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Discussion Starter · #1 ·
Guys,

I am having trouble with my rebuild. Whats happening is once I torque the rod cap nuts to spec the crank wont turn. Well originally I had thought that the problem was with the front two rod caps having a clearane problem with eachother or that the rod caps themselfs were not facing the correct way. Today I removed all the rod caps except for just one of them in the middle of the motor which was torqued to spec. Well with jist ONE rod cap bolted on the crank still wont turn. The crank will turn all day long with all the connecting rods installed fingure tight but not if the nuts are torqued to spec. I messured the diameter of the rod journals and all of them are within spec and I am using standard sized bearings.

So what is wrong here? What am I doing wrong? Is there a specific pattern that the nuts have to be torqued? The crank had about 80k miles on it and ran fine when pulled out of the engine it came from. Any and all help is greatly appreciated.

Shane
 

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Maybe you have the wrong bearings on the rods? I don't know what else it could be, and yea, I think there is a specific tightening sequence for those.

Jay
 

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Discussion Starter · #4 ·
dode said:
I have one word for you

plastigage
I have never used the stuff before, could you enlighten me on how to use it.

Shane
 

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Cut a piece and put it in across the width of the journal...install cap and torque down without rotating...unbolt and remove cap and use package to measure.
 

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Discussion Starter · #6 ·
Ok, So once I do that and say for example the journals are within spec what do I do? Likewise if they are not within spec what do I do then?

Shane
 

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Do you have the heads on? If so are the sparkplugs in? When the rod bolts are torqued there is significantly more friction with all of those bearings, main cap bearings and piston rings. Can you turn it at all? Does it move any if you force it? If any of this is insulting I apologize, its just helpful with all of the background info.
 

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Discussion Starter · #9 ·
teal944.6 said:
Do you have the heads on? If so are the sparkplugs in? When the rod bolts are torqued there is significantly more friction with all of those bearings, main cap bearings and piston rings. Can you turn it at all? Does it move any if you force it? If any of this is insulting I apologize, its just helpful with all of the background info.
No, not insulting at all. The heads are on it but no spark plugs. It would turn over at all, I can litterally lift all of my 220lbs off the ground when trying to turn the crank over. Keep in mind its the same if just one rod is bolted to the crank or if all eight are.

Shane
 

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Did the crank come out of the engine your putting it in?
Did you have any machining done to it?
If it's from a different engine it could be warped to that block, running 'fine' in it, but siezing up in yours. Have you done run-out testing on the crank?

Just some areas to concider. I've rebuilt a 2.3 on my own before but I'm still no expert.
 

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Ok, did you lube all the parts prior to assembly? And the crank will turn freely without any rods attached, and when the rods are not torqued it will turn?

Did the pistons pose any trouble sliding in the bores?

What I would recommend would be to take all of the pistons/rods out. Make sure the crank spins freely. Then start with the #1 piston, install it and torque it to spec, make sure it spins, then the #2 and so on and so forth until they are either all in or you find where the bind is.

What Way are you trying to spin the engine? Im sure all the engine builders on here will chime in and tell me im a retard for telling you to try to spin it the opposite direction just to see if you can get it to rotate.

From my experience, a fresh rebuild is VERY stiff to rotate before it is first started.

Oh one other thing that comes to mind, Have you checked PTV yet? If your heads are on it may be worth taking them off until you get this ironed out. Recheck your timing if you dont want to pull the heads. I think its something simple that is just getting overlooked.
 

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Discussion Starter · #12 ·
People on the carrol are convinced that I have the wrong connecting rods in the wrong holes. I guess they are numbered and go in specific places. I will have to tear the heads off of it tomorrow and match all the rods up with the caps and put them in the correct cylinders. They say it should turn over after that.

Shane
 

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Yes they are numbered and it is important. I had a feeling it was something simple like that. It sucks you have to tear it all down. Good luck and keep us informed.
 

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yea they should go in a certain order and please get some plastigauge for reference on clearence, or I'm sure everyone is going to be reading something like this after the motor is done "it ran and than I spun a bearing?" plastigauge is cheap insurance!
 

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Not only is it important that each cap stay with it's rod, but the numbers refer to location and should be readable whenthe engine is upside down on the stand. In other words, number side down towards ground installed.

Caps are final fitted to a specific rod. Mixing caps is a sure fire way to lock it up as the holes that are formed by the cap and ropd are not necessarily aligned and round any more.

Get some plastigage as others mention, and a good book on overhauling your engine would be well worth the bucks.

Also, make sure you are in fact using std. bearings on a std. crank. If any doubt at all, take them with you to a machine shop and have them miced and checked against specs. A bearing for a ground crank will be thicker than a std bearing. A

Lastly, make sure the rods and caps are dry and clean where the bearing shell sets, and that the bearing is dry on back and that tab is in notch. Only swipe a bit of oil on face of bearing as you install against crank journal.
 

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First of all, plastigage is probably a good idea right now. It isn't expensive and will give you a good place to start. My guess would be that they gave you bearings for a crank that has been turned so you have no clearance when the caps are torqued down. If you check it with plastigage and it is good, then my next guess would be that some of the rods are on backwards. If you look at the journals on the rod, one side of it will be flat and the other side will have a bevel on it. Each journal on the crank has 2 rods on it, and you need the bevel on the front rod to face forward and the bevel on the rear rod to face rearward, if that makes sense. Basically on every journal, make sure that the flat sides are to each other. If that is correct, and your clearances are good, then maybe your crank is out of round. The only way to check this is with a micrometer, so if you don't have one you will have to have a machine shop check it for you. Oh yeah, also check the oil holes in the rod journals to make sure they are chamfered. If there is an edge/point sticking up on that hole, it will dig into the bearing and lock up the motor. If none of this helps, then post some pics of the motor as it is being assembled and we'll see if we can figure out what is going wrong. Good luck.

Mike
 

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wait , the cap issue is a good thing to bringup, for which rod goes in what hole though come on, that doesnt matter. that is a uniform size, i would look at bearing clearances and make sure you have the right size. and did you replace the rod bolts? they have to be pretorqued and the rods resized to make sure the bearing bore is still correct.
 

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Rod clearance

Stock rods or aftermarket? Stock rods are cracked from the factory so the rod and cap only allign one way. Definitely an issue if you have the wrong caps on the wrong rods. Aftermarket are also rod/cap specific and need to be installed correctly but they are machined and doweled. With the wrong caps on the rods you don't have round rod journals. Also, which crank? The rods are installed a certian way to offset the bearings to cnear the radius on the crank pin (outer edges of the crank pin). If the rods are installed backwards the outer edgs of the rod bearings can interfere with the radiuses and lock the engine up. This will also cause no clearance between the rods.
 

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sounds like some rods are backwards or the pistons? they are numbered and have to face a certain way, and yes use assembly lube.

when i was blue printing a 4.3L v6 i put the pistons in backwards and could not turn the crank for the life of me. ended up being the crank main caps on the wrong direction as well as the piston and rods.
 
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