Mixed up Connecting Rods

MFJohn · Feb 16, 2017

When replacing a rear main seal on a Continental 260 4 cylinder engine, I noticed that the #3 connecting rod was in the #2 position, and the #2 connecting rod was in the #3 position. The connecting rod bearing caps were in their correct position. Obviously, a previous owner screwed up the assembly. I bought the tractor a while ago and have only run it a few minutes, long enough to discover the rear main seal leak (oil pressure was OK, 15-20 psi).

Question: Would you put the connecting rods back in their correct position, or leave well enough alone? (I think I could swap them from below, without pulling the head.) I suppose I could inspect the bearings to see if there's abnormal wear.

Bob Harvey · Feb 16, 2017

The old song " if it ain't broke why fix it" Likely OK - no warranty given or implied. HTH

showcrop · Feb 16, 2017

An engine that I have apart right now, has two separate 1-4 numbering on the rods.

Adirondack case guy · Feb 16, 2017

Last winter I rebuilt a 1969 Case 930, with 401cu.in engine. When I got it torn down because of cracked heads letting coolant into pan, I found two later 70 series rods in the engine which weighed nearly 20 grams more than the other 4 original rods. Fortunately I had an older 1964 930 salvage tractor with the older styled rods. The machine shop used two of the six salvaged rods which were closest to the weight of the original four and I installed them. The numbers on the rods in this now 426cu.in. engine are all miss numbered, and duplicate numbers but it purrs like a kitten.
Loren

Ozlander · Feb 16, 2017

I think the right cap on the right rod is all you need to worry about.
I'd run it like it is.

Mike(NEOhio) · Feb 16, 2017

Who knows how long it's been that way. Probably well worn in now. Leave it alone. If you ever rebuild it put it right.

JMOR · Feb 16, 2017

I'm ridin with Ozlander & Mike.

rustred · Feb 16, 2017

you have nothing to worry about now.they are just numbers. the important thing is that both halves must match.and if putting the same brgs back they must go to the proper journal it came from. but if the rods are getting resized # mix up dont matter, but its not normal to mix them .
you talking about swapping from below , i dont see how that can even be done. leave as is.

Duner Wi · Feb 16, 2017

I would prefer rods be in the correct holes. If you do switch rods and caps to corresponding rods and the caps. To be safe I would take the rods to a machine shops and get them resized.

Goose · Feb 16, 2017

I second that. The important thing is that the rods have the proper caps on them.

Steve@Advance · Feb 16, 2017

As long as the caps are on the correct rods there shouldn't be a problem.

I would take a good look at the 2 rods, up top where the wrist pin goes through. Some rods are off set slightly, front to back, mirror image. If they are off set, and installed wrong, the rod will bind against the inside of the piston and against the side of the crank journal. You can compare them with the ones installed correctly.

MFJohn · Feb 16, 2017

To be clearer - The #2 piston has #3 rod and #2 cap. #3 piston has #2 rod and #3 cap. I'll switch the caps and call it good, unless the bearings are shot. Thanks for the feedback.

mite-help · Feb 16, 2017

''to be clearer'' now that really throws up the red flag. with that & oil leak for unknown reasons, I would be real 'skeerd'

jm. · Feb 16, 2017

Those old engines are pretty forgiving. I sure would not go to pulling the rods, think you will be OK doing as you said.

Bob · Feb 16, 2017

There's no telling what mite have been done previously, rods could have even previously been resized with non-matching number caps. If you choose to mess with it at all, take the rods and caps to an automotive machine shop and have them checked and the caps swapped and/or the rods "resized" as needed.

David G · Feb 16, 2017

I would leave well enough alone if rods and caps matched, in theory it should make no difference if bearings and journals are sized the same.

David G · Feb 16, 2017

I read further below that the caps and rods are mismatched.

You are "probably" OK if they do not bind, but If me, I would pull all and take to machine shop and get resized.

Gary Mitchell · Feb 17, 2017

Same here. gm

MFJohn · Feb 17, 2017

The rods are centered on the piston pins for both cylinders, so I'll leave the rods where they are and only swap the caps.
On a MF35 (Z134) that I previously worked on, the rods were offset like you described.
Thanks.

travis miranowski · Feb 17, 2017

It took me a while to figure out if you meant, but I think you are saying you have #2 rod with #3 cap?? If so I would be worried. Only two possibilities here, they did a quick bearing change or overhaul and mixed up the caps or they took the rods to the machine shop and they mixed up the caps but trued up the rods anyway which I have seen and is OK as long as the rod is true. If the latter is true then switching the caps back is big trouble. If it were me I would remove the rods and have them looked at but if that is not a possibility then I would just leave it alone and hope for the best.

dr sportster · Feb 18, 2017

Your probably not going to do that without pulling the head and you don't have enough info to start swapping parts around.

Mixed up Connecting Rods

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