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FT: Frame (Twin) cylinder head brackets

Bill Thomas

Well Known and Active Website User
VOC Member
If we are talking about 35lb foot lb for the Big cylinder head nuts,
I would say the same for the Big Nuts above them, But there is no set torque settings in the books,
Cheers Bill.
 

vin998

Well Known and Active Website User
VOC Member
VOC Forum Moderator
What type of cylinder studs does your bike have? The early series B two piece type with the hollow outer threaded tube for the cylinder head and the 3/8" inner stud for the head bracket should be a lower torque than the later solid studs. Most bikes mid 1948 onwards have the solid cylinder studs.

Simon
 

vibrac

Well Known and Active Website User
VOC Member
At the risk as repeating an old song, there are no official torque figures for the Vincent there were no torque spanners on the assembly lines in 1948. The only time I use a figure is as Bill says is the cylinder head nuts (And even then I say 32 lb ft not Bills 35 !:)) Otherwise like the factory you need to be a fitter not an assembler.. tight is tight too tight is busted!
 

Albervin

Well Known and Active Website User
VOC Member
I am continually amazed that people who have never rebuilt or restored a bike think they can learn the process by working on one of the most expensive production motorcycles ever made. A set of standard BSF and BSW spanners plus a 1/4" drive socket set is a good starting point. You may need a 1/2" drive for the ESA nut on the twin. I have a rule that the small stuff (2BA, 1/4" BSF etc) barely need more than two fingers to tighten. The crankcase studs are routinely over-tightened by people who think the cases will blow apart unless the nuts are pulled down with the force of Atlas! There are tables available that give torque figures according to thread dimensions but be aware that our bikes are mainly alloy and not cast iron or heavy gauge steel (as in Harleys).
 

Bill Thomas

Well Known and Active Website User
VOC Member
I think we all have to learn by our mistakes, I have made a few !,
Or we would do nothing,
The information on the computers now is Huge, Making almost anything possible ,
Just some of it is wrong !!, Been watching cutting down trees etc,
" Or how to get Killed " doing it !!,
So we have to chose who to trust, Maybe if 2 or 3 tell us the same , Should be OK ??.
 

greg brillus

Well Known and Active Website User
VOC Member
Well just to answer the question........The nuts are actually a thin nut, so the torque figure technically should be lower than a standard sized nut.........I would say 25 Ft lb's at most.........The lack of torque figures quoted from the factory was probably because the amount of leverage was dictated by the length of commonly used spanners from that era and a reasonable amount of pull exerted on this spanner with normal human strength.......... I suspect most of you are laughing at this comment........i think you will find it to be correct of normal engineering practice..........The main issue now, is so few people have this so called "Feel" from a lack of experience.........No need to feel bad about it......It is just how things have become........torque wrenches are cheap enough to buy these days, so if in doubt, use one.
 

MartynG

Well Known and Active Website User
VOC Member
I think we all have to learn by our mistakes, I have made a few !,
Or we would do nothing,
The information on the computers now is Huge, Making almost anything possible ,
Just some of it is wrong !!, Been watching cutting down trees etc,
" Or how to get Killed " doing it !!,
So we have to chose who to trust, Maybe if 2 or 3 tell us the same , Should be OK ??.
check my signature... loosely translates to "experience is an accumulation of mistakes"
 

Glenliman

Well Known and Active Website User
VOC Member
From Know Thy Beast-
"All head nuts require careful tightening , especially with the early hollow bolts (cf, chapter 7) which, according to the Instruction Sheets, require 30 lb. ft. and a torque wrench. Even with the later solid bolts, overtightening must be avoided, because owing to the difference in expansion rate of the steel bolt and the aluminium jackets, it can lead to distorted and damaged crankcase bosses. If a torque wrench is available tighten to about 40 lb.ft., otherwise use a short spanner and not too heavy a hand"

Given the difference in strength and feel in humans, the last bit about " not too heavy a hand" doesn't mean much to me, especially in a world where torque wrenches are readily available. Many if not most people working on Vincents are enthusiasts, not professional mechanics. Even there, torque wrenches are required on critical parts such as head bolts, wheel studs and a great many other things, if following textbook procedure.
If everyone had identical strength and sensitivity, hand feel might get you in the ballpark, but that isn't the case.
If not tightened adequately, the head joint will leak. If overtightened, then damage occurs, and it's not an easy fix.


So if in doubt, it would be safe and precise to use a torque wrench to the figures above.

Glen
 
Last edited:

vibrac

Well Known and Active Website User
VOC Member
The search engine at the top is your friend have a search. I am certain years ago the consensus was 32lbs ft. Thats what I use and have for years, light oil on the nuts run them down and back before fitting head. tighten to 30 leave overnight final tighten next day
 

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