Vout can be found by using the formula:
Vout = Vcc * R1 * C1 * Fin
Where Vcc is the supply, Fin is the frequency input.
It is a good idea to make R1 a variable resistor. On making the circuit you may find that the output of the chip isn't quite right, twiddling the value of R1 helps to get the right output.
If you choose values of Vcc=8, R1=40K, C1=47nF and Fin=266 then the output is 4 Volts.
Therefore if the output is linear then we have 1V for every 2000rpm.