Question - over tightening connecting rod caps

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Model T Ford Forum: Forum 2011: Question - over tightening connecting rod caps
Top of pagePrevious messageNext messageBottom of page Link to this message  By David Kriegel on Wednesday, December 07, 2011 - 03:08 pm:

I just installed new rings properly gaped in rehoned cylinders

The first two rod caps were installed then engine rotated (easily) to do the last two. They are installed Now engine is frozen Will barely move pistons with full arm power on crank I assume I have over torqued rod cap nuts However, I tightened them just enough to install split pins Any advice before I remove all the rod caps and start over? Thanks from cold Indiana (working outside under the car)


Top of pagePrevious messageNext messageBottom of page Link to this message  By joe bell on Wednesday, December 07, 2011 - 03:19 pm:

Are you sure you installed the caps the same way they came off? Get some plastic gauge from parts store and see where your at, if you marked the caps to the rods and kept them in the journals they came out of there should be no issues. If any thing you would need to remove shims. Hope this helps!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dean Yoder on Wednesday, December 07, 2011 - 03:30 pm:

David, Add a Shim on one side and see if this will loosen it up. You probably have two rod journals that are slightly larger. Adjust shim at a time . over torquing strips nuts and bolts.
siezing up is because of journal / rod bore too tight/size.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Wednesday, December 07, 2011 - 03:32 pm:

The only thing over tightening will do is strip the threads. When the nuts are tight, the cap is tight against the rod. You either have the cap backward, or not enough shims in one or more of the rods. If you back off all the nuts and then tighten them down one at a time, and rotate the crank, then back off that one and tighten the next one and rotate the crank, then do that with all 4, and the crank will turn with each one tightened individually, then tighten all 4. If when you are tightening individually, you find one too tight and it binds, try reversing the cap. If that fixes it, you have found the problem. If that makes it worse, the cap was on correctly before, and you need to add one small shim. It might be tight, but remember, you have new rings, with honed cylinders and tight rod bearings. If you don't have a starter, you might need to pull the car to start it the first time, but after running a while should loosen up and then you will be able to crank start it. Remember to torque the head bolts again after warming up the engine.
Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Allan Bennett on Wednesday, December 07, 2011 - 03:39 pm:

David,
I'm with Joe. Nothing else should change given what you have done. Undo the two offending rods and tighten them one at a time. This should indicate which is the problem. Switch the cap around and see if that cures the problem. If not, perhaps you lost a shim when disassembling and you will need to resort to some plastigage to find the corrrect clearance on the offfending rod.

Hope this helps

Allan from down under


Top of pagePrevious messageNext messageBottom of page Link to this message  By Brian Holcomb on Wednesday, December 07, 2011 - 07:31 pm:

Did you mistakenly mix up the rods from one cylinder to the another? I know that the rod journals in my '26 are not the same dimension.
Farmer Fred decided that it was only necessary to grind the journals on 1 & 4 and leave 2 and 3 standard!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bill Dugger on Wednesday, December 07, 2011 - 08:18 pm:

From what I remember the rods and caps on my two engines had either file marks or numbers stamped on the rods. That is another thing to check. Just my opinion. If there is 1 file mark=1, 2 file marks =#2 etc, or 1 2 3 4

Bill D


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bill Dugger on Wednesday, December 07, 2011 - 08:21 pm:

I also meant to add that the caps must have the marks ir number on the same side 1
2
2 etc 1


Top of pagePrevious messageNext messageBottom of page Link to this message  By Richard Gould on Wednesday, December 07, 2011 - 08:42 pm:

I'm with Joe. I've done it on mains. Got the marks confused. Once you've done it, you'll never do it again.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ted Dumas on Wednesday, December 07, 2011 - 10:14 pm:

You need to use Prussian blue and fit the journals. You may have reversed the caps or swapped them from one rod to another. If you have the right rod and the right cap in the correct position, it should fit as before and show a near complete bearing with the Prussian blue. Plastigage will check the clearance at one point but will not tell you how the bearing fits the crank.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kohnke Rebabbitting on Thursday, December 08, 2011 - 01:21 am:

Bluing will tell you nothing, in your case. If you are not sure if the cap is on right, look at the inside of the cap, and rod, many times a rebuilder will not center, or don't know how the center the rod, so you have the same babbitt thickness, on both sides of the rod, one side may be thicker then the other, so you can match. The problem with checking file marks, or any other marks, there is a large builder that sells to some venders, and when they take a rod apart to rebuild, the caps all go in one place, and the rod parts go in another, and when they put the rod together, none will ever see their mated cap again, so the marks can be useless, depends who you got them from. If you know you got your cap on right, measure your shims, and add to the thinnest pile, by .002, if it is tight, add to the thinest pile again, just try to keep the sides even. If by adding a .002 shim makes it to loose, take out the .002, and try a .001 thousandths. If that is to tight, you know which to go. The rods should be pulled to 30 foot pounds, and then line up the key, and Never Back a Nut off to do that. Herm.


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