The crank I posted a link to is not a factory crank, it is the one I made from a bar of standard 3/4" x 36" round stock from a metal supplier. A bar size of .690" would be a special made size, GM often had material made to their specs rather than use a standard off the shelf materials. Obviously if you have a stock bracket and it is 3/4" it would be way to tight.
The search for an original crank can be frustrating and expensive, the crank I posted the link to is an inexpensive alternative, not an attempt to make a carbon copy of the factory crank. Very few people would notice that it's not the stock crank when they took my seat out of the truck, cleared the dust away to inspect what was in my toolbox. The 3/4" round stock fits the damper just fine and I use it often when setting timing or valves. How it would work to actually had start the engine, I don't know, I don't have the bales to try it.
And speaking of hand cranking, here's a guy that is looking for a broken arm:
On the other hand, here's a guy that came to the Stovebolt back in '08 and showed us a very nice restoration and a very nice video showing a hand start, only to be ostracized by some here as being a fake and using the incorrect method of grasping his crank. I applaud him for building a well tuned engine, he left abruptly in 2010, I wish he'd give us another try. I'd like to see how that '41 turned out.
I wonder how many of those naysayers have ever attempted a hand start of their inline six, or if they even had an inline six to start with.
