Stewart Cink has capped off a dominant, record-breaking week by winning the PGA Tour's Heritage title for a third time.

The 47-year-old Cink carded a steady, stress-free 70 on Sunday to finish at 19-under 265 at Harbour Town to seal a four-shot victory.

Argentine Emiliano Grillo (68) and Harold Varner III (66) were tied for second.

Australian Cameron Smith, who led the tournament after his career-low 62 in the opening round, fired a bogey-free 66 to claim a share of ninth at 11 under.

Smith's hopes of a third PGA Tour win faded on Friday with a 71 while Saturday's 74 ended them.

Cink hugged his son and caddie, Reagan, after his closing par on the 18th green.

The duo were then joined by Cink's wife Lisa and their other son Connor to celebrate.

"I don't even know if I have the words," Cink said.

He won for the second time this season - only he and Bryson DeChambeau have done that - and continued his resurgence on the PGA Tour at a time when many professionals his age are looking ahead to the PGA Tour Champions.

Not Cink, who broke a 12-year winless streak last in September and added five more top-20 finishes, including a tie for 12th last week at the Masters.

He won $1.278 million ($A1.7), almost as much as the $1.404m ($A1.8) for his two previous victories at Harbour Town - in 2000 and 2004 - combined.

Cink is also just the fourth player to win twice in the same PGA Tour season after turning 47.

Sam Snead, Julius Boros and Kenny Perry, who accomplished it twice, are the others.

Cink put on show for the ages - shattering the lowest 36-hole score and 54-hole scoring mark at Harbour Town.

Cink carried a five-shot lead into the final round and dared all chasers to come get him.

Nobody made a run at Cink, who led by at least three shots throughout.

PGA Championship winner Collin Morikawa, paired with Cink in the final round, had a 72 to srop back to tied-seventh.

Top-ranked Dustin Johnson closed with his best round of the tournament at 66 to finish tied for 13th at 10 under.

Smith's fellow Australian Cameron Davis jumped up 11 spots to a share of 25th after a closing 68 in another solid week.