You've made v = 4.
1/4 *70 = 17.5.
delayMicroseconds(17.5) is nonsense. Delay() should be an int. The processor will ignore the fractional part.
You could adjust the delay to compensate for the slowing effect of Serial.print.
Using the 'blink without delay' principle here might solve it for you, if the lag caused by Serial.print is not greater than your intended 'delay'.