Brive centre Valbon - who missed the 24-18 Paris loss to Wales with a back strain - takes the place of ankle victim Damien Traille in the French midfield.
Laporte's second enforced change sees Heymans - fit again following thigh trouble - returning for bustling winger Aurelien Rougerie, who damaged his collarbone against the Welsh.
Toulouse giant Fabien Pelous will lead France in Dublin, on the occasion of his 100th cap - as the 31-year-old joins a select band of the international game's centurions.
Speaking today, coach Laporte admitted he has no fears over his untried midfield tandem of Valbon and Heymans - who boast just 12 Test caps between them.
"Valbon is a very talented player," insisted Laporte.
"I'm sure he will be eager to prove his worth and to face O'Driscoll and D'Arcy, who are one of the best centre partnerships in the world.
"The Irish don't know him yet, but they are going to discover him.
"Heymans was an obvious candidate. He has won 10 caps, he was with us last November and he is back to his best after being sidelined by an injury."
Pelous will skipper France for a 32nd time.
In the replacements, uncapped Toulouse back Benoit Baby, lock Pascal Pape - who has recovered from an ankle injury - and prop Pieter De Villiers return.
SIX NATIONS: Saturday, March 12Ireland v France, Lansdowne Road, 1.30pm
(15) Julien Laharrague (Brive)(14) Cedric Heymans (Toulouse)(13) Yannick Jauzion (Toulouse)(12) Ludovic Valbon (Brive)(11) Christophe Dominici (Stade Francais)(10) Yann Delaigue (Castres)
(16) William Servat (Toulouse)(17) Pieter De Villiers (Stade Francais)(18) Pascal Pape (Bourgoin)(19) Gregory Lamboley (Toulouse)(20) Pierre Mignoni (Clermont)(21) Fridiric Michalak (Toulouse)(22) Benoit Baby (Toulouse)
Referee: Tony Spreadbury (England)Touch judges: Paul Honiss (New Zealand), Nigel Whitehouse (Wales)