Cam shaft nut

[Barnsey]

Does anyone know what torque to use when doing up the cam shaft nut C15?

[Barnsey]

The online robot suggests 35 ft lbs but I don't trust those things.  I've not found it in Haynes or Ratio yet.

[DAVE BRADY]

Hi,

35 lbs/ft should get it very tight but I think it has a lock/tab washer so a bit less would probably suffice.

Dave.

[Barnsey]

Thanks!  Hugh Ferrier used a dollop of Thread lock on his.  I don't have a lock tab washer, but I'll check out Fleabay. 

[limeyrob]

I don't think it needs to be that tight, the tab washer or Loctite help. On a modern engine a circlip would do the job of the nut.

[Barnsey]

It looks very much like you do up the nut to remove any play and then rely on the clip (and/or loctite) to hold it on.  I tightened the nut to around 30 ft lbs but it locked up the engine such that I couldn't kick it over. 

[Barnsey]

I rewatched Hugh's video https://www.youtube.com/watch?v=Kw0FfvL5Lb8.   He definitely torques the nut up tight but when I do the same it locks up the gearbox. 

[rhyatt]

You may be suffering a lack of gearbox end float.
Ie , when you do the screws up that hold the inner co er to the crankcase, it tightens up the gearshift.
Undo the camshaft nut and secure the ring of screws , all the time checking happy rotation of the gearbox.
I suspect it'll lock up even without the camshaft nut

[Barnsey]

As soon as I undo the camshaft nut it slackens off and starts turning again.

  As per previous threads,  I changed the shims and added a gasket to improve the endfloat.

[limeyrob]

Which nut do you mean?  There's no nut on the camshaft on a C15.
If its getting stiff when you tighten a nut then something isn't right.  Its all got to spin freely when assembled at room temp.

[rhyatt]

As mentioned, you don't not have enough end float on the gearbox mainshaft.
If you grab the tapered end of the gearbox shaft , can you push pull it into the gearbox ?
If yes you have end float , if not you have no end float and need to investigate where it has gone.

My end float disappeared because I hadn't pushed the output bearing into the box far enough before reassembling.

[Barnsey]

This nut, which holds the timing gear and camshaft. 

[Barnsey]

I can't get enough access to the gearbox mainshaft to wobble it now that I have reassembled it, but I was careful in changing the shim and adding the gasket to give enough end float.  That was a whole seperate sage which I have already been through. 

  With the camshaft / timing gear, nut loose everything turns over fine.  When I tighten up that nut it clamps the timing gear against the bearing and everything locks up. 

 As far as I can see the nut is there to remove the play, and Rupert Ratio suggest that you can run without that nut if the endfloat of the camshaft has been set up.

  Also, since the shaft rotates anticlockwise it won't allow the nut to work loose. 

   SO howcome Hugh is torquing his nut up?  One of us has to be wrong.   

[limeyrob]

Thanks for posting that picture, I was looking at the wrong part!  Since the later engines don't have a nut it can't be that critical. I see there is a tab washer 40-0117, does this fit into the wider slot in the thrust washer 40-106?  An odd arrangement.  I would take the cover off, put the cam in and get a measure of where the cam shoulder lies.  It should be just proud of the bearing / bush by a few thou. If its binding it must be below.  You can relive the bush slightly, it is new (I found new parts to often by out by a few thou). You could leave the nut just hand tight and rely on the tab washer and loctite but it would be nice to get the fit right.  I doubt it needs more than a few lb-feet but what I don't like is the bush will expand more than the shaft so if its tight cold it will be worse hot. 

[Barnsey]

I agree that it is an odd arrangement. Yes I bought that correct tab washer, so that will help, and the Loctite.  I think this is something I might need to revisit.   Thanks!