Anyone know about rebuilding old air compressors??

[HardcoreZ28]

Someone gave me an old (1960's-70's) Kellog American air compressor last year for my shop. I pulled it all apart at the time and finally got back to finishing it this past week. The thing is HUGE. It's probably an 80 gallon tank and a dual piston setup with a 3.5hp motor turning it.

The rebuild kit I got had new rings, bearings, gaskets, piston pins, and valves for the head. With the exception of a loose counterweight on the crank all of the parts seemed to be in pretty good shape. Myself and a few professional welders couldn't find an easy solution to tightening up the counterweight because of the difference in materials used for the weights vs. the crank so I just reassembled it. Had very little play in it but enough that I would have fixed it if I could.

Well after remounting the compressor and motor on the tank and rewiring it last night I fired it up for the first time. Motor runs fine and it does put out air, however I feel like the volume is very, very low. It took a good 20 minutes to get the tank pressure up to about 120psi and wouldn't really go above that....and it didn't activate the switch to kick off the electric motor. The only two possibilities I can think of are the pistons aren't sealing and I'm getting tons of blow by......or maybe I did something wrong rebuilding the head. The valves basically were a keeper that screws in that holds down an octagonal washer and a spring. The only difference between the high and low pressure valves was the order of the spring and valve (washer) and I'm almost certain I got them right as I did one at a time. Only other possibility I can think of is that one of the intercooler hoses out of the head is plugged badly.

Any of you guys know about these old beasts? Any insight?

[LTb1ow]

Got any numbers stamped on the compressor?

[WildBillyT]

How old is the motor?

[HardcoreZ28]

I'd have to pull the numbers when I get home....it has an ID tag on it. I believe it's something like a 331.

Unsure on the age of the motor but it seems to be turning fine and at a decent speed.

[sweetbmxrider]

just a tidbit, mine is set to kick on around 120 psi and shuts off around 150-160. the initial fill would take a little i would imagine but seems like theres an issue/issues if it stops at 120ish.