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Old 08-16-2012, 07:21 PM
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Crankshaft won't turn by hand

i'm in the process of rebuilding my sbc. i got the crankshaft in a torqued to spec and it spins freely. After i installed a connecting rod and piston i can't turn it at all as soon as i loosen the rod cap a lil bit it turns freely. i'm stumped on what could cause this. It is a reground crankshaft the came with matched bearings.

I also have a question on whats the best way to remove a new piston from a connecting rod?
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Old 08-16-2012, 07:27 PM
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You won't be able to turn it "by hand" But it should turn using a breaker bar. If you can't turn it then you have one or more caps on backward. When i built my current 350 i couldnt turn the crank after installing all the pistons but after i switched 2 caps around it spun freely. So thats another thing to try.
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Old 08-16-2012, 07:38 PM
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i know the caps are lined up in the right direction i may have got a couple of them mixed up though.
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Old 08-16-2012, 07:44 PM
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Tighten one cap, try to turn it, if it turns then loosen that cap back up and go to the next one and repeat. You'll find the one causing the problem.
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Old 08-16-2012, 07:54 PM
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please,buy some plasti guage and stop when you have the short block assembled,bag the motor and travel to the nearest reputable shop and have a guy visual check it all.take your balancer and bolt and torque wrench.
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Old 08-16-2012, 08:02 PM
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Quote:
Originally Posted by vinniekq2 View Post
please,buy some plasti guage and stop when you have the short block assembled,bag the motor and travel to the nearest reputable shop and have a guy visual check it all.take your balancer and bolt and torque wrench.
I agree, Plastigauge would be a good idea. Especially since the crank has been resized. Good call vinnie
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Old 08-16-2012, 08:09 PM
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i plastigaged it and it was a lil tight. i went and swapped the cap with the connecting rod paired on the same rod journal it spun fine. i'm gonna put the other connecting rod and piston in tomorrow and see if it causes me problems. If not thats what the problem was. I've got my grandpa helping me and he's built quite a few engines in his day funny thing is he never used plastigage on any of his he just tightened them down and made sure the rod didn't have any play by hand and spun over easy with a bar turning the crank.
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Old 08-16-2012, 08:36 PM
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After tightening the the bearings down, smack "ping" the cap with a hammer. This will usually set everything if something has gotten slightly misaligned and will loosen it up.
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Old 08-16-2012, 08:56 PM
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Did you mark the rods and caps when you removed them during teardown?
Did you have the rods resized?

If you didnt keep the rod caps with their original rods, then you should have all the rods resized so the bearing crush is correct and your clearences arent wrong. Bearings are not supposed to be "worn" in, if the clearences are too tight or too loose, you will have damage on startup.

Did you clean the crank after you got it back from the machine shop. Never trust that everything has been cleaned from the oil holes, some shops only blow the outside of the crank off, and leave shavings in the oil holes, expecting that the customer should know to clean the crank before installation.

Are you installing the rod/pistons in the right dirrection, they have markings to show which side should face the front of the motor.
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Old 08-16-2012, 09:03 PM
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i didn't mark them but i laid them out in order. i didn't have them resized. i'm not even sure if there is a place within a couple hours of here that resizes rods
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Old 08-16-2012, 09:16 PM
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DO NOT smack any rods with a steel hammer,lol. Is this a trial fit of the parts? an engine is usually fitted a couple times,crank hand polished, you will need to or should check side to side clearance on rods, piston to wall should be individually checked,,etc,,, is this in any way a high performance engine?crank end play,,,
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Old 08-16-2012, 09:29 PM
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i wouldn't say high performance. its just a mild motor for my mud truck only gonna be ran a few times a year.
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Old 08-16-2012, 09:44 PM
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make notes of all clearances as you build it. make it as perfect as you can afford,then go fling some mud
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Old 08-17-2012, 11:26 AM
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I also have a question about the pistons i'm using. I messed one up when i was putting it on the rod. So i ordered a new piston thats the same part number but where the wrist pin goes in it's different. The difference is that one has a full circle of raised material around it and the other only goes about 3/4's of the way around. Would this make a difference in the weight or will it run fine?
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Old 08-17-2012, 04:36 PM
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Quote:
Originally Posted by vinniekq2 View Post
DO NOT smack any rods with a steel hammer,lol.
I'm not saying use a 5 lb. beater but a small ball peen or dead blow.
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