speedaire compressor cfm unknown

by BJ
(canada)

Is there a way I can roughly calculate the output. It is a reciprocating type V piston arrangement twin cylinder. I can't find the specs for it and am determining whether it is better as a boat anchor or what.
As for repairs, what? I am familiar with motorcycle engines and have pulled the heads on this unit and the flap valves "seem tight" and rust free....no scores in the cylinders and no visible wall wear. Just seems to take a lot longer to fill up the 20g tank(than it use to. Air filter is clean and free flowing and lines are (soap tested) tight and head seal externally is tight (soap tested).