starter/electrical issues

[14hatchie]

Ok guys/gals, I have pretty much finished wiring up my 71 k15 with the classic update date series for AAW. My problem is when I turn the ignition on they only way I can get the starter to stop engaging is to undo one of the battery terminals. I can turn the key to the off position but it still wants to turn over. I do have the battery grounded to the block and also the frame is grounded to the block, could this be the cause? This is the first time I have wired a vehicle so any help would be appreciated.