Connecting Rod Nuts

I have been into a few newer engines. The rod nuts were simply just tightened to the desired torque. Same with the main bearing bolts just tightened. On my old A/C from the late 30's. It has cotter keys after torqueing, Installed in the rod castle nuts. May I say, a real pain to remove, and reinstall, especially when I have a limited time I can lay on my back at one time. What if I install a grade 8 nylon lock nut? I can't see how the nut can back off. If they had these nylon lock nuts back then do you think they would have used them. What do you think? I may have discussed this a year or so ago, but don't remember the outcome. Stan

I'm not sure what the engineers were thinking back then. That is something long abandoned.

I just don't see a properly torqued nut coming loose.

I would not loose any sleep just leaving the cotter pins out. To me, proper torque is more important than trying to line up cotter pin holes!

All you need is a small drop of Loctite.

I had a 1976 International 1600 Loadstar dump, one day it started knocking and quickly came to a catastrophic end. When I pulled the pan one connecting rod bolt lay in the pan the other had broken off. It was never made for wire and I guess they thought it wouldn't come out.

A properly torqued nut will not come loose. However, most farmers from 70 years ago didn't have a torque wrench.

I once had a competition tractor engine rebuilt at a high dollar shop. At the rime I had recently been into one with pal nuts on the rod nuts. I asked the shop owner about them and his response was that he would rather rely on the proper stretch of the bolt to keep the nut tight.

Had 2-3 cotter pins break (vibration) and the pieces were picked up by the oil pump. Replacement bolts did not have castellated nuts; 12 pt. Jaguar 4.2 L.

(quoted from post at 05:12:23 03/16/17) I have been into a few newer engines. The rod nuts were simply just tightened to the desired torque. Same with the main bearing bolts just tightened. On my old A/C from the late 30's. It has cotter keys after torqueing, Installed in the rod castle nuts. May I say, a real pain to remove, and reinstall, especially when I have a limited time I can lay on my back at one time. What if I install a grade 8 nylon lock nut? I can't see how the nut can back off. If they had these nylon lock nuts back then do you think they would have used them. What do you think? I may have discussed this a year or so ago, but don't remember the outcome. Stan

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I wouldn't put A nylon locknut on there and I don't think they would have used em back then even if they had em that nylons gonna degrade and in the end you'll have the equivalent a square stove nut

. Here are a few no-no's working with fiber-locking nuts:

Bolts with damaged threads, rough ends or a 5/16 inch or larger bolt with a hole in the shank and having burrs at the hole are unacceptable for use with fiber-locking nuts.

Do not tap (run a tap through) the fiber insert.

Fiber insert self-locking nuts are limited in application to a temperature of 250 degrees F. The reason for this limit is because the effectiveness of the self-locking properties will reduce beyond this point.

When proper preload of a bolt is applied and maintained, regardless of the equipment used to load the bolts in a joint, the bolt cannot fail from fatigue, because it will experience no change in stress Anyone can cause any fastener to fail by simply over tightening or under tightening it. To review, torque is used to turn a nut to stretch a bolt and provide clamping force. It is usually done with a manual, hydraulic or pneumatic torque wrench based on Thread pitch( Typically fine thread vs coarse thread. The pitch of a Bolt thread is a measurement of how closely the threads are spaced. It can be expressed as the number of threads per Inch and can be measured with a thread gauge) The Diameter of the bolt is also a factor as is the material strength and the engineered tension requirements for the load. Basically your best bet is to follow the engineering requirements on the tractor your working on they have a proven record. For instance if you apply torque with the nut at the cotter key hole or above it chances are good you will break the bolt or stud. There are other locking methods that have been used and would assure you the nut will not back off Case has used a washer-lip under the head of the bolt bend one flange up on the bolt the other down on the rod cap. That may work with a nut as well Ill add a picture.
Best of luck with it Byron

Nylock breaks down over time. Seen it too many times in industry. Loctite blue (242) is your friend. I have been using it on rod bolts for decades and none have failed. I don't trust bolt stretch and torque as I have seen it fail quite a few times over the years. When you think about how often those bolts expand and contract with the temperature, the work hardening it causes and the vibration it endures it's a wonder they hold up at all.

Chief, you may need to do a little digging, but in order to be certain of the amount of bolt stretch you really need to observe not only the prescribed torque value but also whether it is supposed to be wet or dry. With proper stretch of the bolt, any other means of making a nut stick to the bolt in a corrosion free environment are incidental.

Aviation industry sure likes their wire tied fasteners .

My 2 cents, Don't recall a nylock nut being tempered.Also are the nylock resistance to petroleum products without degrading.

One thing I did learn in the Navy was how to properly safety a nut. Stan

(quoted from post at 22:03:57 03/16/17) One thing I did learn in the Navy was how to properly safety a nut. Stan

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Did you just get out? I had the impression that you were older.