Holden's stranglehold on the V8 Supercar Championship has showed no sign of easing as Mark Skaife topped the practice charts at Darwin's Hidden Valley Raceway.

But it was Ford pair James Courtney and Craig Lowndes who stole the spotlight with a fine display of sportsmanship.

Courtney slammed into a tyre wall, rolled his Falcon BF onto its roof and Lowndes stopped and helped free his rival from the wreckage.

Courtney walked away unharmed and the car suffered no serious damage, meaning both man and machine will be fine for Saturday's qualifying session.

"It's good to know that even your fiercest competitors care about your welfare," said Courtney, who was involved in a frightening 300km/h accident during Formula One testing at Monza in 2002.

"These cars are actually quite difficult things to get out of, especially when they're upside down, so Craig's help was very much needed and appreciated."

Skaife, who surpassed the late Peter Brock's record of 37 round wins at Eastern Creek two weekends ago, went around the 2.9km circuit in 1min:09.2616secs, a quarter of a second quicker than series leader Rick Kelly (1:09.5227) with Ford's Mark Winterbottom (1:09.5983) third quickest.

The inaugural Darwin champion, Ford's Russell Ingall, was next best in 1:09.6126 and Todd Kelly (1:09.8049) rounded out the top five.

Courtney was sixth with a 1:10.4165 before the midway point of the 50-lap session when the incident occurred, and in the end his time was only good enough for 21st.

"It was a pretty pathetic effort as far as roll-overs go, there was no real speed," added Courtney, more embarrassed than shaken.

"I'm fine, I'm just annoyed I couldn't get out there for the rest of the practice session because the car was going good up until then.

"It wasn't a big impact. It was quite a long spin, it happened quite early on the corner and I'd wiped most of the speed off before I actually got onto the dirt.

"There's no run-off there so I just hit the tyres and went over.

"I would have driven back if I'd landed on the wheels but it's a bit hard when it's on the roof - no traction," he joked.

"It looked worse than it actually was."

Saturday's qualifying will be followed by the first 42-lap race in the afternoon.

Two more 42-lap races close out the round on Sunday.

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