The four race favourites - Porte, Alberto Contador (Tinkoff-Saxo), Fabio Aru (Astana) and Rigoberto Uran (Etixx-Quick-Step) - finished together on the Campitello Matese at the conclusion of the 186km stage.
Race leader Contador managed to snatch a two second time bonus during a sprint earlier in the stage to double his lead to four seconds on Fabio Aru (Astana) and 22 seconds on Porte.
While Contador was left without team-mates, Porte was well supported in the mountains and was able to respond to Aru's attack.
“I’m so happy how it went," Porte told reporters after the stage. "(Sebastian) Henao was fantastic, Mikel Nieve and (Leopold) König put up that big effort. It was great. I’m feeling good too.”
In the past it has been a familiar sight to see Team Sky driving the front of the peloton, but with Porte third, the team is content to leave the grunt work up to Tinkoff-Saxo and Astana at this stage in the race.
“We’ve been good with how we’ve used our team,” said Porte. “Some people perceived it as weakness, but I think it’s more strategic, we don’t need to ride if Astana and Saxo want to take the race on.
“I think the second and obviously the third week is where we are going to need fresh team-mates.”
The peloton faces it second day in the medium mountains on Stage 9 with 215km from Benevento to San Giorgio del Sannio.