduced their deficit to five points at quarter-time.
Adelaide then produced a game-breaking burst, scoring four goals to none in the second stanza as Thilthorpe took control.
The big Crow scored with an audacious 50m left-footer on the run as Adelaide crafted a 29-point half-time advantage, 7.8 to 3.3.
Thilthorpe had 14 disposals, his eye-catching goal and six clearances for the half and extended his influence with the opening goal of the third quarter.
The strike was the first of five goals to Port's two for the term and Adelaide led by 50 points at three quarter-time, 12.11 to 5.3.
And Thilthorpe again took centre stage with the initial goal of a last term when Adelaide piled on eight goals to nil to cruise to victory and a 30-28 overall record against Port.
12°C