We are rebuilding my nephews 340 and I’m not sure about the crankshaft drag. The book says it should turn by hand with the neoprene rear main seal. After all the caps were torqued to specs the crank will turn by hand but only after it is started by rotating it with a ratchet on the damper bolt. If it sets for a little while it can not spin it until you start it with the ratchet again. It doesn’t feel like it anything is binding but it is snug. Any help would be appreciated. Thanks………..

Sounds like it's a bit too tight...line hone time

If it spins easily with a ratchet then you should be fine. Depending what you used for assembly lube and how much you used will affect the drag.

how is it without the seal?

Will it turn by hand if you grab the coutner weights?

Pull a main cap and look for wear on the bearings.

did you use plastigage to check clearances? You can pick it up at any parts store, cheap. Check end play at the snout too.

id say its tight. ive only done a few engines but they all turned nicely with just the crank in (lubed of course).

if you didnt check the clearances, you better

Check end play and bearing clearances. Did you set the thrust bearing correctly?

Sheldon

With no pistons or rods in there it should turn very easily even with the rubber seal in the rear main. Is it consistent through the rotation or is it tight only in certain spots? I'd start by checking with plasti gauge. Run out and end play should also be checked.

If the end play isn't correct, how do you fix it?

when my 383 was getting done at the machine shop, I stopped by to give them some cash and he showed me where they were on it. Crank, bearings, and rear seal were in. He gave it a spin by hand with the counterweights and it probably spun 1 1/2 turns after he let go! I expect this one to make some good power!

Sounds like it is too tight. Check end play, bearing clearances, check crank for straightness, and check the alignment of the main bearing bores.

I'd R&R the crank/bearings clean the saddles & align the thrust bearing halves & oil the journals. If there's still a problem I'd have your machine shop mike everything otherwise there will be an early failure down the line.

if it were me I would ask someone like Dram for answers or post this in the race section.
Pete