next »

[JohnB]

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

[TR3driver]

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.

[charley fitch]

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   

[JohnB]

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

[JohnB]

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

thanks.... John