the air compressor is on a 1941 aec matador for the air breaks after having problems with our air compressor (because the screw in the valve had worked lose and shattered the top of the piston to bits) we replaced it with a second hand one that we was lucky to find it seams to be working ok but the air pressure will not go up any more than 40 psi/lbs, the gauge pressure should rise until the governor "cuts out" at 90 lb. per sq. in. does anyone please have any knowledge about this kind of stuff? if so we would be very grateful thanks
would it be possible to make 1 good compresser out of the 2 ? and do you think this could help?

I am looking at buying a air compressor and harbor freight is the cheapest and the best it seams they sale this brand called central pneumatic. The air compressor is 21 gallons and is a 3hp motor. It also has a 7 scfm @ 40 and a 4.9 @ 90 and a 4.3 @ 115 is this a good air compressor from harbor freight. Or should i stay away from the brand.