Brian is right on with that kv for hot 4s action ( <-- sounds like LiPo po.rn!). The motor that efflux sells is one option, an ARC 28-47-1 with either a WemoMini or a HET 6904 fan is another, and the Hoffman Storm Hot Wind (HW) is another. Pete (hole digger on RCG) was selling them a few months ago for a discounted price, and the 28-47-1's show up from time to time on here. One thing to note, any ~4200kv motor on 4s is going to draw a TON of amps, usually somewhere around 100-125A. Your batteries will need to be up to snuff.
Best of luck,
EDIT: I see Gary beat me to it!