Hey guys got a little crank problem, I installed new main bearings using jegs assembly lube. torqued everything to spec. When I try to turn the crank it wont turn, if i use a wrench on the pulley bolt it will break over and spin by hand. but if you let it stop you have to use the wrench again to get it spinning. What gives? crank is cut.010" thats what is was when i tore it down and it spun good then. Went back with new .010" bearings now this issue
Flathead crankshaft issue
- Thread starter TexasT
- Start date
Frank Miller
Well-known member
Needs to come apart. Check to make sure bearing shells are in tight and there is no dirt behind them. Measure each journal with plastigage to check clearance. If you loosen one at a time you may find the problem bearing. With no rods or pistons the crank should turn easy. Unless the rope seal in the rear is dragging.
i found similar posts on here about it being normal. I have built plenty of wont say no brands engines I have never seen a crank do this. Everything is right on been plastigaged and all. Everything is in spec. The puzzle is why can you turn it by hand wants you get it to spin
quickchange34
Well-known member
The rear seal is causing the problem. It holds the crank when its new. I hope you put a little oil on it with your finger when you installed it. You will be fine. If it makes you feel better take the rear seal out and retork the crank, without the real seal holding it you can spin it by hand. Good luck.
One at a time, back-off the torqued studs/bolts to see if any one main cap makes any difference to the force required to spin the crank. If no difference, after loosening and retightening, one at a time, it is probably the seal. If there is a difference the assembly is showing signs of improper crank grind or main saddles that need to be align honed.