<VV> Re: Jets for power

[Levair at aol.com]

In a message dated 9/21/05 12:06:22 PM Eastern Daylight Time, 
dreamwoodck at yahoo.com writes:

<< The size of the carb is fixed, and as such, hopw much air will flow 
through it is fixed too ( A 390cfm carb flows 390 cubic inches of air per minute) >>

Sorry; not so.
  The cfm rating is by the manufacturer at a certain vacuum drop (which is an 
indication of the flow rate) across the carb(venturi). 
   If you increase the vacuum drop or the flow rate, the carb will flow more 
air and therefore  cause more fuel to mix with the air at a greater rate than 
the flow increase and becomes richer. 
   If this carb is mounted on a 400 cubic in engine at wide open throttle  , 
it will flow more air than mounted on a 200 cid engine and become richer. 
   Supercharging or extensive porting will accomplish the same thing .
   If for instance you have a 600 cfm carb on a 400 cid engine and is 
correctly jetted, it would be too lean on a 200 cid engine and need a larger jet as 
it would not be flowing its rated cfm. 
   
    I have discovered this to be true in practice and not just a theory. 
Warren.