Hotrod Lincoln gave you the information you need. Taking all plugs out would make it easier to turn over bringing the next cylinder to TDC. Wouldn't hurt to disconnect coil, nothing wrong with an extra level of safety, but if ignition is off you shouldn't get any spark. I'm not sure what's dangerous about it. It can be dangerous on an airplane engine as there is a large prop on the front and it can swing on you if you're helper isn't careful to hold it at TDC.


1953 Canadian GMC 9314 w/ (factory) Chevy 235