Using lock nuts on connecting rods

Red460 · Mar 2, 2009

I am volunteering at a railroad historical soc. to overhaul a 200 hp gas engine (1941 vintage) in an industrial switcher. Access to the connecting rods is through hand holes down between the frame. I cant see the rod caps I have to do everything by feel.
Q: Can I use nylon lock nuts on the rods to connect the rod caps.
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Janicholson · Mar 2, 2009

If safety wired nuts were used I would use safety wire to assure there retention. If bent tabs were used, I would make new ones. If the nuts that came off were not retained, I would see no reason not to use the nylock (assumes the threaded portion of the nylock nut is equal in threaded distance (engagement) as the original.)
Nylon can stand up to 400 degrees, and if it is that hot in the engine, it has other issues.
Working in the cramped space might requiremirrors, better light, and a helper. but risk is somthing I would not take in an engine that cannot be replaced. JimN

rustyfarmall · Mar 2, 2009

Using any kind of locknut will give false readings with your torque wrench. I would not use them.

J.J. from Afton · Mar 2, 2009

What Rustyfarmall said, locknuts, specially nylon equal false reading when you torque them. I reccomend using wire or make locking tabs to hold the nuts in place.

mattofvinings · Mar 2, 2009

Adding to above: I would not trust the nylon locking insert to hold up thru the heat inside an IC engine....

CGtractor · Mar 2, 2009

We use nylocks on almost everything at my work (food manufacturing) and while they may take the temperature of an engine, I have found that with time the oil and temperature will degrade the nylon locking material. I would never rely on nylocks in your application. As a side note the locking ability of nylocks is severely degraded after they have been removed once. Whatever the original locking method was is probably what you should stay with. If you feel that you need to augment that with something, use locktite.

Fixer · Mar 2, 2009

Only thing I would be conserned about is whether you could find a good grade of locknut. I think grade 5 is the best I've seen Bernie Steffen

teddy52food · Mar 2, 2009

If you have to go by feel, get a good light and a mirror and see how they are locked. How will you get a wrench on them if they are wired?

Red460 · Mar 3, 2009

Thanks for the responses. The people on this forum know engines. The original castle nuts had cotter pins in them. I dont want to take a risk with this engine. I will use the cotter pins.
Engine rebuild

Janicholson · Mar 3, 2009

Good reasoning. Best of luck on the project, it looks marvelous. JimN

Using lock nuts on connecting rods

Red460

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Janicholson

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rustyfarmall

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J.J. from Afton

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mattofvinings

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CGtractor

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Fixer

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teddy52food

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Red460

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Janicholson

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