QuestionWhich is the best indicator of correct bearing clearance, plastigage or ability to turn the crank when bearing caps are torqued? I am assembling a newly rebuilt engine. The main bearing clearances show .002" by plastigage, which is correct, but I can't budge the crank with a 10 inch bar across the flywheel flange bolts when the cap bolts are torqued to as little as 20 ft. lbs. The center bearing has flanges for end play control, and I have about .004" there.
AnswerI'm guessing you are asking about the main bearings, not the rods.
Assuming you are trying to turn the crank with nothing else connected to it (no timing chain or pistons installed), it should turn quite easily with around 10 foot pounds of torque applied to the front of the crankshaft.
Since it isn't that easy to turn, I suspect you have an out of round crankshaft or a bearing that isn't perfectly round - plasti-gauge only checks one location on the bearing - there must be another place on at least one bearing that is binding. The other possibility is that one or more of the main bearing caps is on backwards.
Unless this engine has been modified, the bearings were poured in place, then align bored in a special machine made for that purpose. Egge Machine company in Santa Fe Springs CA is one firm that does this. They will check the crankshaft for prefect roundness, and correct it if it has a flat spot, and then pour and size the bearings to fit it properly.
If I guessed wrong, and you are asking about the rod bearings, the story is pretty much the same, but perhaps one or more of the rod bearing caps is on backwards.
Dick
