Camshaft bolt reuse

[mh007]

As said, for the cost of the bolt, why would you want to take the chance?

Personally, I renew them every time.

Oh & the same goes for K-Series head bolts.......why take the chance after all that work considering the cost of a new set?

[kaiser]

Originally Posted by mh007

As said, for the cost of the bolt, why would you want to take the chance?

Personally, I renew them every time.

Oh & the same goes for K-Series head bolts.......why take the chance after all that work considering the cost of a new set?

Engineering is about NOT taking chances, and by knowledge using materials to their best possible use.
Any fool can buy new every time, but it takes knowledge and skill to know when to do what.

In this case it is safe to re-use.

[Mike Noc]

Originally Posted by beinet1

Re-using bolts that have been torqued to yield, will in most cases work. That is clearly explained in the link above.

Assuming that they haven't been severely over tightened during any previous work of course.

[mh007]

Originally Posted by kaiser

Engineering is about NOT taking chances, and by knowledge using materials to their best possible use.
Any fool can buy new every time, but it takes knowledge and skill to know when to do what.

In this case it is safe to re-use.

First things first: I don't appreciate being called a fool so you can put a stop to that straight away!

45yrs in the motor trade & still going proves that I think!!
That includes engineering so I am fully aware of when or when not to replace.

When I have to carry out work on customers cars & new bolts are specified (especially internal engine bolts), that is exactly what I fit. I have to provide a warranty with all my work & I quite happily do that knowing that I have done the best job possible.
I do exactly the same on my own vehicles & always have done.

My whole being that for less than £5 for a camshaft sprocket bolt on a KV6, why not replace them when they are specified?

Of course, all the above is just a matter of personal choice.

[beinet1]

Originally Posted by mh007

When I have to carry out work on customers cars & new bolts are specified (especially internal engine bolts), that is exactly what I fit. I have to provide a warranty with all my work & I quite happily do that knowing that I have done the best job possible.
I do exactly the same on my own vehicles & always have done.
Of course, all the above is just a matter of personal choice.

I am 100% supporting this

[p2roverman]

I've commented before in that I think there is a problem with the new camshaft bolts being supplied (made by Poonaforge in India). The thick washers that come attached have a small raised lip on one side, depending on which way the washer is on the bolt, this lip will contact the face of the belt-wheel first. I am convinced that this causes an incorrect tension on the bolt when the 27 Nm toque is reached before tightening a further 90 degrees. As a result we have no idea just what the clamping force generated is.

The solution would be to grind off the lip on the washer before use, but my preference would be to reuse the original British manufacture bolt provided its history is known. However, as the bolt has been used and stretched by design, the official torque and turn setting no longer applies.

My question is roughly what torque should be applied when re-using these bolts. Several of the experienced guys here reuse these bolts so what's your advice in these circumstances.

[kaiser]

Originally Posted by p2roverman

I've commented before in that I think there is a problem with the new camshaft bolts being supplied (made by Poonaforge in India). The thick washers that come attached have a small raised lip on one side, depending on which way the washer is on the bolt, this lip will contact the face of the belt-wheel first. I am convinced that this causes an incorrect tension on the bolt when the 27 Nm toque is reached before tightening a further 90 degrees. As a result we have no idea just what the clamping force generated is.

The solution would be to grind off the lip on the washer before use, but my preference would be to reuse the original British manufacture bolt provided its history is known. However, as the bolt has been used and stretched by design, the official torque and turn setting no longer applies.

My question is roughly what torque should be applied when re-using these bolts. Several of the experienced guys here reuse these bolts so what's your advice in these circumstances.

It has not been stretched permanently.
If you operate in the elastic range, the bolt reverts to its original size when undone. You are definitely operating in the elastic range here.
The bolt thus behaves exactly like a spring and complies with Hooke's law of elasticity.


Just fit the bolt, tighten to spec and relax.

[SD1too]

Yesterday I removed my front camshaft sprocket bolts. I know that my engine is as it left the factory because I am the second owner and I have all the service invoices from new.

There was no thread locking compound on the bolts. I examined them very carefully and there was no evidence of any deformation. Under a watchmaker's glass the threads looked exactly like the new bolts I have bought to replace them. I conclude that they have not been taken into the 'plastic' range. I'd say that the official advice to renew them is precautionary.

Simon

[p2roverman]

THanks to Kaiser and SD1too for your comments. This make three of us that think that although the bolt is being stretched, it is still in the elastic range, so reuse should not be a problem so long as it has not been abused by overtightening before.

I'll now be quite happy to reuse original bolts, as others do. When I use the new Indian bolts I will check the washer and grind off the lip if necessary as I'm sure its presence results in incorrect tightening.

Re threadlock, its use on these bolts is not specified, so should not be used.

[p2roverman]

Originally Posted by Mike Noc

The camshaft bolts are angle tightened so are yielding when used. Probably enough safety margin in them to cope with being re-used, but of course you don't know how many people before you have thought the same.

Certainly a conflict of opinion over camshaft bolts in the elastic range or beyond.

However, my original question concerned the quality of the currently supplied new Indian-made bolts. If I want to re-use the original English bolts, previously used once, suggestions on what to torque them up to? Because they have been used and stretched as a result of use, I feel that the low torque plus angle turn method is no longer applicable, so my question to the guys that re-use camshaft bolts is "what do you torque them to?"