Nyloc Self-locking nuts

Old Fogey UKOld Fogey UK Posts: 732Expert Adviser
Can I use Nyloc self locking nuts on my conrod bolts ?
Can they be torqued to the same setting as ordinary nuts on conrods ?


  • bob wardbob ward Posts: 1,288Senior Contributor
    I know that some have but I wouldn't. The nylon insert isn't going to melt at the temperature inside the sump which is around 80°C but it will be softer and not gripping as hard as when it was installed.
  • GeoffGeoff Posts: 4,259Senior Contributor
    I would concur with Bob.   I wouldn't be wanting to take the risk myself.
  • Old Fogey UKOld Fogey UK Posts: 732Expert Adviser
    Bob and Geoff - thanks very much, your advice will be taken.
  • Old Fogey UKOld Fogey UK Posts: 732Expert Adviser
    Bob and Geoff - what sort of nuts would you use instead ?
  • JACK356JACK356 Posts: 200Member
    Why change the original rods? It's not a Formula 1 engine    :p
  • Courtesy ManCourtesy Man Posts: 198Expert Adviser
    I don't think the question is regarding the rods but rather how to lock the nuts - originally a thin washer type gizmo called a pal-nut was used but unlikely to be available new or desirable. A self-locking nut seems best.
  • GlowplugGlowplug Posts: 2,200Expert Adviser
    Old Fogey UK; I believe you are asking for the experience of those who see your post... how to secure the rod bolts in your engine once they are torqued.   The way I would recommend is ... search internet with this search “ lock nut for piston rod bolt” the pictures represent some I found.. the PAL NUT from Jeepster man is what many Hudson engines were equipped from the factory...
  • Old Fogey UKOld Fogey UK Posts: 732Expert Adviser
    JACK356 said:
    Why change the original rods? It's not a Formula 1 engine    :p
    I'm not changing the conrods. I'm having the cylinders re-finished.
  • Old Fogey UKOld Fogey UK Posts: 732Expert Adviser
    Thank you to all for the advice.
    I am having the cylinders re-honed on Monday.
    The re-honing guy thinks we can get away with reusing the existing lock nuts but I'm taking a rain check on that when the pistons and rods come out.
    If nuts have to be changed, that's when your advice will be helpful.
  • bob wardbob ward Posts: 1,288Senior Contributor
    I'd be thinking of good quality well made grade 8 nuts and loctite.
  • Old Fogey UKOld Fogey UK Posts: 732Expert Adviser
    bob ward said:
    I'd be thinking of good quality well made grade 8 nuts and loctite.
    Do I torque as stated in the Manual if I use Loctite ?
  • 54coupe54coupe Posts: 761Member
    I use Palnuts (sometimes called push nuts, or tinnerman nuts)on all of my builds McMaster Carr sells a 3/8-24 thread, package of 100 for $12.00 I would not use anything that wasn't designed specifically to be a con rod bolt/nut. They are a high strength fastener, and I don't think a nylock nut is up to the task.... My 2 cents.
  • DeletedDeleted Posts: 27Member
    edited May 14
    Most loctite fails with heat, that’s how your supposed to remove fasteners that are loc’d in.

    I wouldn’t put any nyloc inside an engine

    I have no experience with Conrods bolts but NORD-locks are a great product that I’ve used with great success. NASA did a few studies back in the day on locking washers and determined split washers did very little to prevent bolts coming loose, the washers with the twisted fingers around the edge (forgot the name) were determined to offer ZERO protection.

    iirc nasa prohibited the use of the 2 aforementioned washer In favor of the nordlocks but this was 10 years ago I think so who knows now.

    lookem up n check them out
  • GeoffGeoff Posts: 4,259Senior Contributor
    Stick with the original split pins David.  
  • blondwookieblondwookie Posts: 225Member
    Here is my two cents on nuts. If you can find Stover nuts use them. They make them in course and fine thread. Once they are torqued they stay put for good
  • cheyenne7271cheyenne7271 Posts: 310Member
    I used to sell premium fastening systems through Lawson products. They sold regular high quality gr 8 and upgraded severe usage gr 8 bolts. In every application it was proven that a split lock washer ( even a high strength washer) would fail every time before the fastener that had hardened flat washers on either side. Doesn’t totally apply here, on a conn rod, but for a critical application never use a split washer. 
  • Old Fogey UKOld Fogey UK Posts: 732Expert Adviser
    The con rods and pistons have been taken out and the bores re-honed and the good news is the bores, pistons and rings are OK.
    However, the engineer who did the honing felt that the con rod bolts and nuts had been excessively tightened by the engine rebuilder and felt I should replace them.
    The ROC don't list these items - are they something standard size that can simply be bought at any auto store ?
    Please could someone tell me what size I need to go for ?
    Presumably, they're available in sets ?
  • GeoffGeoff Posts: 4,259Senior Contributor
    They are 3/8" U.N.F. and are high tensile.   They are of course not standard bolts, so if you buy new bolts they will have to be grade 8 minimum and you will  have to grind one side off the head so they fit in  the connecting rod.  Plus if you are using split pins you will need to drill holes in  the bottom of them.   There is a brand of bolt here which are labelled "Unbrako", and these are extremely tough, don't know whether they are available in the U.K. , but  it appears from watching shows like "Flipping Bangers" and  "Wheeler Dealers" that you can get anything for anything over there.  The bolts used from 1938 onwards had a slightly thicker shank, and the holes in the rod were slightly smaller, so they were a precision fit, unlike the earlier ones where they were a bit less precise.  
  • Old Fogey UKOld Fogey UK Posts: 732Expert Adviser
    I've found out that the ROC now stock the correct bolts and nuts.
    They are expensive - as you know, Geoff, from my private email - but as I want to finish the job quickly, I'm going to get them.
    If anyone  believes what they  see and hear on Flipping Bangers and Wheeler Dealers, they must be fond of fairy tales ! 😄😄😄
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