What does the 40 / 44 in IDF refer to on the two barrel Webers / Delortas, etc ??Is it CFM , venturi size , just some obscure number that the manufacturer came up with. Also , does any info exist on the airflow ( CFM ) , as in how much ?? I know that ventuiris can be changed , jets and other orifices, can other mods be done to these that would be benificial ?? Is there some other type carb that could be used besides the usual suspects ??
Just wondering what other options besides FI, original or aftermarket.

Jack / Jaxdream

...................36/40/or 44 refers to the butterfly size .(the moveable round things at the bottom of the carburator)..Generally the larger the butterflys the more Airflow will occur..BUT..CFM flow...is dependant on venturi size, and (in the real world) intake port size,shape,finish,heads-ditto-and valve job-and valves....The ideal carburator(s) are dependant on many things and include your engines design non OEM parts-displacement, camshaft,etc..and of course USE....Their are weber IDA,s...46-48-52- and other( larger) Deloroto carburators. But they are generally useful in Racing engines,track cars , drag racing,or autocrossing.

Thanks for the reply , I found a cfm conversion chart on Redlines web site , thier FI setup looks tempting , of course it does require laptop tuning. Thanks again.

Jack / Jaxdream