Original vs Reproduction Con Rod Nuts and Loctite

elefantrider

elefantrider

Joined
Apr 6, 2013
Messages
1,439
Country flag
Did some quick testing and observed that sometimes the original rod nuts will lose a lot of their mechanical "lock" after being used with red loctite, or heated to separate.

Has anyone tested rockwell hardness or the locking function of replacenemt nuts vs originals?

If the repro nuts quality meets or exceeds the originals, I am thinking it is wise to replace the original nuts, especially after they have been used with red Loctite.
 
Agreed.

BUT, all this assumes the replacements are made to proper standards. Most parts supplied now leave me wondering what lowest bidder hut they were made in, the earmarks of quality noticeably absent.

JMWO
 
I only use Andover Norton sourced nuts and replace every time.

There was a piece done a while ago regarding the bolts, and Wassells had their pattern bolts tested and were shown to exceed OEM specs. For the price I replace these too
 
I always replace nuts and bolts
But I have heard the argument for re using con rod bolts etc because they have been tested?
 
That's because the Wassel bolt was not made to OEM tolerances - and yes, I have the proof and the UKAS lab tested results, infact I used the same lab that tested them for Wassel. If made to the correct dimension it would not be any stronger.
 
If reproduction nuts measure the same hardness and are locking the same as originals, I think it would be good to replace.
Would be good to see a hardness and breakaway torque comparison of both.

Factory automaker con rod nuts and even most aftermarket replacements (ARP), don't have the lock. Nor do they use Loctite.
But they have a lot less vibration.

To loosen and remove Red 263 Loctite, the threads need about 400 degrees. The temp from the flame will color the nut.

With the locking function of the original nut, Loctite is probably not needed......just added for extra insurance.
 
I recently built an A65, & as I could not be certain where, or by whom the available BE bolts/nuts were manufactured, I sent to the states for a set from ARP, which I felt were worth the cost for my peace of mind. On Nortons I would trust AN. As for thread locking,over forty odd years I have built a lot of engines for bikes & cars, & have never used Loctite on a big end bolt. I have not had a single one come undone.

Martyn.
 
I don't think they unwind. I think the threads get beat out and or the bolt itself stretches.
 
I know how you feel with so much crap made in China etc , if you can't verify the source then , testing the nut will help ease your mind, of it not holding at 7250 rpm .
 
I would worry less about the material properties of the nuts, than about the tolerance on the threads. As you wind the nuts onto the bolt by hand, the action should be smooth and fairly tight. There should be no slop.
 
Madnorton said:
That's because the Wassel bolt was not made to OEM tolerances - and yes, I have the proof and the UKAS lab tested results, infact I used the same lab that tested them for Wassel. If made to the correct dimension it would not be any stronger.
Click to expand...
I'm happy to accept what you say, but that's not the point. Are they at least as good as OEM? Are they at least as good as what AN supplies? What dimension is incorrect?

I'm a big fan of AN, but that's not to say that AN is always best. PM me if you want to know more.
 
Can you e-,Mail ARP and ask them for big end specific nuts ? , id feel good with their brand nuts holding it together down there .
 
acotrel said:
I would worry less about the material properties of the nuts, than about the tolerance on the threads. As you wind the nuts onto the bolt by hand, the action should be smooth and fairly tight. There should be no slop.
Click to expand...
For aerospace grade locknuts, there's a run-down torque and a locking torque specified. For the application I was involved with the assumption was after 5 cycles the nuts were scrap, but having a numerical pass-fail value was most important - and easier to verify...
 
marshg246 said:
I'm happy to accept what you say, but that's not the point. Are they at least as good as OEM? Are they at least as good as what AN supplies? What dimension is incorrect?

I'm a big fan of AN, but that's not to say that AN is always best. PM me if you want to know more.
Click to expand...
Greg, The waisted portion of the bolt on the samples we tested were oversize which of course makes them stronger. Like a lot of things in the Norton the bolts are overkill for what they are needed to do, if fitted correctly they don't fail no matter where they come from, as concours says above they are often blamed for a myriad of failures that cause the rods to fail from incorrectly fitted piston rings, to big end oil failure. A test to say that one bolt is stronger than another when they are all suitably strong enough is just a trick to to convince the unknowing to buy their product.
 
Another possible reason for failure is the eccentric head of the bolt not bottoming out in the rod. I am just putting the finishing touches to a MK2a I've built for a friend, & as part of the engine work I had to recut the rod counterbores, because the bolt heads had dragged material from the edge of the counterbores preventing them from bottoming out. As far as I know it left the factory like that, as I don't think the bottom end had ever been apart previously. Having said all that it didn't fail, so what do I know?
 
Madnorton said:
Greg, The waisted portion of the bolt on the samples we tested were oversize which of course makes them stronger. Like a lot of things in the Norton the bolts are overkill for what they are needed to do, if fitted correctly they don't fail no matter where they come from, as concours says above they are often blamed for a myriad of failures that cause the rods to fail from incorrectly fitted piston rings, to big end oil failure. A test to say that one bolt is stronger than another when they are all suitably strong enough is just a trick to to convince the unknowing to buy their product.
Click to expand...
Thanks, and agreed on all.

I've read Wassell's lab report and I took it to mean "just as good as" even though it really says "better than". Since Wassell's products are often considered substandard they have to defend themselves in many cases to sell. The truth is that some of their products are superior to other after-market, some are crap, and some are "just as good as". Anyone who bought Lucas-type products a few years ago and buys genuine Lucas today can see the difference.
 
Personally, I have no reason to doubt the workshop manual. Reuse bolts, always new nuts, and no need for thread locker. This is one place where I always use a torque wrench and clean dry threads and work up to full torque alternating between the nuts on a conrod.
 
You must log in or register to reply here.

Similar threads

H
  • Locked
Quick question...Con Rod nuts
Replies
3
Views
534
L.A.B.
L.A.B.
Back
Top