Friend of mine has an LT1 and when he takes the key to OFF the car doesn't stop anymore. I asked him if he did any wiring....any minor insignificant wiring at all? He said no, so I'm wondering what might a cause? any pointers?

 

Faulty ignigtion switch?

 

I checked that. The "run/after start" position stay energized when going to "OFF" (with the lead attached). If I take readings with the lead removed, then the "run/after start" terminal actually goes dead.
He has this LT1 in an old car, and I read somewhere that there might be some feedback and I might be able to install a diode, in a lead somewhere, to prevent this feedback. Any ideas?

 

Well I had this same issue on my LS1 transplant and if I remember correctly the wire going to my thirdgen fuse block was not an igintion hot wire it was hot 24/7. After fixing that the car turned off.