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#261575 - 06/28/09 10:53 am Torquing cylinder head bolts  
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RetroRod Offline
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Hi fellow trouble shooters, makers, and fixerupers!!

My manual tells me to torque the 3/8" bolts to 18ft/lbs and the 5/16" bolt to 15ft/lbs.

Whilst there must be some sound engineering principle determining these torque settings, they nonetheless seem light on to me. At these pressures they are hardly tightened at all.

Are any of you applying more pressure than this, despite the Triumph instructions?

Pleased to hear from you as usual. RR


'72 Bonneville
"He who praises you for what you lack wishes to take from you what you have." - Don Juan Manuel
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#261580 - 06/28/09 12:02 pm Re: Torquing cylinder head bolts [Re: RetroRod]  
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Blapper Offline
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No need Retro. If your head is flat and your gasket well annealed, it is enough. If either of those conditions are not met, then over-tightening probably will not help.

Of course if you want to make the ali flow away from the bolts with heat, then go ahead and over-tighten them! wink

Just my 2c mate.

Blapper redwine

#261695 - 06/28/09 10:44 pm Re: Torquing cylinder head bolts [Re: Blapper]  
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RetroRod Offline
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Thanks for replying Blap, I'll stick with the recommendations I suppose, but I just wonder sometimes with many complaining here and there about the heads loosening. Cheers, RR


'72 Bonneville
"He who praises you for what you lack wishes to take from you what you have." - Don Juan Manuel
#261752 - 06/29/09 9:06 am Re: Torquing cylinder head bolts [Re: RetroRod]  
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The thing to remember is that the torque setup after rebuild is only temporary and will loosen as everything settles down sooner than you think! I know its a PIA to take the tank off every time but I would recommend that the first check is only 50 or less miles after first rebuild and then 150 miles followed by 500 miles. adjustment of the valve clearances is vital every time. These are only my recommendations based on my experiences (copper rockerbox gaskets improve settling time). Don't forget to check the cylinder base nuts at the same time. The other thing to remember is the torque settings are based on dry settings.
I seem to remember someone saying that the factory never used a torque wrench when tightening heads and just used to feel by experience but that might just be rumour.


1971 T100R
1970 T120
#261767 - 06/29/09 11:23 am Re: Torquing cylinder head bolts [Re: twinspin]  
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Tiger Offline
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No idea what bike you are referring to, there are different although equally valid reasons for sticking to factory torque specs depending on model.

Really simple to go to your profile and permanently add that information to your signature.


1969 TR6R
7.62 x 51 is not a maths puzzle.
#261812 - 06/29/09 2:57 pm Re: Torquing cylinder head bolts [Re: Tiger]  
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btour Online content
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Hi RR,

One reason that the head bolts loosen their torque, is the factory defect, having a too small washer, on the inner four, under rocker boxes, on some models and years. Too small and it does not distribute the load, and wears a depression in the head, causing all sorts of problems. Best to replace it as soon as possible, before the divots start forming.


Bob, Lifetime bike: '71 T120R, bought in '71 at Ken Heanes, England.
#262002 - 06/30/09 7:29 am Re: Torquing cylinder head bolts [Re: btour]  
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Blapper Offline
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The main problem is the washers are too thin not small, but are also often too thin AND too small.

You can buy the updated larger hardened washers. I moved the outer four into the inner four and had extra large thick washers made from hard stainless to cover the face of the pillars more fully:



You still have to re-torque the head as per Twinnies advice because of gasket bedding, but the never ending dishing of the head pillars doesn't happen.

Blapper redwine

#262006 - 06/30/09 8:01 am Re: Torquing cylinder head bolts [Re: Tiger]  
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RetroRod Offline
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I'll do it Tiger. Thanks for the prompt. RR


'72 Bonneville
"He who praises you for what you lack wishes to take from you what you have." - Don Juan Manuel
#262011 - 06/30/09 8:15 am Re: Torquing cylinder head bolts [Re: RetroRod]  
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dave jones Offline
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Emsworth, sunny south of Engla...
Retro- In the early 60s the torque setting was higher but it was reduced to those figures you have because of some trouble or other.

#262044 - 06/30/09 1:24 pm Re: Torquing cylinder head bolts [Re: dave jones]  
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John Healy Online content
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Retro: The 10 odd factory manuals that cover the period from 1945 to 1983 list the cylinder head torque for the 3/8" head bolts as 18 pounds (threads dry). The clamping action of the head bolts is as much about the expansion of the cylinder head as it heats up, as it is with the original torque figures. Further tightening the head bolts past the recommended figures increase the chances of damaging the aluminum, distorting the valve seats, changing guide alignment with the valve seat and distorting the cylinder barrel in the area of the head bolt holes.

With all due respect Blapper, increasing the thickness of the four inner washer alone will not increase the washer's ability to distribute the pressure on it, and the tendency to displace the aluminum under it. As the head expands with heat, the pressure, in pounds per square inch (or what ever measurement you choose to use) of pressure on the aluminum will be the same as with the original thinner washer. You will experience the same loosening between torquings.

By moving the larger outer 4 head bolt washers, 82-2184, to the inside 4 head nuts on 1971 and later 650/750 twins, you decrease the washer's contact pressure (psi), and the tendency for the small o.d. washer to displace the aluminum instead of clamping it.

