DerbyDad03 wrote:
My neighbor bought a 2-gallon air compressor at Harbor Fright - the
Central Pneumatic model shown here.

http://www.harborfreight.com/cpi/cta...emnumber=47407

It seems that the input can't keep up with output.

In other words, when he uses the blow gun adaptor, he empties the tank
faster than the compressor can refill it and after a very short period
of time, he has to put the blow gun down and wait until the pressure
builds back up.

Is this to be expected of an inexpensive compressor or is his unit
defective?

Its not a matter of the cost of the compressor but rather one of
capacities. Each compressor will have a CFM rating which is cubic feet
per minute of air at a specific pressure. If the attachment requires
more air then it will drain the reserve and wont operate any more.

For some things like nail guns it will limit the duty cycle, that is ,
you can fire x nails and then have to wait for the compressor to
rebuild the air pressure.