The Matt Stone Racing driver, on a high after a second career win in Darwin last time out, gapped the field by two-tenths in the second and final practice session in Townsville.
His 1m13.432s came as part of a qualifying sim right at the flag and left him a healthy two-tenths clear of the chasing field.
The session-topping effort followed a subdued practice 1 where Le Brocq was just 18th fastest.
"[It was] just tyres; we didn't use any [greens] in the first session so what we started with wasn't the best," explained Le Brocq.
"It's good. We had a few changes we wanted to get through, we had a bit of a swing at it from practice 1 to practice 2.
"I had no time on my dash, so I had not idea what time I had done. It's awesome, but it's early days. We'll see if we can back it up tomorrow."
Until Le Brocq's late heroics the benchmark was Bryce Fullwood, the Brad Jones Racing driver setting a 1m13.679s inside the first 10 minutes.
That time was still good enough for second as the likes of Cam Waters and Shane van Gisbergen fell short at the flag.
Waters ended up third and best of the drivers in the revised Ford Mustang. There were still only three Fords in the top 10, though, with Matt Payne in eighth and James Courtney in 10th.
NASCAR sensation van Gisbergen was fourth ahead of fellow Kiwi Andre Heimgartner and title contender Will Brown.
Scott Pye was seventh while Broc Feeney slotted in between Payne and Courtney in ninth.
Points leader Brodie Kostecki had another quiet session, the Erebus driver just 14th fastest.
He had been on for a big improvement at the flag, going purple in sector 1, only to end up down an escape road in the middle sector.
The next time Supercars hits the track will be for qualifying at 10:15am local time on Saturday.
Townsville 500 Practice 2 results
| Cla | # | Driver | Car | Time | Gap |
|---|---|---|---|---|---|
| 1 | 34 |  Jack Le Brocq |
Chevrolet | 1'13.4320 | |
| 2 | 14 | Bryce Fullwood |
Chevrolet | 1'13.6790 | 0.2470 |
| 3 | 6 | Cameron Waters |
Ford Mustang GT | 1'13.7641 | 0.3321 |
| 4 | 97 |  Shane van Gisbergen |
Chevrolet | 1'13.7642 | 0.3322 |
| 5 | 8 | Andre Heimgartner |
Chevrolet | 1'13.7691 | 0.3371 |
| 6 | 9 | Will Brown |
Chevrolet | 1'13.7950 | 0.3630 |
| 7 | 20 | Scott Pye |
Chevrolet | 1'13.8127 | 0.3807 |
| 8 | 19 | Matthew Payne | Ford Mustang GT | 1'13.8143 | 0.3823 |
| 9 | 88 | Broc Feeney | Chevrolet | 1'13.8452 | 0.4132 |
| 10 | 5 | James Courtney |
Ford Mustang GT | 1'13.9008 | 0.4688 |
| 11 | 26 | David Reynolds |
Ford Mustang GT | 1'13.9320 | 0.5000 |
| 12 | 55 | Thomas Randle |
Ford Mustang GT | 1'13.9483 | 0.5163 |
| 13 | 17 | Will Davison |
Ford Mustang GT | 1'13.9669 | 0.5349 |
| 14 | 99 | Brodie Kostecki | Chevrolet | 1'14.0258 | 0.5938 |
| 15 | 25 | Chaz Mostert |
Ford Mustang GT | 1'14.0657 | 0.6337 |
| 16 | 23 | Tim Slade |
Chevrolet | 1'14.0969 | 0.6649 |
| 17 | 35 | Cameron Hill | Chevrolet | 1'14.1179 | 0.6859 |
| 18 | 18 | Mark Winterbottom |
Chevrolet | 1'14.1531 | 0.7211 |
| 19 | 2 | Nick Percat |
Ford Mustang GT | 1'14.1767 | 0.7447 |
| 20 | 3 | Todd Hazelwood |
Ford Mustang GT | 1'14.2110 | 0.7790 |
| 21 | 31 | James Golding |
Chevrolet | 1'14.2524 | 0.8204 |
| 22 | 11 | Anton De Pasquale |
Ford Mustang GT | 1'14.2581 | 0.8261 |
| 23 | 4 | Jack Smith |
Chevrolet | 1'14.3201 | 0.8881 |
| 24 | 777 | Declan Fraser | Ford Mustang GT | 1'14.4466 | 1.0146 |
| 25 | 96 | Macauley Jones |
Chevrolet | 1'14.7520 | 1.3200 |
| View full results | |||||
