Car running rough

[73 ralley]

Looking for some help from you all out there. My BB runns real rough when started so bad you cannot even get the rpms up. I did narrow it down after elimating distributor, coil, unilite ignition. When i unplug either of the field wires off the alternater it runs smooth again even if I unplug both of them it runs smooth, soon as I plug them back in it runs rough. I thought altenator so replaced with new but same thing. I did try an old regulator i had, with no difference. 

Any thoughts?

[Strawdawg]

what is the voltage when the alternator is connected?

[73 ralley]

Voltage with it hooked up is about 12.66 volts. it doesn't change hooked up or not I just can't get any rpm's from it when it is hooked up.

[Chryco Psycho]

I would have the Alt tested , sounds like it is bad , probably shorted & putting load on the alt causing the vibration

[73 ralley]

it is a brand new alt but i guess you get good and bad inn them to. I will take it and get it tested to confirm.
Thanks, i'll keep trying.

[Chryco Psycho]

A friend installed a new Chrome Powermaster alt , it lasted approx 50 miles

[jimynick]

I would have the Alt tested , sounds like it is bad , probably shorted & putting load on the alt causing the vibration
   You should show approx. 13.5-14.2 volts on a healthy alternator, new or not. Check the rotation when you get it off, the bearings may be grabbing, causing enough drag to affect the engine idle. 

[73 ralley]

I dropped the alternator off today, I'll let you know how it turns out.