Ben and Tom Birchall set a staggering sidecar lap record of 120.357mph as they claimed their 10th TT victory in a row.
In the 100th year of sidecars at the event, the Mansfield brothers second lap of 18 minutes 48.541 seconds lopped nearly 10 seconds off their previous lap record.
This helped the pair's Honda-powered outfit came home 24.066 seconds ahead of closest rivals Peter Founds and Jevan Walmsley who had initially kept the blistering Birchalls honest in the early stages of Saturday teatime's delayed three-lap race.
The Crowe brothers, Ryan and Callum, had looked well-placed for the final podium spot, but they were forced to retire on the second lap allowing John Holden and passenger Maxime Vasseur to claim third, just ahead of Steve and Matthew Ramsden.
Speaking about their historic lap passenger Tom Birchall said: 'Everything just clicked. I knew it was coming.'
Brother Ben had breaking the 120mph lap had been a weight 'on his back for ages.'
Founds was also happy with his fastest ever lap around the Mountain Course. He said: 'We've broken the 119mph barrier now so we'll see what happens in the next race.
He also praised the pair's LCR Honda adding: 'We've thrashed her and she's done us proud.'
Gary Bryan and Philip Hyde were fifth, 2.4 seconds ahead of Daryl Gibson and Tom Christie, the latter making his debut in the driver's seat at the event having competed as a passenger in the past.
Darren Hope and Lenny Bumfrey were 12th, just ahead of fellow Manxies Mike Jackson and Jake Roberts. Craig Melvin and Stuart Christian were 17th, just behind Michael Russell and Vicky Cooke as Russell embarks on another attempt to finish all 10 races at the event.
Dave Molyneux and Dan Sayle were an early retirement, as were Conrad Harrison and Tim Reeves.
Dave Quirk and Karl Schofield were both air-lifted to hospital following a crash at Brandywell on the second lap. Both were reported to be conscious.