I am wondering if this ESC (EZRUN-SC8) can handle a 3500KV motor on 4S... The manual says to use a motor ≤3000KV on 4S. What could happen if Iuse a motor with too high KV???

the higher the KV, the faster the motor spins per volt it is given.

the faster it is spinning, the more amps it draws.

also, most motors have a voltage limit. usually, the higher the KV of the motor the lower the voltage you can put to it(otherwise it just explodes from the centrificual force)

according to the specs, you need a motor with 3000kv or less in order to run a 4s lipo.
"CAN" you run 4s on the 3500kv motor....sure. how long the ESC will last is another question.

also, what motor is it? can IT handle 4s?

most 1/8 scale setups use lower KV motors. then you can get speed by gearing it right. this can provide great low-end punch and still provide insane speeds while pushing all that weight.

Thanks so much for the explanation, it all makes sense now.

its always best to follow the instructions with any ESC or motor. gotta figure that the manufacturer already tested with different motors and found the limits of the ESC.