Ive been wanting to build an rc plane so i ordered all of the parts to do so, the only issue is that my motor/esc dont arrive for another month, hence my curiosity at the possibility of using a brushless car motor
It might work, you would have to make your own firewall to mount your motor. Your motor should also be able to spin a prop fast enough. I don't know much about car motors, but if it has the right rpm's, a 540 size motor should work just fine.
There is no definite answer to your question. Most of the RC car motor are in-runner with relatively long can and running at very high KV. The first challenge is to fine a right gear box, 3:1 or even 5:1, in case your plane is swinging a 9“+ prop. The second challenge is where to place that 7oz, 1300+w, in-runner, with gearbox and 100A Esc into a foamboard plane. So, if you are building a 55” in wing span, over 6lb in AUW, big foam planes, then the answer is “possible”. Otherwise, I would say don’t waste your time.