Britbike forum Forums British Motorcycle specific Brands Triumph bulletin board Retorquing of the T120 cylinder head

Hi John,

What would cause the center head bolt, the litte one, to be loose on second re-torque, if it were fine on first?

Sigh, He must have gone back to the safety of his log. Trying to catch up with him, is really hard.

RR, Don't skimp on this. It is not that time consuming. Have a tool made so you can get in there with rockers on.

This will be a considered option. The easier it becomes for this old fellow to retorque, then it will be so much more likely that it will be done. . I must say though that I am now very interested in finding out if I can get away without the re-torque. RR

Thank you a lot JH for you valuable time and advice.

As the Klinger head gasket appears to be of compound manufacture, the Bulletin seems most relevant to this type of gasket. Suffice to say that your expereince and advice, and that of others, is highly likely to be right, I think I will throw caution to the winds and see how I go with a single torque down. I will advise what happens. Catch you next time. RR


PS. Did the tenth headbolt and the klinger head gasket really fix the leaking head gasket problem??

Not sure, but using the larger, inner head-bolt washers, correct PRT O-rings and re-torquing the head will!!

Steve

To add to what John Healy said- The early unit engine manuals show 25 lb /ft recommended for the 3/8 bolts. I have a 66 specific manual and it is shown in there. It was later amended to 18 lb/ft and this is the setting you should use on all unit engines. This is where the cofusion arises. 25lb/ft must have turned out to be too tight.

When I had a 3TA as a teen I used to borrow a torque wrench to do the head. I didn't know you had to retorque and it would be leaking after a short time. I do retorque now until the bolts stay the same. The outer ones are usually just about ok but the ones that go through the rocker boxes are always loose.
Dave

Hi RR,

It is nice of you to use your bike in this experiment, and let us know what happens.

Be aware though that it is more than the head gasket that you might lose. I was once shown an extremely mashed piston, and was told it was the result of carelessness in not retorquing. The opinion was that the air leak therein resulting did the damage.

So, I guess there was one earlier manual (edited to reflect reality) with the higher 25 torque figure?

Two thoughts come to mind.

1) Engine heat provides the real effective clamping force.
2) John once provided a story, of how, when the Brits, departed the plane and were on the Tarmac, they were atonished at just how Hot it gets in the U.S.

Probably unrelated. Most defintely not related. Why the 25 figure happened is a mystery.

One thing that probably should be kept in mind, is the human tendancy to think that if enough is good, than more is better, or overtighten in an attempt to not repeat re-torquing later. I know at least one engine re-builder who told me to torque into the 20's.

Don't anyone look at me. I'm here as a student myself !

Just to be clear and up to date:
If the composite gasket(Klinger) was introduced to prevent failures with the copper gasket, why is everyone seemingly still using copper ?
Did the composite type fall out of favor for some reason?
T.I.A
[Thick Irishman Asking]

Well, no but that's not my point here. The 1963 unit manual shows 18 foot pound as did the non-unit manuals before it. It is just the 1966 manual that shows the 25 foot pounds. As you say, this was corrected in a Service Bulletin to 18 foot pounds. manuals for unit 650 models after the 1966 show 18 foot pounds.

The point I would like to make is: Just having a Workshop manual or parts book for the year you are working on does not make you an "expert." You need all of the update information, usually in the form of addendum sheets or service bulletins, to just get started.

Then you also need to have accumulated all of the information where a part number was used for more than one condition. I know Stuart believes that Triumph never did this unless the part was backward compatible. This was not always the case as I have stated before. While a lot of the differences were inconsequential, and only worrisome to restorers, there are iteration changes that can cause serious problems. To quote Geoffery Robinson, advisor to the Worker's Co-operative, who advised dealers, "We don't care... we don't make 650's any more" when queried that a lot of co-operative 750 part numbers were not in the original specification and would not work in the 650.

A link on this forum brought me to the Triumph Forum and a thread listing the Triumph twin balance factor is 50% and a picture of a hand grenade, oh, I mean flywheel. It had holes a small animal could live in all around the face of the flywheel. And everyone was listening to this thread intently... There was no Stuart, or RF to bring this thread around to reality.

Now we might not all agree, get facts correct (we all do it), but we have collected a group of pretty sensible members who will bring the discussion on center. We even have Stuart, who keeps us all sober, and on subject. Thank you Stuart, you are appreciated more than you know. We also have RF, who brings a wealth of knowledge, and a Celtic "twinkle." Whately: an Old Celtic word meaning 'high' or 'noble' And yes. PeteR who brings a wealth of experience which he is willing to share. Yes, there are others to numerous to mention.

Now I must emphasize, we don't all agree, we don't all "follow" the Workshop manual or Service Bulletins, but we do our best to try to share what we have learned. I have three, 3 draw storage cabinets full of Workshop manuals, Service Bulletins going back to the late 1940's from Triumph, Johnson Motors, and The Triumph Corporation in Baltimore. Been working on the same motorcycle since 1959, and there isn't a day where I learn something new (or re-learning it as age requires).

Even Bob (btour) who just keeps asking questions has taught me that you can modify the 1971 head bolt arrangement to the T140 specification. I pushed back at first, but you know an old dog can learn new tricks.



