Here is a good CFM calculator
http://www.csgnetwork.com/cfmcalc.html

here is a worked example
Now say you get 500CFM...

Next you need to calculate density.
Desnity =

Atmospheric pressure (absolute)/(287 x absolute temperature (in Kelvin))

For regular pressure 99kPa and room temperature your density will be 1.15kg/cubic meter.

500 CFM is 500 cubic feet per minute
1 cubic foot = 0.2832 cubic meters so
500 CFM = 14.15 cubic meters/minute

If you have 14.5 cubic meters of air per minute, and the density is 1.15kg/meter

Then you have 16.3 kg of air per minute

at stoich air fuel mixture thats
1.163 kg of fuel needed per minute

1kg = 2.2046 lbs mass

so 1.163kg/minute would be
2.564 lbs/minute
or
154 lbs/hour

Between 8 injectors you will need
154/8 =
19.23 lbs/hr of fuel flow

A V8 engine like that will need 25lb/hr injectors to be on the safe side.

Did you follow?

at stoich air fuel mixture thats
1.163 kg of fuel needed per minute"

You need about 1kg of fuel for 14kg of air. (the stoichiometric airfuel ratio of 14:1 for gasoline)

so I simply divide 16.3 by 14 to get 1.163kg