We have been using the standard 82-2184 head bolt washer under the four inner head bolt nuts on 1971 and later 650 and 750 twins since it was recommended by Brian Jones in 1985. On the 750 twin we raced, whose compression was well above 13 to 1, we never had to be retorque the four inner head nuts due to cylinder head distortion under the four inner head bolt nuts when these larger, but not thicker, washer were used.

The 82-2184 head bolt washers are readily available and can be found at most flea markets or dealers. They are also very inexpensive and provide real technical value for the couple of dollars you will spend. Of course if you have a bar of tool maker's steel that can be hardened and some time on your hands there is certainly nothing wrong with making a set of hardened copies of the 82-2184 washers. Just don't forget, if you use them on the outside four head bolts they will rust if you don't have them plated.


#262058 - 06/30/09 2:16 pm Re: Torquing cylinder head bolts [Re: John Healy]  
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btour Online content
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Hi Blapper,

Nice looking head. I can still see a bit of pillar though. smile You did not work from a pattern?

I discovered that those valve inspection covers are #2 posi drive, just like the case cover ones. It fits way better than a philips. They are available from the snap on guys.


Bob, Lifetime bike: '71 T120R, bought in '71 at Ken Heanes, England.
#262065 - 06/30/09 3:04 pm Re: Torquing cylinder head bolts [Re: btour]  
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Hi John,

I think we have a mal comprendre. I did move the four 82-2184 to the inner positions, and made slightly larger diameter thick stainless washers for the outside four. I can't do more than that I think.

So far (which isn't very far at all - two re-torques), I have no displacement of the head ali at all and the weather I've ridden in has been almost 40.

Hi Bob,

Some of the pillars are not round and I drew the limit at CNC'ing them out of solid! The washers I made are bigger than the standard 82-2184 ones though.

I used the old screws and bolts to hold the head together and to the wooden plate when it was together for vapour blasting then changed them all for stainless, so those Pozi's are now allen heads.

Blapper redwine

#262072 - 06/30/09 3:39 pm Re: Torquing cylinder head bolts [Re: Blapper]  
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btour Online content
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Hi Blapper,

I know they are not round, so that is why I was ribbing you a bit. I am shocked you drew a limit! That would have been so Blapper ( that should be a new word to describe something that is totally perfect).

I am interested in how you cleaned the head. You bolted head assemby to a wooden plate? And vapour blasted? Right, what is vapour blasting? (Said like Bill Cosby in his Noah and the Ark routine. Remember that one? God says, Noah I want you to build me an Ark. I want you to build it 40 cubits by 40 cubits, and Noah, says right what is a cubit?) Zumph, zumpah.


Bob, Lifetime bike: '71 T120R, bought in '71 at Ken Heanes, England.
#262074 - 06/30/09 4:02 pm Re: Torquing cylinder head bolts [Re: btour]  
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Emsworth, sunny south of Engla...
Here is some boring info:

I had a look at Triumph service bulletin no 296 from March 1968. It states that after some testing it was found that, taking into account heat cycles, eveness and heat transfer, all aluminium headed 500s and 650s should have the head torque amended to 18 lb/ ft for the 3/8 bolts and 15 lb/ ft for the 5/16 bolts. After this I had a look at a 63 workshop manual and it gives the hefty figure of 35 lb/ft for the outer bolts and 15 lb/ft for the inner one. Another source says that it was 25lb/ft for the outer. This must have been after the 63 models. So from 68 it was officially 18lb/ ft for 3/8 bolts for any model of any year with an alloy head.

I'm sure that as everyones torque wrenches are probably out a bit so that maybe they get done at 17 or 19 or whatever but as long as they are even it is fine. You can get them recalibrated but I haven't bothered.

dave

Last edited by dave jones; 06/30/09 4:03 pm.
#262075 - 06/30/09 4:04 pm Re: Torquing cylinder head bolts [Re: btour]  
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Blapper Offline
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Bob,

Don't take the micky out of my curse - it's not nice. wink

This sort of thing:




I don't have one of the head, but you get the idea. Vapour blasting is incredibly fine media carried in suspension in water squirted at very high pressure. It gives a nicer finish (IMHO) than coarser finishes - I can't compare to soda as I couldn't find anybody who did that.

Blapper redwine

#262084 - 06/30/09 4:43 pm Re: Torquing cylinder head bolts [Re: Blapper]  
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btour Online content
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Holy smoly, Leeping Lizards, Jumping Johosofats! That is so Blapper. smile

Dig the wooden plugs made to fit the holes, even.

What did you do to those barrels? Powder coat them, and then vapour blast? Or vice versus? The black texture looks cool. Or I should say, It looks Blapper.

Allens are so passe. Torks are in. I mean who carries a tork? Keeps the gremlins out, too. All gremlins carry allens and philips, but not torks.

It so redneck round here, it makes Deliverance look like Snow White and the Seven Dwarfs.


Bob, Lifetime bike: '71 T120R, bought in '71 at Ken Heanes, England.
#262097 - 06/30/09 5:22 pm Re: Torquing cylinder head bolts [Re: Blapper]  
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Blapper Offline
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After:



redwine

#262144 - 06/30/09 8:04 pm Re: Torquing cylinder head bolts [Re: dave jones]  
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From recollection (don't have his book at work) Stan Shenton recommends increasing Triumph torque numbers by a couple of lbs-ft. Again with threads dry.

My 2c


Moderated by  John Healy 


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