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3818 Posts in 1183 Topics- by 2192 Members - Latest Member: mariodea

February 09, 2012, 08:22:57 AM
Maintenance IssuesTR4 Rangeconnecting rod bolt problems?
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Author Topic: connecting rod bolt problems?  (Read 693 times)
JohnB
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Posts: 11



« on: September 02, 2009, 07:15:05 PM »

I am in the process of rebuilding a TR4 engine to put in my TR2 and have been using the "Haynes TR2-TR4a Workshop Manual" and an original factory "TR2 Service Manual".

All has gone well so far, but I may have hit a snag.

In the "How to Restore Triumph TR2,3,3a" by Roger Williams, he states there are two types of connecting rod bolts, which I knew. What is news to me is that the ones used without locking tab washers are called "stretch bolts" and should never be re-used.

My 2 manuals say nothing at all about not re-using the non lock tab bolts, and WILLIAMS doesn't explain why not, but simply says "obviously it's essential that the stretch bolts are never re-used". Am I to assume these type actually stretch, get longer and do not return to their original length but retain the stretch? So they can't be re-used even with locking tabs?

Why doesn't Haynes talk about this? Help!!!!!!

John
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TR3driver
Full Member
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Posts: 233



« Reply #1 on: September 02, 2009, 10:12:28 PM »

In a word, I believe Mr. Williams is mistaken. 

Normally, the TR3/4 rod bolts can be reused unless they have been damaged. The only difference between the "lock tab" and non-lock tab versions is the length.

In fact, most engine builders recommend leaving out the locktabs even on earlier engines that originally had them. It turns out that the tabs can actually allow the bolts to loosen, because the tabs themselves are soft enough to permanently deform under severe conditions. However, if you do this, check to be sure the bolt doesn't bottom out in the rod.

Since the stock bolts are not undercut, the weakest point (where they will stretch if overloaded) is the threads just outside the rod. One way to check is to spin a nut down the threads and see if it binds before reaching the bottom.
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Randall
58 TR3A TS39781LO :(now totaled Sad
56 TR3  TS13571L daily driver
71 Stag LE1473L waiting for engine rebuild
71 Stag LE2014LBW waiting for 4-speed rebuild
charley fitch
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Posts: 335


« Reply #2 on: September 03, 2009, 01:50:02 AM »

One further piece of information is that the early bolts and tabs were used on engines up to CT34071E and the "stretch" bolts were used after that.  The connecting rod assembly also changes with the same engine numbers.  So this would tell me that there is a difference in the rods where the bolts are going to go and the different bolts would be needed.
Charley Fitch  Cool  Roll Eyes
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JohnB
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Posts: 11



« Reply #3 on: September 03, 2009, 12:12:25 PM »

Does anyone out there have a Factory Service Manual for the TR4 that they could look into and see what the factory said about this bolt dilema?  (to replace or not to replace)

Opinion seems to be that Haynes is "a bit" lacking in info, and I only have a TR2 Factory Manual. (TR2s used lock tabs)

John
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JohnB
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Posts: 11



« Reply #4 on: September 03, 2009, 12:20:43 PM »

Actually that needs to be for a TR4a model not TR4.
The engine I am using is from a TR4a. (CT52879E)

thanks.... John
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