Going to try a more responsible post about rod nuts

I recently tried to marry my engine thread under XKE to the XK forum and made a mess of it. So, here’s an original thread. The engine is a 3.8 from Oct 1962, original in my car. There are 3 things I need opinion on: the main bolt washers, the rod nuts, and the staking of the rod journal plugs.

Pics below. These all from a build done around 1995.
Main bolts are supposed to have a tabbed washer securing the bolt head. Mine have a washer that is not a split washer by has some radial marks around it. Can anyone recognize it?
The rod nuts are 12-point nuts, no washer under them. I know some XK engines used a similar 12-point nut, but it looks different that mine. Comments please…am I safe?, the rod journal plugs have clearly (at least I think so)) been removed. Do you agree? What about the “minimal” staking that I now see? Good enough? Should I remove one to see if sludge exists underneath?

Uploading: No 3 Rod nuts A.JPG… Uploading: No 5 Rod Journal Plug C.JPG…

The 12-point nuts are likely Chevy nuts, and are a good upgrade.

The mains should only have hardened, flat washers under them.

Yes! Find the least staked one, and confirm if it’s been cleaned. Grind off the stake divots, and use a 3/8" drive hex bit.

At a guess, I think they’ve been done, but, make sure.

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Scot, in the late 60;s they switched to plain washers under the main bearing bolts and on the rod bolts they used 12 point nuts with a inclusive “washer” surface. The nuts you have are after market, but because Jaguar use a much lower torque loading than most others, I would’t anticipate any problem.

This is a V12? This is the V12 forum so I figured I’d double check…

No it’s an XK. I can screw up in so many ways… Sorry for posting in the wrong forum

Thanks to All, I think the answers satisfy. I will look up the torque values, but should I use that on the mains and rods or something different with these fasteners?

I‘ll move your thread for you.

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Nope: book values should be fine with those fasteners.

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Torque values are always a function of the male thread form. Absent two dissimilar materials, the female form will always be slightly stronger. Steel on steel, the male side rules.


Carroll would be proud of ya, son!


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I really don’t like the looks of those 12-point conrod nuts. Really sorry design. If I were rebuilding this engine, I’d replace those with some nuts with a proper washer face, sorta like these:


Hafta make sure, though, that the washer face isn’t too broad so it doesn’t sit properly on the surface of the end cap.

I think that dates way back to Machine Design 1!

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Well spotted Kirbert. those are not the jaguar 12 point nuts that im familiar with. the ones on your link look to be the ones I bought from SNG recently.

12 point nuts and cap screws are not cheap. They are generally high-specification items. You are not going to find them at the corner hardware store. They generally carry a manufacturer’s mark, making them identifiable.

Conrod nuts are not the place to cheap out, though.

Sorry folks…out of town on grand baby duty 'til after T-giving…

Thx David for moving my errant thread.
Mike S, for me it was engr mech. 101, but I believe Wiggles is talking about the Garder of Eden. You wonder why he’s called Wiggles, hmmm.
Kirby, I think they’ve been identified as possibly Chevy 12pt. Right or wrong, an engine builder thought they’re good in the mid-1990s. I like ARP bolts myself and am willing to change…for the better. The nuts your thread points to leads to an assortment of similar 12 poiinters. How do I know which are the right ones? I guess I could go to SNG, but I can buy cheaper at Summit for the same if I identify them correctly.
I’d agree that cheap is not this game, but less expensive for the same will do. :slight_smile:
Expect delays in my answer, please.

Let’s not put the cart before the horse. Unless you know for dead certain what the rod bolts are, the nuts are of minor importance. I have never, ever, seen a broken or stripped nut be the cause of any automotive or industrial mechanical failure. Within similar metallurgy, it’s always the bolt that fails. Always.

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Mike why do state the motor had marine service? It is original to my 887030. I do agree marine applications are generally more severe than automotive.

And actually, i’ve bent rods and holed pistons before, but I have never lost a nut … at least that I recognized. I had a wayward youth.


Oooops! My mistake! I mixed up two threads! Ignore the marine part. The rest is still true. The bolt will always fail before the nut. (I’ll go back and delete the marine reference. Mea culpa!)

No es importante.

But I would like to improve my odds for success by using good “stuff”. that said, I don’t see this engine as being a highly stressed motor. Does anyone?