Australians Rod Pampling and Greg Chalmers sit well in contention midway through the first round of the US PGA Tour event at Torrey Pines.

Pampling compiled a bogey-free eight-under 64 while Chalmers was also mistake free on his way to a seven-under par 65.

The Aussie duo played the easier north course and trail Americans Spencer Levin and Kyle Stanley by two and three shots respectively.

Reigning FedEx Cup champion Bill Haas sits third at nine under.

Pampling, tied for fourth after the morning finishers, flew out of the gates with an opening hole birdie, but his form closing out the front nine was even more impressive.

The 42-year-old punched out four birdies in five holes to go out in 31 shots, enough to hold the solo lead for a brief moment.

He nailed a 25-foot putt on the fifth and hit a beautiful six iron to four feet on the par three sixth to start the run.

A 15-foot birdie rolled into the centre of the cup on the eighth before an easy two-putt birdie on the par five ninth.

The heat cooled for a few holes before the Queenslander dropped in further birdies at the 14th, 16th and 18th holes to beat his previous best mark on the north course by three shots.

Chalmers, tied eighth, raced out of the blocks with three birdies in his opening four holes.

He followed up with further birdies on the 12th and 16th holes before dropping a 50-foot bomb for eagle on the par five 18th.

Gavin Coles was the next best Australian with a four-under 68 (tied 24th) while Nick O’Hern (tied 32nd) posted the best early Australian score on the trickier south course with a three-under par 69.