air compressor rating??

[DanC]

My 60 gallon is a "frankenstein" build from 3-4 different compressors - as such there are no rating stickers or anything of the like on it. Is there anyway to gauge what the cfm of a compressor is?
What is acfm and scfm?
Would there be any benefit to plumbing another tank into the system for more capacity? thanks-

 

[truck]

Anybody have any thoughts on this? As I would like to know as well how to measure cfm.

Truck