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Rocker box stud

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Rocker box stud

Posted by George Phillips at January 28. 2017
Hi Guys, I've found why there is a constant oil mist round the top of the engine. One of the rocker box retaining studs has shed its threads in the alloy head (55 ES2). It's the centre front one at the rear of the exhaust valve. Has anyone any idea what size/thread it is as i intend to fit a helicoil - unless someone has a better idea? George

Re: Rocker box stud

Posted by Barry Carson at January 28. 2017

Re: Rocker box stud

Posted by George Phillips at January 28. 2017
Thanks Baz. I'm hoping not to have to send it off.But I'll wait for more views. G

Re: Rocker box stud

Posted by Barry Carson at January 28. 2017

Re: Rocker box stud

Posted by George Phillips at January 31. 2017
BTW Baz, I forgot to ask - do you know the TPI of the stud at the cylinder head end? George

Re: Rocker box stud

Posted by Barry Carson at January 31. 2017

Re: Rocker box stud

Posted by George Phillips at January 31. 2017
Hi Baz - after a bit of research I find that the stud should be a 5/16" with a TPI of 26. Now I've got to find if Time Sert or Helicoil do that size. Thanks for your help - George

Re: Rocker box stud

Posted by Ian MacDougall at January 31. 2017

George, do these studs not have different thread form at either end? 26tpi (Cycle) for the rocker box nut, 18tpi (BSW) where it screws into the alloy head. My '56 19S alloy head is definitely 18tpi (just checked the head lying on the bench).

Ian McD

Re: Rocker box stud

Posted by Ian MacDougall at January 31. 2017

George, do these studs not have different thread form at either end? 26tpi (Cycle) for the rocker box nut, 18tpi (BSW) where it screws into the alloy head. My '56 19S alloy head is definitely 18tpi (just checked the head lying on the bench).

Ian McD

Re: Rocker box stud

Posted by Barry Carson at January 31. 2017

Re: Rocker box stud

Posted by George Phillips at January 31. 2017
Now I'm getting confused Baz! Which chart are you referring to? I believe the threads are different at each end of the stud but I'm on about the end that screws into the alloy cylinder head. George

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Posted by George Phillips at January 31. 2017
Doh! Just realised you're talking about the chart you attached earlier on. My apols. But that's Whitworth and I think the cylinder head thread is 5/16"BSC at - I thought - 26TPI? george

Re: Rocker box stud

Posted by Barry Carson at January 31. 2017

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Posted by George Phillips at January 31. 2017
Oh well. Back to square one! I'll keep digging. I need to get it right so's I get the correct helicoil or insert. George

Re: Rocker box stud

Posted by Dan Field at January 31. 2017

I thought all 55's had wellworthy heads?

Re: Rocker box stud

Posted by George Phillips at January 31. 2017
Don't know what that is, Dan. Mine has an alloy head. Is that a "Wellworthy"? Does this affect the thread - or rater, the TPI. George

Re: Rocker box stud

Posted by George Phillips at February 01. 2017
Sorted! After an interesting and informative telephone chat with Ian I now know that the stud is a 5/16" with a Whitworth (coarse) thread into the head and a fine (26TPI) BSC thread for the nut. Now I can set about sourcing a Helicoil or insert set for the damaged thread in the head. Many thanks for all your help, Ian. George

Re: Rocker box stud

Posted by Barry Carson at February 01. 2017

Re: Rocker box stud

Posted by Dan Field at February 01. 2017
Previously George Phillips wrote:
Don't know what that is, Dan. Mine has an alloy head. Is that a "Wellworthy"? Does this affect the thread - or rater, the TPI. George
Hi George As far as I know the alloy head on an ES2 of that era was a Wellworthy head, although the head is aluminium the combustion chamber is iron, hence the name "iron skull". Mine says wellworthy on the side, but am not sure if they all did. Anyway glad you got it sorted, it was always going to be a whitworth thread in my mind, I guess you know the front and rear studs are a smaller diameter than the others. Dan

Re: Rocker box stud

Posted by George Phillips at February 01. 2017
Thanks Dan. Life is one great learning cycle! I'll check what's written on mine tomorrow. It certainly has an iron inner. I realise about the front and rear studs. the one last confusion is that then rocker box is held on with studs on my bike but RGM tell me it's a bolt. They don't do a stud. I'm trying to glean from them what the thread is so's I don't buy the wrong helicoil. And so it goes on........... George

Re: Rocker box stud

Posted by Ian MacDougall at February 01. 2017

The earlier iron head models have bolts holding the rocker cover, the alloy head models have studs. I guess the thinking was that bolts could be removed & replaced any number of times from an iron casting but with an alloy casting there would be a risk of damaging the threads so preferable to remove the nut from the stud. It also means that iron head rocker boxes can be removed with the head in situ so the RHS cylinder head sleeve nuts become more accessible. I have never removed a rocker box from an iron head - do the bolts have the same thread as the lower end of the alloy head studs? If not this may explain why George's research led to Cycle rather than BSW. Someone will know.

Ian McD

Re: Rocker box stud

Posted by George Phillips at February 02. 2017
Once again Ian, that makes a lot of sense. problem is that at present I'm getting two different answers and both seem feasible. I may have to go down the bolt route as it seems the only thing available. Once RGM confirm the thread type/ size I can move. Thanks again. George

Re: Rocker box stud

Posted by Barry Carson at February 02. 2017
Attachments

Re: Rocker box stud

Posted by Albert Sheean at February 02. 2017
Previously George Phillips wrote:
Hi Guys, I've found why there is a constant oil mist round the top of the engine. One of the rocker box retaining studs has shed its threads in the alloy head (55 ES2). It's the centre front one at the rear of the exhaust valve. Has anyone any idea what size/thread it is as i intend to fit a helicoil - unless someone has a better idea? George
Hi George, I had a similar issue with my 1958 Model 19S. The bolts were a 5/16" BSF (5/16"-22TPI) thread and I got a helicoil kit from Armstrong. Regards, Albert.

Re: Rocker box stud

Posted by Dan Field at February 02. 2017

If I get a chance today I'll take mine off and measure the thread. Tracy tools are good for helicoil sets.

 

A tip for removing the rhs head sleeve nuts- I loosen them with a ring spanner then use a strip of stout rubber to pull them undone, you can then release the tension, slide the strip back and start again.  The nuts have to be fairly easy to turn but I can get the head on and off in a jiffy now!

Re: Rocker box stud

Posted by George Phillips at February 02. 2017
So grateful for all your inputs guys. Information overload! I've taken the plunge and ordered a 5/16 BSF bolt plus a helicoil kit from RGM. Total cost about £40. Expensive for what is effectively a stud replacement but there you go. Onwards and upwards! George

Re: Rocker box stud

Posted by George Phillips at February 02. 2017
Just checked, Dan, and it is indeed a Wellworthy iron skull head. Also thanks for the tip. I've put a hold on my order as another query has arisen over the efficacy of changing what may well be a Whitworth thread in the head to a BSF. All good fun!! George

Re: Rocker box stud

Posted by Barry Carson at February 02. 2017

i will exit stage left

Re: Rocker box stud

Posted by George Phillips at February 02. 2017
Very drole, Baz. Your obviously a man of infinite wit! George

Re: Rocker box stud

Posted by George Phillips at February 02. 2017
Very drole, Baz. Your obviously a man of infinite wit! George
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