Argentine veteran Narvaez, 37, had been set to fight Mexican star Daniel Rosas but the youngster withdrew through illness just before the fight.
But some rated fellow Mexican Orucuta as a more likely challenger to catch out the wily Narvaez, who he took all the way in a closely-contested scrap at Luna Park.
The final scorecards – 115-113, 115-113, 110-118 – hinted that it was a difficult one to call, although Narvaez showed the greater discipline against the exciting but at times reckless Orucuta.
Narvaez, who has held the title for 11 years, moves to 39-1-2 (20 k.o.), with his only defeat coming when he tried to step up to bantamweight, losing to Nonito Donaire in 2011.
Orucuta, meanwhile, is 27-2-0 (23 k.o.), suffering his first defeat in two-and-a-half years – the last one having come, ironically, to Rosas.