Problem with a new crank
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Elder User
Joined: Feb 2004
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From: Fort Rucker, AL
Problem with a new crank
Bought a new crank and following the manual to the "t" but when I start putting the pistons in and tighten the rod caps I can't turn the crank. Is this normal because everything is new or am I doing something wrong? Need some help.
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Joined: Dec 2002
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From: Omaha USA
I would double check the bearings you have and make sure they not for a crank that has been turned more. Also , I use Plastigauge to check your tolerances. Its easy and you can get it at autozone , etc.. Just put a small piece of it on your crank, torque it down, take the cap back off and use the gauge they give you to measure how much it smashed the piece of plastiguage. I dont remember the tolerences for the rod but someone else will probably chime in. I think it was like .004-.008 but Im not for certain.
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Joined: Aug 2001
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From: Evanston, WY
If the crank turned fine before installing the rod caps then it is a problem with one of the following 3 things:
1. Rod journals on the crank too big.
2. Rod big end journals too small
3. Bearings too thick.
You will need to do some precision measuring to figure out which it is. Plastigage will only confirm that something is wrong, but won't tell you where the problem is.
I am assuming a couple of things here. The first is that the pistons slide freely in the bore. Second, that you are using a wrench or some other lever to try to turn the crank. If this is the case then you do have a serious problem that needs to be resolved.
-Scouder
1. Rod journals on the crank too big.
2. Rod big end journals too small
3. Bearings too thick.
You will need to do some precision measuring to figure out which it is. Plastigage will only confirm that something is wrong, but won't tell you where the problem is.
I am assuming a couple of things here. The first is that the pistons slide freely in the bore. Second, that you are using a wrench or some other lever to try to turn the crank. If this is the case then you do have a serious problem that needs to be resolved.
-Scouder
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Elder User
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From: Fort Rucker, AL
You're not going to believe this. When I took this engine apart I marked the caps with the piston. It was so dirty that I didn't see the factory numbers. No problem except that I have duplicates of the same number and nothing numbers over 4. Now what?
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From: Fort Rucker, AL
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From: Fort Rucker, AL
We are tracking now. The only thing I can do is make sure the clearance is there between the connecting rod and journal and that the oil groove is pointing the right direction. This is a nightmare.
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Lead Driver
Joined: Jan 2003
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From: Ohio
Mis-matching of caps will not be a good thing. I dont know if I would continue or not. The only thing that will make it right is to have each big end resized. They will take a couple thousands off each rod big end then rehone it to size. This will guarantee a perfect circle. If may be okay, it might not.
I would definitely do some re-thinking before I button it up for good.
Larry
I would definitely do some re-thinking before I button it up for good.
Larry
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From: Fort Rucker, AL
I didn't mixmatch the rods and caps but when I torque one particular rod down, it binds up the crank. For arguments sake I put that particular piston in several different cylinders and it does the same thing. I am taking that one piston/rod to a machine shop today. I think I have a bad rod cap.
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Elder User
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From: Fort Rucker, AL
The problem was that I had 2 that were marked 4. I took the pistons to a machine shop and he helped me with the rod caps by lining up the machined edge on the caps and the rods. Also the bearing line on the inside had to match up. I'm not thinking in thousandths of inches but I've quickly learned to. Alls well. The engine is buttoned up and it's smooth. Will put it back in "Baby" tommorrow. Thanks for all the help. Really. Thanks.
