Did you have the crank completely out or just loosen all the bearing caps?
The service manual says that the rope seal needs to be mashed into the groove with a dowel starting at the center and working towards the parting line of the cap. If you don't have it all the way in, the crank will bind up.
Kevin 1951 Chevy 3100 work truck Follow this saga in Project Journal Photos 1929 Ford pickup restored from the ground up. | 1929 Ford Special Coupe (First car) Busting rust since the mid-60's If you're smart enough to take it apart, you darn well better be smart enough to put it back together.
I'm actually putting together a 54 235. I just installed the Best Gasket (4519S) rope seal to their specs and rolled it as Klhansen mentioned, last week. Crank, bearings, caps, all installed and shimmed for .002/.003" clearance on all mains, had no problems with crank spinning. I did a bit of research on the main seals and watched a few YouTube vids with them being replaced with the Best Brand design and great success.
Does your motor require shims on the mains? I believe early 55's still require them, if not all of 55.
Did you test fit the crank/bearings prior to installing the main seal? I did this first, to set bearing clearance, then installed and oiled the seal per instructions.
Are # 2 and 3 caps installed and facing proper direction? The caps are labeled F and R for direction.
Here is a video I watched as a reference. I'd think the process is pretty standard among vintage motors.