Mostly because it has taken over 30 years for owners and mechanics to come to grips that the original small inner head stud washers just don't work. If left in place the copper holds up better and will not blow out when the 4 inner stud nuts come loose, come loose, come loose. Most went back to the copper out of frustration
John

Hi Pete R,

This is a question on re-torquing that I asked many times in the past and never got an answer. So I would like to thank you for that answer.

Of course, I am a bit confused again. If you back off first to break the striction, then how would you know what you had in the first place for torque. IE. how would you know if the the torque was stable?

Check your valve clearances before you re-torque?

I always do, just out of curiousity to see where they were, and to see if I guessed right . And if they are close and no retorquing occured, then I am done.

And lately, I have a new drill, to get as many valves closed as I can, to relieve any added pressure before re-torquing (hey maybe that is why the center bolt re-torqued). Way too OC, huh? WOC or Way too freakin Anal, (WTFA)

But I was a bit of freak about valve clearances. Which was demonstrated to me, when the cap on the end of rocker spindle disappeared. I rode it and it went well. And that was with variable valve lash. Of course I may have been too busy burning my finger, holding on the hole in a vain attempt to limit the bleeding, to really notice how the engine was performing.

If you are curious about the delta (before and after), use a fine tipped marker to place witness index marks. Typically, you will see after retorquing that the witness mark will have advanced beyond the starting point. Knowing the thread pitch and estimating the angle of advance, you can actually calculate the dimensional change for the torque level. In an ideal world you would be measuring bolt stretch... just not practical in this application. Good practice is to retorque. Can you get away without doing it? Maybe... sometimes. There are many steps in life, Grasshopper, that you may skip. But you may not be able to skip the consequences of skipping them.

Don

Best one iv'e heard yet, but watch out for those ropes and knots!


edit to correct quote

Bob,

I too have to thank Pete for that tidbit.....will come in handy very shortly....

Perhaps using an old-time-y torque wrench with dial readings in both directions would tell you the info you're seeking?



Steve

Jubee, that won't work since when loosening, you're measuring resistance of static friction, when tightening, you're measuring bolt stretch mostly.

Thanks Bob,

Yes, well I could just follow the good advice here, but it is a bit of an experiment too. I am modifying my ideas all the time and later this week, when all is done, I will report back. At the moment I have moved one step closer to Dr Healy's position and willdo one retorque after the initial engine run.

I also have in mind some radical views like greasing the head bolt threads, oiling between the head bolt and the washer prior to torquing, and increasing the torque on the 3/8 bolts to 25ft/lbs and the 5/16 bolt to 18ft/lbs

I am even considering a tenth bolt hole, or alternatively a plate on the ninth to cover an area where the tenth would go.

And so it goes on. RR

[quote

Don't anyone look at me. I'm here as a student myself ! [/quote]

C'mon Richard, you'll have to comment on this!!

Attached photos of progress to a new era in dependable Triumph engines.

http://i543.photobucket.com/albums/gg474/RetroRod/10Hole650head.jpg

http://i543.photobucket.com/albums/gg474/RetroRod/10holeretainingplate.jpg

http://i543.photobucket.com/albums/gg474/RetroRod/10holetopsideview.jpg

With skill, my friend and bro-in-law Jeff (the uninitiated) has drilled a tenth hole in the 650 head. Jeff and I have exhaustively discussed the problem, examined the old parts, and have concluded that we needed to come up with an approach that was "outside the square", that we believe will be a solution to the problem of leaking head gaskets on these old tarts.

Jeff has also manufactured a retaining plate, that we believe may go toward an improved seal of the head gasket, particularly during the initial startup, until the the engine reaches operating temperature.


Jeff raised with me a question as to the causation of this leaking head gasket and then referred himself to the gasket in question, that spoke several things to him.

It seemed apparent from the gasket that the head bolts had not been loose (it had been retorqued on three separate occasions and the gasket verified this). After some discussion between ourselves, and yourselves, there was no obvious explanation as to why the gasket leaked where a tight bolt was in place. Thus our decision to implement this novel fix.

In addition, the decision to implement this significant modification was partly due to the the notion that the usual method of fixing the head down potentially introduces some distortion. We are also of the view that the PRT crush is very, very critical. On the previous occasion of fitting this head I was happy that the .050" obtained on that occasion,was OK. We have rethought this, and we now believe that .030" is nearer the mark. We feel that this clearance will greatly reduce the likelihood of bowing the head when torquing down.

We understand that it is impossible to predict the results we may get, however, we also believe that we need certainty when replacing a head, so that owning an old Triumph gives us more riding time(pleasure) than down time. So, thus this effort on our part. RR

As Duke said, if the bolt turns farther clockwise than it was before you loosened it, then it needed re-torquing.

Hi Triton Thrasher,

I see. Thank you. That would work. A bit difficult with the inner head bolts though, if done through rocker boxes.

If PRT optimal crush is .030"- how do you achieve it? In my selection of PRT square O rings the smallest is way too thick. Where do you source them? I recently saw a U-tube video of a Brit, I think, using a regular O ring there because he couldn't get to .080" any other way. He also opines the square ring is not so much an oil seal as a "cushion" (?).

In another video he puts a "71 rocker cover together with the Thackery washer next to the rocker, which J.Healy tells us is a factory shop manual error- can block or divert the rocker oil feed
Doug

Thanks for the info hh....I am certainly no mechanical engineer (nor ANY engineer for that matter ).

Cheers,

Steve, who's waiting for his thread-lock to cure....

You guys with your modern-fangled bikes!