Porterfield scored the winning goal against Don Revie's powerful and overwhelming favourites Leeds United side in one of the biggest FA Cup final upsets in the history of the competition.
His defining moment came after 30 minutes when he killed a clearance on his left thigh before smashing the ball into the roof of the net with his right foot past Leeds goalkeeper and fellow Scot David Harvey.
It was the only goal of the game and meant Sunderland became the first side from the old Second Division to win the cup for 42 years.
He stayed at Sunderland for another 10 years before moving to Sheffield Wednesday and beginning a long and varied coaching career.
His most recent post was as national coach of Armenia, but he was diagnosed with colon cancer earlier this year.
Porterfield replaced Alex Ferguson as coach of Aberdeen in 1986 and also had spells in club management with Chelsea and Reading before appointments that took him around the world.
He coached Zimbabwe, Zambia, Trinidad & Tobago and Oman, and also worked in South Korean club football.
"His death so young is a tragedy for his family and for football," Manchester United manager Alex Ferguson was quoted as saying on the BBC.
"It isn't long ago when he was coaching in Korea that I spoke with him with the intention of getting a few young players over to United."