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New Bearings Crank wont turn?


182kartracer
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So i am rebuilding a 83 320i engine to put into my car. I currently just installed new main bearings, con rod bearings, and new seals at either ends of the crank along with new piston rings. I have all of that installed. When i torque down the main bearings the crank still rotates but when i torques down the con rods it slowly gets harder and harder to turn. I can torque down all the bolts and it still turns but if i wait 5 minutes and try again it's like the thing is seized. I have applied generous amounts of assembly oil while putting it together. Also i checked the clearance of the bearings and they are .025mm I know that is a bit on the tight side but i wouldn't expect it to lock it up. Any advice for things to check would be greatly appreciated.

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If you mix conrod shells (the part that comes off) between rods, this will happen.  Each rod is matched to its shell.

 

I did it once by mistake.  And then had to figure it out by trial and error.  

 

Also, with tolerances that tight, ANY amount of foreign material in the rods will make it stop turning...

 

t

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Have you assembly-lubed your bearing shells during assembly? Also, double check the rod caps for correct orientation.

 

If I remember right, I think the numbers on the rod caps have to be on the same sides.  You can't flip the caps around opposite the way they were, with numbers on opposite sides. Then it won't spin very easily.   It's easy to flip them around if you're not paying attention, because it doesn't really look like it would matter.

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....but 2002 rod caps don't have numbers on them, unless the engine's been apart and someone has marked them...

 

t

 Mine had engraved numbers on them, and it was the original engine with three bolt oil pump sprocket and no evidence of a rebuild.

 

He's got a 320i engine though, heh.

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....but 2002 rod caps don't have numbers on them, unless the engine's been apart and someone has marked them...

t

Toby- all three. m10 engines I have torn down have the cylinder numbers stamped into the rod and rod cap. Blue book shows them as well.

Numbers point in a certain direction for the oil hole on the little end.

Edited by jgerock
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The rods and caps are marked 1 2 3 4. The oiling hole in the rod which feeds the wrist pin bushing faces towards the front of the block. The numbers on the rods and caps should be on the same side. Or, the tangs on the bearing shells should be opposite each other in the off chance there are no stamped numbers.

A suggestion might be to install caps one by one and turn crank over after each cap is torqued. Does one cap make it tighter?

As parts are added, bearings, pistons with rings, etc you are adding more friction points. How tight does it get?

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