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MG MGB Technical - Rocker Arm Stud Nuts

Am in the process of re-assembling a rebuilt engine. One of the new items being installed was new rocker arm studs and nuts. The nuts, Moss part number 310-140, are zinc plated, no grade marked. When torquing the first one to the required 25 lbft, the nut stripped out on the shaft. Tried to jamb a second (Moss) nut on top of it to remove the stud. Second nut also stripped out and neither could be removed. Purchased a nut splitter, removed the nuts and found the stud threads had been damaged when the nut stripped out. Replaced the stud with a used one and used four old OEM nuts to install the rocker arm.

Do not use the Moss rocker arm stud nuts until they have a chance to get rid of the bad ones they are currently selling. Les
Les Bengtson

Les,

Sounds like a mix-up in the parts room that they are not aware of, or it could be a procurement problem. Surely they know better, did you send a note to Craig Cody?

Regards,

L.C. '74 B/GT
Larry C.

Les-
Arrgh! Hopefully the old studs aren't metal fatigued and stretched. Moss should reimburse you for everything, including the studs.
Steve S.

I had similar problems with 1500 midget studs from
another mail-order supplier, and indeed with
B and midget
mail-order fasteners in general.

www.aptfast.com sells the ARP version of the B rocker studs by themselves if you e-mail them.
Ronald

Yes, I have left a message on Craig's voice mail. He is currently on vacation. Went out today and picked up some grade 8 nuts at the local hardware store and will use them in the future. The damaged parts are only worth a few dollars. Not worth worrying about. But, I would prefer not to have anyone else get the bad stuff and have similar problems. I am sure Craig will get it sorted when he gets back. Les
Les Bengtson

I had the exact same thing happen with these from Moss Europe, not sure if the source is the same though.
Matt
Matthew Crabb

I also had the same thing happen about two years ago. I think the parts came from Moss of Europe or they may have come from Victoria British. Good used nuts worked fine. Clifton
Clifton Gordon

Unreal. I've been chasing a problem with wandering valve clearances months, and just this afternoon tracked it down to stripped threads on a pedestal stud. Then I come in and read this. I don't know if the nut came from Moss, but it wasn't OEM and it wrecked the stud. The stud itself had a dimple in the top which I think means it should withstand a lot of torque?
Steve Postins

Steve-
The dimple means that it's an Original Equipment stud.
Steve S.

This doesn't surprise me. I haven't had this problem on rockers as all my parts are OEM however I have come across a much worse one which is safety critical and this involves the front suspension top and bottom trunnion nuts and bolts.

These can be of poor quality with rattling fit nuts which are not capable of being torqued satisfactorily. The material appears also to be low carbon steel which would strip even if the thread cutting was accurate.

Please all be very careful on this one which is highly safety critical.

I'm not going to divulge my supplier here save to say that it is a major UK mg specialist and not Moss on this occasion.
Iain MacKintosh

Dodgy parts quality? I can add to the hall of fame a rear suspension shackle that had the structural strength of fresh pastry. Again from "a major UK MG specialist and not Moss" that argued I must have used too much muscle. I was more concerned about warning them of the danger than the cost, as I know I had only about 15lbft of torque on the nut when the part crumbled. I haven't been back.....
Steve Postins

Steve and Iain. Unless you do like Chris Betson does (he has cylinder head studs custom made and hand inspects the parts he sells), you are going be be stuck with what the suppler to the retailer is selling. A lot of it is going to be to whatever specification is noted on the purchase order. Often times, the person writing up the purchase order is not a mechanic or a machinist and is working with information supplied by someone above them who may also not be qualified to determine exact standards. I suspect in my case, the purchase agent was told to order 5/16" UNF nuts and that is what was ordered. The nuts I received are similar to what is available in most hardware stores for light duty applications, unhardened and zinc plated. They should have been specified as a 5/16" UNF nut of grade 5 or grade 8, unplated. With minor parts like nuts and bolts, there are any number of suppliers. With some of the MGB only parts, there may well be only a single supplier. Thus, my making these problems known to the retailer, we have a fighting chance of getting the specification described more accurately and, perhaps, in solving the problem throughout the parts system.

One thing is very sure. The problem with bad parts is not limited to any specific retailer, nor is it limited to just MGs. Les
Les Bengtson

I had same problem. I think Moss needs to 'up the grade' of the nuts and studs. Luckily I still had the old factory ones which took the 25 lbs. torque.
Sam

Anyone know if the MGOC studs and nuts are of the correct spec?

Matt
Matthew Crabb

The rocker posts are held by two studs - the cylinder head studs and nuts which are 3/8 dia and the studs, if dimpled or have "22" on the end can be tightened to 55 ft lbs - unmarked studs to 50 ft lbs only. The second stud / nut is 5/16 dia and should be tightened to 25 ft lbs max.

I have never had problems with the zinc plated nuts supplied by my supplier - I use plain nuts on the end posts ( for clearance of the rocker cover nuts) and nyloc ones on the centre posts.
Chris at Octarine Services

So Chris, who is you supplier if I may ask?

Matt
Matthew Crabb

Got a telephone call from a Moss tech rep today. Craig Cody had e-mailed him and asked him to check out the problem. We discussed the torque spec used, 25 lbft, and the physical appearance of the nuts and studs I had received. (Nuts were zinc plated and studs were oil blackened as if they had been heat treated.) The tech rep also offered a refund on the parts. I greatly appreciate Craig following up on this and the fact that his representative took the time to call and discuss the matter so that their tests would duplicate my field experience. Les
Les Bengtson

Matt,

They come from a wholesale nut, stud & bolt supplier in Birmingham.

My point was that just because a nut etc is zinc plated it doesn't mean that it is not suitable.

I have had problems with some studs and nuts in the past - notably the head studs & nuts - I pay 50% more than the minimum possible for these items, simply to get the quality of thread form and strength.
Chris at Octarine Services

This thread was discussed between 02/01/2004 and 08/01/2004

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