F-20 Connecting Rods

Can anyone tell me the original thickness of the shim stack and what the original diameter of the bearing end of the connecting rod is? My connecting rods and caps have been filed and I want to get the bearing bore back to OEM specs. Thanks
 
The problem is that as the babbitt wears, the shims are removed to take up the wear. So, you would have to find a tractor with a NEW bearing and all the factory shims intact to measure. Tough call. Many years ago I looked into having my old bearing shells re-babitted. The cost was around $500 for a set of 4. Most of that was for the guy to create the fixture. I would then have to source new shims.
 
Do you have a new crank you are trying to fit? I don't understand the problem. If you had all new parts I suppose there was a set number of shims that would be installed at the factory. But you don't have all new parts do you? I have a question of my own I was just trying to find an answer for. I am cleaning up a set of bearings and I think they may be oversize but I can't find the number and I'm away from my books.
 
My old Federal Mogul bearing manual say each rod brg. requires a shim pack of which is made up of 4-.050 shim and 2- .031 shim laminated. That would give you .131 on each rod bolt.
 
From my memory, it was closer to 3/8" to 1/2". My 1929 Regular has a recently-replaced bearing in it, with a full shim package. It's in the engine now, so I can't measure it.
 
you just need to get the original crank spec's and then resize the rods accordingly with out the shims. did that on wk40 rods and justleave the shims out. totally not nessesary.
 
Filed is what I meant. This causes the rod bearing to have too much crush as the shims contact the bearings and not just the rod. This is why I want to know the original diameter. If I can hone the rod to the correct diameter with the original amount of shims installed, I will have the correct bearing crush. Then I can remove shims and keep the correct bearing crush. The bearings have not been altered.
 
(quoted from post at 17:38:57 03/01/13) Filed is what I meant. This causes the rod bearing to have too much crush as the shims contact the bearings and not just the rod. This is why I want to know the original diameter. If I can hone the rod to the correct diameter with the original amount of shims installed, I will have the correct bearing crush. Then I can remove shims and keep the correct bearing crush. The bearings have not been altered.

Bearing crush? on a babbit bearing? Oem procedure is to install the rod on the crank with a full shim pack,It will most likely be loose, remove one shim from each side retighten the bolts and check for tightness/ drag. Continue removing shim sets one at a time until the rod is tight to move. Then install one pair of shims back in and tighten the bolts and install the cotters, thats it. Works best to do this with the rods pointing down instead of in the cylinders. I find usually once I get the first one the other three
will be very similar in the number of shims needed. The shims do indeed contact the shells of the bearing they are made that way to keep the shells in place and so they don't rotate in the rod.
 
Bearing crush? on a babbit bearing?

Yes, F20 con rod bearings are replaceable insert bearings. Brass backed with babbitt wear surface.

Bruce, while I don't know the figure you are looking for, it can be calculated. You have the rod cap which is an arc of the original circle. Using the width and height of the arc, the diameter of the circle it came from can be calculated.

Another option is to file the ends of the bearing insert until it matches the rod cap. I had to do that to one replacement bearing insert on the 10-20 I am rebuilding. Remember it is a low speed engine and very forgiving. When I got my 22-36, I checked it's rod bearings and removed shims to tighten clearances. I measured the crankshaft journals while I had it apart and found them to be .005-.010 out of round. I just removed as much shims as I could that still allowed the engine to rotate freely. It runs just fine and does not knock.
 
(quoted from post at 20:43:10 03/01/13)
Bearing crush? on a babbit bearing?

Yes, F20 con rod bearings are replaceable insert bearings. Brass backed with babbitt wear surface.

Kirk, while the inserts are somewhat similar to the more modern bearings, the fact they have adjusting shims makes them different and I don't think crush applies like it does on a thin insert. They fit into the rod with a slight interference fit and the thick heavy shell and shims hold them in place. The force necessary to crush them like a modern rod and insert would be huge. Not sure the existing components could take it.
 


I guess I misunderstood your previous post. There should be just a small amount of bearing crush, just enough to hold the insert in place without any looseness, but not near what is needed on a modern insert bearing, on that I agree.
 
I don't think so. If material has been removed from the rods removing more material won't put it back to original. What you need is another set of rods.
 
dont forget to use plastigauge when you are re-assembling



also, torque and check rods caps at both the 12'o clock and 3 or 6' o clock position. ive found that over the years many are just slightly out of round. it may fit fine in one spot but be a touch tighter in the other. do the math and split the difference
 

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