GM Ignition/Starter quesion
 

First, thanks in advance for checking this out. I have a 1976 Pontiac Formula 400, 4sp, 10k original miles, very clean. I have an issue that I am trying to sort out. When the key is turned to start the car, it will continue to turn over until the car starts, turning the key back does not dis-enage the starter or cease current getting to the starter and taking foot off clutch in gear does not disengage or release the car from trying to start. There are no other issues related to the starter that I have noticed and my thought is a contact in the ignition that may be hanging up, sticking or not returning to position. Pretty comfortable around old cars having had many but have not experienced this prior. I don't want to huck parts at this without asking if anyone is familiar with this. On a side note, the car has been mostly gremlin free which is a fortunate thing.

First: Are you CERTAIN it is still getting current? Is it possible it is just hanging up until it starts?

If you are certain it is still getting juice to the solenoid, then seeing that even engaging the clutch does not stop it, then I believe you have eliminated the ignition switch (assuming the clutch NSS is working. I would check that first. If the NSS is working, then try a remote starter and see if it does the same thing (or if you can get to it with a screwdriver, just do that). If it stays engaged with the ignition switch not even in the start position, then you know it isn't the switch.

Maybe the starter solenoid is sticking.

Is it a GM original ignition switch or a reproduction one? The repros are terrible and the internal "notches" (accessory, start, run) tend to not line up with the position the key is in and it leads to situations just like you described. If it is the original switch then check the column internal linkage rod to make sure the ignition switch box at the base of the column has not moved out of adjustment. This is the plastic and metal contraption with the slider that moves the terminals into contact to activate, start, run, and accessory. The switch box has oval slots for up and down adjustment. They also tend to get filled with dust and crud under the dash and can jam (which may be your issue). I'd remove it and flush it with some brake-clean. Then maybe a light WD40 spray inside to get it to slide smoothly and firmly engage with a "click" in each position. Reinstall, readjust, and see what happens.

When I have a starter issue, I take it to a place that does starters/alternators, last time I took one in it was $10 to fix, the guy also put a new bushing in and some lube.
If in needs to be rebuilt, yiu get your a og back.

It is the original ignition, all other components are believed to be original to the car

I'd still check and see if the locating bolts for that ignition switch box at the base of the column have loosened and let it slip into a different position.

Since pushing the clutch in does NOT stop the starter from turning, I'm with Freddie. Sounds like the solenoid is sticking.

Thank you, makes sense, will update when I sort this out.