[uiuc240]

I've been looking for a formula to relate CFM to HP, but came up with nothing.  Let's see if we can approximate things based on the amount of air getting in to your motor.  If there is 320 cubic feet of air per minute getting in to your motor, how much fuel will you need?  

Well, first, we know that stoichiometric fuel ratio is 14.7:1...14.7 lbs of air for 1 lb of fuel.  So, how many lbs of air will be entering your motor in one HOUR at 320 cubic feet per minute?

a cubic foot of air weighs 0.07 pounds

so in one minute we have 320*.07 = 22.4 lbs of air entering the motor.  meaning that we need a minimum of (22.4/14.7) = 1.523 lbs of fuel (for all 4 injectors).  
So divide that by 4 = .381 lbs per injector per minute.  
Multiply that by 60 = 22.857 lbs/hr.
Multiply that by 10.5 = 240cc

However, this is for 14.7:1 ratio.  That's not so good.

Let's refigure for 12:1 ratio.

22.4/12 = 1.867
1.867/4 = 0.46667
0.46667*60 = 28 lbs/hr
28*10.5 = 294cc

So, looks to me like you need the 370s.

Oh, and at 294cc (28lbs/hr) you'll be making this much HP:

(28*4)/.5 = 224 hp

How's that?

Eric