Introducing new chicks!

Help! I have four 10 week olds and three 11 week old chicks. My friend gave me two 10 week olds to introduce. I have the run separated and any chance they get they HATE the Americana. They accepted the olive egger no problem Im assuming because she looks identical to the other two I have but the Americana looks different? How long does integration take? I thought them being youngish still it would be easier than this.