Seeking knowledge on swaping compressor motors


Been Around the Block
Hey seeking info on swaping air compressor motors. Lets say the current motor is 3hp and we pet a 4.5 or a 5hp motor on it, could just simple do that? Would have to change the pump side as well. Is there anything else I would need to change.

So lets say I change the motor and don't have to change the pump side would there even be an increase in cfm or anything else? Thanx
Its a Puma compressor from NothernTool with 60 gallon tank, 3hp motor, 12.3 cfm(I think), 150psi max.
If you drive the compressor at the same RPM as the old motor, then the compressor performance will be identical. The 5 hp motor will run cooler because it will not be pushing its limit. A 3 hp motor driving a 12.3 cfm compressor is going to overheat if you are actually running near capacity, such as doing media blasting. Is that why you are replacing the motor? I have heard of compressors of this capacity with 3 hp motors going through motors. That kind of capacity should have a 5 hp motor on it.

You might be able to increase your air output a little by using a slightly larger pulley on the motor. I urge caution in that respect, however. Many compressors are designed to run at a specific RPM. If you run them faster, then you might have reliability issues.
There is no descent price compressor to get the job done. Me and my dad have been looking for one with enought cfm,13 or more, and a max psi of 160 You can't get that for a reasonable price.

I hope this compressor turns out to be worth the money...It looks nice Thanx AlphaDogChoppers
I got mine used for $650. It has a 5 hp motor.


we swapped a single stage head with a triple stage head onto a 5hp contractor style compressor. The kind with two tanks. Fills up right quick, runs all of the power tools. Make sure you've got a good pressure release valve on it. We didn't change the pulleyratio so it was running at the same RPM.

We now have a 6.5hp running on it. The only issue if the tank is full, there is too much compression with the head that it's hard to get the motor started. Currently looking for a bigger tank.
jay_kent said:
there is too much compression with the head that it's hard to get the motor started.

I'm not sure you understand your problem.

Compressors have two features to prevent this problem. There is a check valve where the output from the compressor enters the tank, and there is an unloader valve. When the compressor reaches full pressure, the unloader valve allows the pressure on the head of the compressor to bleed off so that when the motor starts, it is not starting against pressure. Different compressors have different ways of dealing with this issue, but they ALL have an unloader to assist motor starting, even cheap portable compressors. If the unloading mechanism is not working, the motor may stall when it tries to start, and that is bad.

When I first got my used compressor, the check valve was stuck. I had to remove it, clean and lubricate it. When the unloader valve would open, it would continuously bleed the tank pressure off. The unloader valve on my compressor is operated centrifugally. On some compressors, it applies pressure to the intake valves to hold them open until the compressor gets up to speed, and it simply bleeds off that valve actuator pressure through an orifice. The motor will run for a couple seconds before the compressor kicks in and starts pumping.
You have multiple problems with your 'pick and mix' approach.
Simplest thing to do is fit an unloader valve in the delivery line to receiver, maybe fit a small tank inline?
Why are you using 160psi?
I don't think I've ever seen any air tool that requires over 90psi, most are lower.
Excessive pressure doesn't get things done faster, just wears stuff out
If your blasting, you should use a larger nozzle, lower pressure and different grades rather than too small a nozzle and higher pressure with a 'fixed' grit size
BTW, tank size is irrelevant to air delivery, I used to work on 80~600 SCFM @100psi tankless compressors (mainly Ingersol Rand)
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