Starter won't disengage...Please Help!

I am building a 1972 monte carlo and I am having a problem with the starter not disengaging when we try to start it. When we turn the key the engine will turn over and fire but we have to disconnect the battery cable to get the starter to disengage. And then by just touching the battery cable to the battery terminal, the starter will engage itself again.  We are working with a new crate motor so chances seem slim that there are any problems with the starter itself, and it did the same thing with the old motor anyways. I have done a lot of research on the wiring of the starter and although I do believe we have it wired correctly, feel free to give advice that might prove otherwise. I have read a little about the starter bendix, and I am not completely familiar with this part, however I heard it mentioned quite a few times when searching for solutions to this problem. It is a 350 engine and I am running an HEI distributor. Thanks for any help.  

Sounds like the starter solenoid is sticking.  
Professional hi-performance engine builder

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Yea but it was doing the same thing on the previous motor, with a different starter....I guess its still possible, just seemed unlikely that both starters had a bad solenoid. But we'll check into it. Any other input is welcomed.  

there are 3 terminals on the starter... the top post is for the battery cables and the fuseable links that power the truck...  and the alternator..

the "S" terminal ... right side of the solenoid hooks to the what used to be purple wire... that only gets power when the key is in the cranking position...

the "R" terminal hooks up to a wire that goes to the positive side of the ign coil...    on gm cars and trucks with points as factory installation... the ignition switch breaks the connection to power the coil when the switch is in the cranking position...   when the starter is turning..  the R terminal contacts the contact disc and sends full battery voltage to the ignition coil positive side... to get a hotter spark during cranking...    

copy and past this link ... it is the wiring diagram for a 72 A body...

http://repairguide.autozone.com/znetrgs/repair_guide_content/en_us/images/0900c152/80/05/18/83/large/0900c15280051883.gif  

wow.. that wiring diagram is actually wrong where the starter wires hook up too....

that might be your problem if you followed that...

purple wire goes to the S terminal...
yellow wire goes to the R terminal

battery cable... and red wires go to the top post on the starter...    there are fuseable links in there to protect the harness from totally burning if there is a short sometime in the future...

here is a later wiring diagram that shows the hei wiring also...

http://repairguide.autozone.com/znetrgs/repair_guide_content/en_us/images/0900c152/80/05/18/91/large/0900c15280051891.gif
or PM me... i will draw it out and email you with a diagram... drawn by me...  

Great, thats what I was looking for. I'll check all the wiring and make sure everything is done right. Thanks