Weird starter issue

[WS6]

I have never seen this happen before but it happened today on a 66 427 vette. This car is nearly a 100 point NCRS car. When you tried to start the car the starter would continue to turn even after turning the key off and removing it from the ignition. We were not trying to start the car so it never fired off. It would just turn over and over until the battery was disconnected. Thank goodness for a quick disconnect. Anyway, we tested the switch, the wires, and eventually decided to replace the silenoid after testing it and thinking it was the culprit. It wasn't the problem. Luckily I had a 71 454 vette that I could pull the starter off of. I did so and the 66 started fine and acted correctly with that starter. Oh and once it would do it's run on thing, I could disconnect the battery and then reconnect it shortly there after(within a minute) and have the engine start turning over on its on even with the ignition switch laying on the floorboard of the car.

Has anyone ever had this happen to them? Any idea on what it could be? If you had walked up to me and asked me if the starter motor itself could cause this I would have said no way. This was completely weird to me. The owner will send his factory correct one out to be rebuilt and hopefully they can tell us what happened when they pull it apart for restoring. Thanks

[LowBuckX]

Never heard of GM starters doing this but I have replaced many ford starters that did it. I have no answer why but like said I have seen it in Ford starters with the divorced solenoid, Replaceing the solinoid didnt fix it either it was internal in the main body. Sorry no help but your not alone.

[Turbo Hen]

Its happened to me before on a SBC in a full size van....the starter is sticking & you'll need to replace it. Im pretty sure it wont go away with changing the solenoid spring either, it may be the brushes sticking ON inside the starter.

-Carm

[MonzaRacer]

You will find that either it has a worn pulling yoke or the piston inside the soleniod is deformed or damaged.
Its not uncommon.
Another thing is that the s terminal wire was wrapped around the battery cable and was gettingunduced current but I would figure its in the pullin yoke being worn/damaged. when tearing starters down to swap noses or replace brushes in pinch you see the yoke worn and it causeing lots of problems or on a new starter the rebuilder just migs up the wear and sprays it with water for a super hard repair.
Lee Abel
PS oh yeah most people think the starter starts turning when the solenoid gets power but it wont start turning till that little piston pushes the button way back in the back of the solenoid. figured this out at a young age as I found out you need to know the length of the old solenoid cause if you have a short solenoid piston and a deep solenoid it will click and not start, then had to figure out how to get the other piston/yoke out and into my starter then it started(parts tarter was junk but solenoid was new)