Topic: re-usability of torque screws

[_mark]

Hi all. I'm rebulding the engine of a 750 K1.
I heard somewhere and in this video that the screws of the connecting rods cannot be tightened more than one time (if I understood correctly) because they become stretched to yield after first time.. I didn't found such info in the shop manual.

@time 2:58  & 15:09

Is that true ? I didn't found it in the shop manual. Are there any other bolts in the engine that are like these (0ne time only and to be replaced) ?

How can I proceed to check the clearances of connecting rods?

Thanks and Regards.

[bryanj]

They are fine to reuse as long as they are not overtorqued.
Some engines usetorque to limit bolts but these are usualy tightened by angle not torque

[_mark]

They are fine to reuse as long as they are not overtorqued.
Some engines usetorque to limit bolts but these are usualy tightened by angle not torque

Thanks. Considering that the story of my engine is unknown, is possible to determine if they have been overtorqued  ? thanks.

[bryanj]

Not really, does it look like the caps have been removed before?

[_mark]

Not really, does it look like the caps have been removed before?

do you mean the nut? 
the seem to be never touched.

[DaveBarbier]

If they are over torqued then they have been stretched. If they’re stretched then the thread pitch will change. If a nut threads down the entire diameter of the bolt then they’re fine to use again. I remember a post in the past couple months saying that the connecting rod bolts are NOT one time use.

[DaveBarbier]

Not really, does it look like the caps have been removed before?

do you mean the nut? 
the seem to be never touched.

Bryan is talking about the con rod half circle cap that is stamped with 45 in your picture.

[DaveBarbier]

And there are no other bolts that I know of in these engines that are torqued to yield. Even the head studs/bolts are fine to reuse assuming they’re in good shape and not rusted to #$%*.

[rotortiller]

What you have to ask yourself is does the engine employ stretch bolts. If it did use stretch bolts the manual will tell you the fasteners are a one time use. Lots of shop manuals on line for you enjoyment.

[_mark]

What you have to ask yourself is does the engine employ stretch bolts. If it did use stretch bolts the manual will tell you the fasteners are a one time use. Lots of shop manuals on line for you enjoyment.

Yes, that I told in first post. There are a lot of rumors about this issue but in the shop manuals I checked there is not any reference about this. Thanks

[Jerry Rxman Griffin aka MuthaF'er]

Put your torque wrench on it and see what the numbers are

[rotortiller]

Reuse the hardware, it's what is normally done with that engine.

[jakec]

I was testing bearing clearance which requires that you torque them. One of min overstretched and broke (kept spinning before reaching target torque value and eventually snapped). So I replaced all 8.

If you're worried about it and taking connecting rods off, just see if they reach the target number. If so I would think they're good?

[_mark]

If you're worried about it and taking connecting rods off, just see if they reach the target number. If so I would think they're good?

target number is 20 Nm pretty low number isn't it? I would say that who damaged them ,reached far high number but it's only a guess.

[bryanj]

It is easy to see a bad bolt as the threaded portion tends to get "waisted" as it is the narowest part