New bearings, difficult to rotate the crankshaft.

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Djakken

Djakken

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I have changed</SPAN> bearings and pistons in my 273. The problem is that it is difficult to obtain the crankshaft to move. Could it be enough to prime the oil system, or do I need to open the engine again? The latter option I'd prefer to avoid. All the bolts has been tightened to proper torque, so that is not the fault.</SPAN>
 
Are the pistons and rods in the block or is it just the crank? Was the crank easy to turn in the block with out the rods and pistons?
 
The pistons and rods are in the block. The problem arose when the rod bolts were tightened. Before that I tested the breakaway torque of the crank, and it was within spec.
 
since you stated you dont want to open it again I have to assume all the rods are in and the pan is on. A freshly built bottom end should turn by hand with some degree of difficulty. Can anyone reading your post say if you assembly is too tight ? I dont think so.
You need a experienced engine builder to lay hands upon it before you proceed.
 
Tear it back apart and plastigage it . Be safe not sorry. Checking the ring end gap is also a must.
 
plastigauge. check the main and rod bearings for clearances. can someone post the specs. is it .0025 to .003 mains / .0025 to .003 rods?

DJakken it sounds like one of your rod bearings are too tight. it could be one of the rod caps isnt the original that was on that particular rod. you can check the clearances but i'm guessing one or two of them has .000 clearance

the bad news is you have to take it apart or you will ruin it. the good news is that it will be done right

you may need to take all of the rods/ rod bolts / caps and get them checked by a machinist
 
moparlover said:
plastigauge. check the main and rod bearings for clearances. can someone post the specs. is it .0025 to .003 mains / .0025 to .003 rods?

DJakken it sounds like one of your rod bearings are too tight. it could be one of the rod caps isnt the original that was on that particular rod. you can check the clearances but i'm guessing one or two of them has .000 clearance

the bad news is you have to take it apart or you will ruin it. the good news is that it will be done right

you may need to take all of the rods/ rod bolts / caps and get them checked by a machinist
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don`t know about 318`s, but is it possible that the rod bearings have a chamfred side-and you have them turned the wrong way?:eek:ops:
 
I'm pretty sure I've put all rod bearings right. An error may have been that there is oil on the back of the bearings. Guess I was over-ambitious with oil, "too much can never be wrong."
 
well you can check them with plastigauge... without removing the pistons. just remove each cap and check that side only at first. put plastigauge, retorque, remove the cap and see the width. you will find out which ones are binding.
 
Check your rod bearings if they are stamped .010 or similar - maybe they are made for undersize journal and therefore too small for your application!

I´d check all the clearances.

Michael
 
Djakken said:
The pistons and rods are in the block. The problem arose when the rod bolts were tightened. Before that I tested the breakaway torque of the crank, and it was within spec.
Click to expand...

did you put the rod caps on right and on the corresponding rods they came from?

if not...the they will be hard to turn and if it starts...thy will fly through ur oil pan too.lol
 
Remove your rod caps one at a time and turn the engine over each time you take one loose.That will help you determine which one is the problem(if it is only one). When re-assembling a motor you should rotate the assembly each time you put a bearing in and then if its tight you will know which one is tight.Oil on the back of your bearings will not cause your engine to turn over hard. The oil will squeeze out as you tighten it down. You have something solid binding up. Is the engine in the car and does it have spark plugs in it? that will also make it harder to turn(but not That hard)
 
Oldmanmopar said:
Tear it back apart and plastigage it . Be safe not sorry. Checking the ring end gap is also a must.
Click to expand...

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"Checking the ring end gap is also a must"


Do you have a "feel" for how tight the pistons/ rings are in the bores? Are these used pistons? ANY CHANCE there is dirt/ carbon down in piston ring grooves?

NOW IS THE TIME. I'd pull the short block apart and start over.

Don't necessarily need to remove the crank. BUT Pull the main caps and plastigauge the crank, then MEASURE the turning torque of the crank. At this point you should EASILY be able to rotate the crank by hand by pulling on the crank throws.

Pull at least one top ring, and use the piston to "square" the ring in the bore, and measure the gap.

If there is ANY possibility that the ring grooves were not scraped clean, remove the rings and do so.

Then put ONE / piston in at a time, check with plastigauge, and then check the turning torque of the crank.

But above and beyond all this, WHAT IS the turning torque of the assembly? Saying that it's "too hard" or someone else saying "should be able to turn by hand" is pretty subjective. "Turn by hand" with WHAT? hanging onto a 1 foot bar? a 2 foot bar? a 6 ft bar?

MOST OF the turning torque in a new short block could very well be the rings.
 
Thanks guys!
I have put in new pistons and rings, no problems there.
Will follow hemichucks advise and remove the rod caps, one by one.
Should have done it directly, but "if it don't kill you, it makes you stronger".
I try to think on that when I take the motor apart, for second time the last month.
 
One problem with the one by one method.... If you have the rod caps switched around,,, what rods are wrong as a combination??? In other words, if one is bad, then at least two are bad.... Make sence???
The only way to confirm your rods are assembled correctly would be to mic them when torgued with a telescopic gauge or take them to a machine shop and they can check them for out of round.
If you have the patience, you can "as I do" place a bearing into each rod and main journal, measure the inside diameter, then measure the journals of the crank. You can play around with swapping bearings back and forth between caps and saddles untill you get the most common clearance between the bearings and there respective journals.
Might seem like over-kill, but I have the warm and fuzzy feeling when I'm done with my build!
 
In one way I am lucky. The rod caps are numbered, 1 to 8, the numbers also point out the right direction. Maybe I have made a mistake with one cap and switch it, but I don't think so. I Will check all mistake possible and follow your advises. As soon as I know the cause, I get back to you.
 
The rods have a bit of side clearance. You can simply try to jiggle each rod when they are torqued to see which one will not budge, then take that one apart and guage it. I think Sheppards book tells you to either wipe bearings with scotchbrite or scrape them with a knife to clearance them, perhaps that is the cam bearing? Better safe than sorry. Did you use assembly lube? A dry bearing is a cranky bearing...Also make sure you assembles the bearing in the part correctly. If you torqued down a bearing that is in backwards, the tang will have no where to go and compress against the crank, locking that one up.
 
This happened to me on my first ever build. One of the rod bearings got out of position and on top of the other half just a little. When I torqued them down that was it, the motor didn't turn.
 
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