That's a pretty big motor to run without compensating poles.
Without the field contribution of the inter poles, you may be running in a weakened field condition which will give you over speed and high armature current.
There's an old trick for setting brush positions. I've only used it on exciters, but with an appropriate voltage it will probably work on any size motor. Connect AC to the field. Rotate the brushholders while measuring the voltage at the brushes. Zero volts is the best brush setting that you can determine without running the motor. You can also use the voltmeter leads directly on the commutator.
We had an exciter that failed when it was hot. The internal heating patterns were different depending on whether it was in service or in an oven and it would not fail in the oven in the shop. The shop was reluctant to rewind it when they could not detect a fault. I agreed.
When the exciter was hot I could not find a brush position that would eliminate sparking. I was using the AC test to reset the brushes, and every time the set was stopped, the optimum brush position appeared to have changed.
I then cranked the set with AC on the field and the voltmeter connected.
The voltage at the brushes would fluctuate as the machine rotated.
I relized that I had arranged an "In Place Growler".
Back at the shop, I described the test and the tech ageed that the armature had been proved faulty, and proceeded with the rewind.
It's a quick and easy test of an armature in place.
1> Disconnect the field and the brushes.
2> Connect a voltmeter to the brushes, and an AC voltage to the field.
3> Rotate the machine and watch the voltage. It should be zero. Speed of rotation is unimportant. The test is position dependent and not speed dependent. To check to see if you have enough induced voltage for a reliable test, move the brushes, or test the voltage directly on the commutator between the brush holders.
In your case, I would expect the brushes to be set for full load condition and the no-load brush position will be significantly different.
I would expect the AC field test to show your brushes out of position, but the voltage will be stable as the machine rotates. I don't recommend resetting the brushes until the compensating poles are reinstalled.
Without compensating poles, this test will tell you Two things;
1> Condition of the armature.
(I expect that you will see a small but steady voltage. Steady means good armature, A voltage other than zero indicates that the brushes are off the neutral position.)
2> If the actual brush position is significantly different than the brush position indicated by the test, it is another indication that the motor wants compensating poles. The indicated shift in brush position is an indication of the shift in the uncompensated field flux under load.
yours