Farmall Cub

I have been working on a 49 Cub. It was running fairly well and just quit. It would not turn over with the starter or hand crank. I have begun to tear the engine down and found the connecting rods are over torqued. Not 16 pounds the book calls for more like 40 0r 50. I also found the pistons in the wrong cylinders. No. 4 in No.1, No. 2 in No. 4, No. 3 in No 2, and No. 1 in 3. The bearings and crankshaft look good so far. When running it had over 50 lbs. of oil pressure. My question is could I replaced the bearings and rings without major machine work. There may be a main bearing bad that I haven't gotten to. What does installing the wrong piston on the wrong journal do?

rods are 16 lbs, mains are 45 lbs, measure the bore for size, needs 4-5 thou for clearance, check ring gap to tight and it can lock up when it gets hot, rods have #s for the cylinder they go to and #s should face cam, plastic gauge the bearings to see the clearance, should be .002-.003

I will say what I think based on how I understand engines and building and tolerances. I am not saying this as an expert or an engine builder.

You oil pressure as you know is good. Sounds like your rods are over torqued, but all this would do is possibly deform the bearings too much and create odd wear points if it messed with the clearances. It would still run but "self clearance " itself if actually touching anywhere. This isn't a good thing just saying what may happen. Pistons and rods would be numbered for the cylinder they came out of, but I believe these would all be mass produced parts and it wouldn't matter where you installed a rod or piston. For example if you bought used pistons or a used piston to replace a bad one you would just buy a piston not a #3 piston or whatever for example. If your disassembling an engine you stamp the caps and all the pistons and rod assemblies to keep them all the same hole they came out of.

If it was me I'd replace all the rod bolts since they are over stretched possibly at worst. But I probably would be tempted to re assemble as it with new bearings. It was only 40# not like 95#. While too much those are quality fasteners. And if you need new rings replace those as well. Just check to make sure the ring gap is in spec. I don't see why any machine work would be needed for an engine that was running...assuming when you measure everything it's within spec. Like cylinder bore size and if there round, look at the rod and main journals on crank, and look at piston condition.

Again, I am not an expert, read all you can listen to what people say and make the best decision based on what your comfortable doing and fits your budget.

I didn't think about the rod bolts being stretched. I did not smoke and had 100lbs compression. I will replace the bearing and rings, checks the clearances and put it back together. Where would I find rod bolts and nuts?
Thanks for all the advice.

Some engines have instructions on assembly of the rods/pistons to the cylinders due to the design of the engine. Example is a old model Willys/Jeep engines have the cylinders marked on the rods because they are designed that way for proper lubrication. While the pistons are the same the rods are not the same. The manual says that #1 and #3 rods can be interchanged and #2 and #4 rods can be interchanged because of the way the lubrication enters the rod. Not saying the the C60 engine has any such design features but it is still best practice to install the pistons into the cylinders that they came from/marked on the caps and rods.

Just why did you take it apart? i haven't seen anything you described that would call for a teardown.

Do you have the head off the engine? If yes, continue with the tear down. Then measure everything.

If no. I would plastigauge the rods and mains journals. Then determine what to do.

5 Forward wrote:I didn't think about the rod bolts being stretched. I did not smoke and had 100lbs compression. I will replace the bearing and rings, checks the clearances and put it back together. Where would I find rod bolts and nuts?
Thanks for all the advice.

Again I am not an expert, and am not even sure how these rods and bolts assemble. I don't know these things like others I'd have to go look at a picture of them to know. But like on Chevy small blocks you get rod bolts and nuts from parts places...anyone selling parts you could get them for SBC. For these engines again I am not sure of the design of them or the speed grade of the bolt if it is just a plain one? Not sure if they have to be installed with a press or just a slip fit? I would think a parts place would have them but again I am not sure. But my gut and me I would use it how I took it apart. There probably really good high strength steel and I doubt there is any damage to effect your parts at the difference of 16# and 45# of torque.

How did you conclude the rod bolts were over torqued?

It probably doesn't matter which bore each piston goes in but it's VERY important that each connecting rod goes back in the correct location.
Since you don't know anything about how this engine was assembled (it appears that whoever built the engine didn't pay any attention to details), I'd check all bearing clearances, and ring end gaps as others have said.

Connecting rod position shouldn't be a big deal. But keeping each rod cap paired up with the original rod is critical.

Jim Becker wrote:How did you conclude the rod bolts were over torqued?

Torque wrenches work in reverse or you can use the digital things that you put on your ratchet or digital torque wrench.

Clemsonfor wrote:

Jim Becker wrote:How did you conclude the rod bolts were over torqued?

Torque wrenches work in reverse or you can use the digital things that you put on your ratchet or digital torque wrench.

Yes, you can measure the torque required to break a nut loose. I doubt that once measured it tells you much about the torque applied years previously to tighten it.

I used a beam type torque wrench to loosen the remaining bolts. 30 to 40lbs. It took a lot of effort to break them lose.