Cylinder head bolt threads

[WEM]

1974 Commando MK II. Head is RH10. I’m getting ready to remove the three 3/8” studs from the bottom of the head prior to shipping the head for repairs to the exhaust port threads. The three studs correspond to head bolts 2, 7 and 8 I think. I’m wondering what threads these studs have so I can use correctly threaded nuts when double nutting them for removal. Thanks.

 

[L.A.B.]

You mean the outer ends of the studs which were thought to be (60 degree) 3/8" x 26 Cycle thread although they may in fact be (55 degree) Whit form as the rear nut is Whit form according to AN therefore the studs should be too.

Andover Norton - CYLINDER BASE/ HEAD NUT 3/8

CYLINDER BASE/ HEAD NUT 3/8

andover-norton.co.uk

 

[dobba99]

You mean the outer ends of the studs which were thought to be (60 degree) 3/8" x 26 Cycle thread although they may in fact be (55 degree) Whit form as the rear nut is Whit form according to AN therefore the studs should be too.

Andover Norton - CYLINDER BASE/ HEAD NUT 3/8

CYLINDER BASE/ HEAD NUT 3/8

andover-norton.co.uk

That would make the thread size to be 3/8 BSB (British Standard Brass) which is 26 T.P.I. by 55 degree thread angle

 

[L.A.B.]

Yes it should be the same as 3/8" BSB.

 

[WEM]

Thanks for the quick replies. Much appreciated.

I didn’t think to check the AN website.

 

[Tornado]

But you should have the nuts that came off those studs no? Just use them for the double nut removals.

 

[WEM]

I had the same thought but the three studs in question correspond to Bolts 2, 7 and 8 on the head bolt tightening diagram. Studs 7 and 8 are the ones that the unusual long sleeve nuts go on so those nuts are no good for double nut method and Stud 2 is the one in the centre of the back of the head under the fins. The nut for that bolt is too long to allow double nut method. I’m thinking about cutting a spare nut I have for Stud 2 in half, creating two separate nuts and using those to double nut.

 

[WEM]

Following up on my previous posts, the head is back from being repaired. Exhaust threads have been repaired. Head has been vapour blasted and looks new. New valves and springs have been installed. I’m about to reinstall the three studs that go in the bottom of the head that correspond to head bolts 2, 7 and 8. I know the nuts on these bolts have a torque setting of 30 ft/lbs. My question is should I torque the studs themselves to this setting when I install them using the double nut method? My plan is to use Loctite 243 on the threads that screw into the head.

 

[seattle##gs]

I asked this same question about a month or two ago. Did not come to much of a conclusion. Maybe 15 - 20 ft/lbs

 

[WEM]

I tried to search for posts on this topic before I posted and came up empty. Undoubtedly an indication of my ability to conduct a search. Would you mind directing me to the post you made. Thanks.

 

[WEM]

I asked this same question about a month or two ago. Did not come to much of a conclusion. Maybe 15 - 20 ft/lbs

I noted that the rocker spindle cover bolts that go into the head have a recommended torque setting of 8 ft/lbs and the three head steady bolts that also screw into the head have a recommended torque setting of 12 ft/lbs. What setting did you use?

 

[WEM]

I just found a post where Greg Marsh noted that he uses blue threadlocker, double-nuts the studs and snugs the studs with no torquing. Sounds like a reasonable approach.

 

[DennisMo]

I will soon reassemble my 850 head.

I just looked at Loctite for the head studs and think the temperature range of
the Loctite should be such that the temperature of the head does not soften or melt it.
In addition, I like blue Loctite as it should be easier to torque undo than red loctite

Blue 243 loctite goes up to 360 degrees F while blue loctite 246 goes up to 450 degrees F

So I am thinking of the loctite 246 and would appreciate any thoughts you have

Dennis

 

[Tornado]

When i did my head some urs ago guidance on here was ro use nothing on tge tgree studs andcto just nip them up without much torque. The studs have a non threaded section that will stop further turning it past head surface...applying excess torque only risks damage at that point.