747-400:
VMCG
118 - 124 kts
VMCA
112 - 117 kts 1 Engine Out
152 - 160 kts 2 Engines Out
Very simply, VMC calculations generally allow for a slight bank into the live engine. Obviously you cannot bank while still on the ground, you only have rudder, so the VmcG is slightly higher than Vmca1.