Only a few minor changes were needed to the bike set-up for the fast five-mile Billown Circuit, in Castletown, as they clocked the fifth fastest lap time in practice of 2min 43.201secs at an average speed of 93.7mph.
They lined up sixth on the grid for race one after a rain-affected qualifying session, but lost a little time at the start after appearing to struggle ti find first gear,
Up to speed on lap two, they got past Blackstock and Rosney into the sharp right-hander of Cross Fourways, and went on a charge to catch the third place pair.
By the end of the third lap they were just two seconds back and caught Harrison and Winkle at Church Bends.
With only three bends remaining, they desperately tried to get past, but on the tight, bumpy course, Harrison used his experience to protect his line and keep Pete and Jev at bay.
They came home fourth, less than a bike’s length back, but a brilliant result in their inaugural Southern 100 Race.
After making a few changes, they lined up in their original grid position of sixth for the eight-lap Sidecar Championship race.
This time they made a better start, passing Harrison and Winkle, and were side-by-side with Pete’s younger brother Alan as they rocketed down the start/finish straight at more than 130mph.
With Blackstock and Rosney holding third, and Harrison and Winkle right behind, they formed a fast quartet on lap one with everyone jostling for position.
Brother Alan made the first move, passing Blackstock and Rosney into Ballabeg to take third position, and Pete and Jev pushed hard and also passed Blackstock and Rosney at Castletown Corner.
A mistake by Alan and Jake on lap three, also at Castletown Corner, saw Pete and Jev up to third, to begin a Battle Royale, as the brothers swapped places several times over the next few laps.
On lap six, second-placed John Holden was forced to stop briefly after an impact, before re-joining the race in sixth.
With new leaders Tim Reeves and Mark Wilkes pulling out a comfortable lead, the brothers continued to pull out the stops and pass each other.
It culminated on the final lap, when side by side at high-speed, Pete and Jev held their nerve, and braked as late as possible into the fast Stadium Bend section, to squeeze ahead into second.
Jev then held a very tight and protective line into the penultimate corner, and as they accelerated towards the chequered flag, Pete and Jev snatched second place by a fraction.
Race organisers and the clerk of the course later unexpectedly declared that Holden/Cain would be credited back their time for stopping to correct their damaged wheel arch, putting them back into second position, and demoting Pete and Jev back to third.
Pete and Jev’s fastest lap time of 2min 33.99secs, at an average speed of 99.36mph, made them the fastest-ever newcomers to lap the Southern 100 circuit.
The pair now turn their attention back to the next round of the British F2 Championship, in Anglesey.