Stock Head Studs Constantly Loosening

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robertv

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Hello all. My first Norton. A '74 850. I have built many vw engines over the years. Like maybe 800 or more for customers. When I did the pistons rings and valves, I used the stock head studs. Here's the deal, After less than 20 miles running, all of my head studs have loosened.
I have retorqued several times already. In retrospect, I should have gone with stainless. Head gasket not leaking and no oil leaks, but when does it settle in? What are your thoughts of replacing them one at a time with stainless? Motor seems strong, maybe a bit ticky when hot off the highway. Appreciate any ideas you may have. Thanks, Robert
 
Are you talking about the 3 studs in the head only, or are five bolts and two nuts (studs in barrel) loosening too?
 
That could well be. The four head through cylinder bolts are doing the same. The engine was a mystery (crgslst) buy from a questionable individual who had little information. Not registered since 1994, but had a valid title. So no overheat issues known.
Holds nice oil pressure. Runs very strong. Should ride for 60 miles and see what happens I suppose.
 
Last retorque, the center front stud was down to 4 lbs.The rear nut was pretty good. the two front upper nuts were down to 10lbs. The two front lower up through cylinder bolts were quite loose also. Bolts (4) through head to cylinder always loosen. So everything really, loosens. No oil or compression leak between head and cylinder
I have not exceeded 55mph.
 
robertv said:
the two front upper nuts were down to 10lbs.
Click to expand...
There is something very odd happening if those 2 nuts are loosening. They are on studs threaded into the cast iron barrel (I presume yours is OEM?)

Based on what you've said so far, I would be pulling the top end off for closer inspection
 
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Was your motor ever very hot in the past ?, I know some car heads lose their heat treatment, the head bolts or nuts can sink into the alloy.
 
What headgasket, copper or composite (which need quite a few retorque sessions for first few hundred miles upto 1 k miles)?

Is your torque wrench calibrated recently? Any anti seize in use?
If continues to be a problem, replace all head fasteneds for good measure (ARP sets from CNW or try the waisted head bolts from JS Motosports).
 
As Tornado says, if you’ve got a new composite head gasket they crush a lot and need regular tightening until it stops crushing. Likely somewhere around 7-800 miles or so.
 
The composite gaskets from RGM are much worse for crushing than the Andover ones. Last time I had the head off I used an RGM composite gasket and after a decent run the fasteners were only finger tight. Retorqued them and after next ride they were loose again. I replaced the gasket with an Andover one which I did retorque a couple of times but had not loosened much, if anything at all. Lesson learned for me.

I did email RGM to tell them but as they don't appear to read emails I doubt they will do anything to improve the quality of their head gaskets.
 
New (better quality) studs/nuts are not necessary assuming the originals are not buggered. The loosening of the fittings is a function of proper (sufficient) tightening and the type of head gasket. The last head gasket I installed on my '73 some years ago never needed any retightening at all. Sadly, I can't remember what brand/type of gasket it was. :(
 
I know this might be unpopular, but hey ho…

I was told by an old Norton racer some years ago that his ‘trick’ was to overtighten by a few ft lbs on initial assembly.

I’ve tried this, and it does indeed greatly reduce the problem. Obviously, you shouldn’t go berserk with the wrench.

Makes me wonder if the factory did this? And / or if their gaskets were better / different, as they sold bikes that left the showroom and then weren’t re-torqued until the first service, which I assume would have been at 500 miles ?
 
MexicoMike said:
New (better quality) studs/nuts are not necessary assuming the originals are not buggered. The loosening of the fittings is a function of proper (sufficient) tightening and the type of head gasket. The last head gasket I installed on my '73 some years ago never needed any retightening at all. Sadly, I can't remember what brand/type of gasket it was. :(
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Loosening can also be reduced by using waisted bolts - particularly for the 3/8" ones. No point with the 3/8 studs as they're clamping cast iron - same expansion coefficient as the studs.
Their extra elastic springiness means less crushing damage to heads.
 
robs ss said:
Loosening can also be reduced by using waisted bolts - particularly for the 3/8" ones. No point with the 3/8 studs as they're clamping cast iron - same expansion coefficient as the studs.
Their extra elastic springiness means less crushing damage to heads.
Click to expand...
There’s no doubt that the waisted stem fasteners are better… that’s why almost all automotive OEMs use ‘em.

They provide better long term sealing and less damage to the head as you say.

But they don’t really prevent the issues caused by a squishy new head gasket bedding in.
 
Nortoniggy said:
The composite gaskets from RGM are much worse for crushing than the Andover ones. Last time I had the head off I used an RGM composite gasket and after a decent run the fasteners were only finger tight. Retorqued them and after next ride they were loose again. I replaced the gasket with an Andover one which I did retorque a couple of times but had not loosened much, if anything at all. Lesson learned for me.

I did email RGM to tell them but as they don't appear to read emails I doubt they will do anything to improve the quality of their head gaskets.
Click to expand...
I have used both the green composite gasket and Reinz gasket without an issue. I do prefer the Reinz gasket only because I found the Hillman Imp Reinz head gasket never failed on my tuned Imp. I think its compression ratio was 11:1 and fitted with a Piper cam.
 
Fast Eddie said:
There’s no doubt that the waisted stem fasteners are better… that’s why almost all automotive OEMs use ‘em.

They provide better long term sealing and less damage to the head as you say.

But they don’t really prevent the issues caused by a squishy new head gasket bedding in.
Click to expand...
Yet to be proven that that's the issue.
Apparently VW flat fours also use waisted head fixings
 
robertv said:
Hello all. My first Norton. A '74 850. I have built many vw engines over the years. Like maybe 800 or more for customers. When I did the pistons rings and valves, I used the stock head studs. Here's the deal, After less than 20 miles running, all of my head studs have loosened.
I have retorqued several times already. In retrospect, I should have gone with stainless. Head gasket not leaking and no oil leaks, but when does it settle in? What are your thoughts of replacing them one at a time with stainless? Motor seems strong, maybe a bit ticky when hot off the highway. Appreciate any ideas you may have. Thanks, Robert
Click to expand...
"Stock head studs": If you mean the three that screw into the head and are tightened from below and are the ones the factory put in, then you should not be having a stud pulling problem. If you mean you bought new of those studs from AN, they are likely pulling, see: https://gregmarsh.com/MC/Norton/Info/HeadStudStudy.aspx Also, according to SR N3/68 the torque should increase from 30 (3/8")/20 (5/16") to 35/25. I do not do that because the later MK3 workshop manual still says 30/20 and pulling the three studs from the head becomes even more likely.

The four outside bolts, the front center bolt, and the two 5/16" front studs all screw into the barrel so they are unlikely to pull and are unlikely to loosen. This, IMHO, only leaves the head gasket crushing for those.

If you are using any sort of lub on the threads you are over tightening if using a torque wrench.

I don't see the point in changing to stainless.

Re-torquing a couple of times is required with a composite head gasket - you have something abnormal. I only use the composite head gaskets from AN and I don't have anything close to what you are saying.

You could switch to copper, but note that they are not factory annealed and on a Commando some sealer is required.
 
Use solid copper gaskets with pliobond sealer and waisted triangular studs with thread inserts - end of problem.
Stock Head Studs Constantly Loosening
 

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