Vilas,
Vmca has absolutely nothing to do with any brand of Vs. Nothing at all. Vmca is about control surface power and thrust lever arms, meaning how much force the deflected controls, mainly rudder, generate and how far from the centre line are the thrust lines of the engines.
All the big Boeings I know about have a Vmca below Vs by a comfortable margin. Perhaps you were thinking of Vlo or even V2.