Camshaft nut torque

[UKlittleguns]

Hi Everybody,

I am rebuilding a 1957 A7 Engine.  The crank case is now all assembled.  I think torque settings are important for critical parts but BSA and other manuals are no help whatsoever.  I wonder what the community view might be about:-

1.  The Torque figure for the camshaft nut.

2.  The best way to hold the shaft while the nut is tightened.

Regards to all.

[morris]

65 lbf-ft comes to mind.
I just use a pneumatic rattle gun. Never had one come loose

[Seabee]

That seems like a lot for a camshaft nut?

[RDfella]

Presuming you meant the crankshaft nut, if the cylinders are not on you could jam the crank with a piece of wood, otherwise you're a bit stuck. Trying to resist rotation by using the sprocket is a waste of time, as the shock absorber will nullify any torque readings as the cam forces the nut outwards. Which is why I prefer tightening the nut with a hammer and drift. Others, as stated, use an impact wrench. The latter worriy me as one's never too sure what torque is being applied - one reason I never let garages use them on my vehicles. I prefer to do it myself and take the wheel to them. You'll find two distinct views on how best to tighten the crankshaft nut!

[Swarfcut]

 That's far too tight for that little nut. We are talking Camshafts?

 A bit late now but contrary to the official assembly instructions, Service Sheet 208, the camshaft and its drive gear can be assembled into the timing side case before the cases are joined.

   Make sure the locating key hasn't moved back to gouge the face of the bush, and that the camshaft gear front face is above the end of the plain part of the shaft. Other way round and the gear isn't going to get tightened against the cam and the drive will be through the relatively weak key alone.

  The cam can be easily held still with an adjustable spanner, padded if you are fastidious with a piece of card or similar. Then tightening the nut is easy.

 With the cam already in place, the same trick is preferable to blocking a lobe against the crankcase, as your enthusiasm is more than a match for somewhat weaker 60 year old alloy. Finding a suitable spanner is the hard part. It needs to restrain the cam but put no load on the case to avoid damage.

 With no official torque setting, Loctite on the threads, plus the tab washer, then a good firm nip up usual for that size of nut should be fine.


 I see this is your first post. Head on over to the intro section and tell us how you  got into this mess.

 Welcome along

 Swarfy.

[morris]

That seems like a lot for a camshaft nut?

Yeah sorry... Wasn’t wearing my glasses...
Heading back to my corner...

[Swarfcut]

    Morris, no need to apologise. You will probably be proved right!

 Maybe it's me that barked up the wrong tree, we just need a second confirmatory post from our new member.

 When you think about it, the crank nut bottoms on the drive sleeve, and that high torque value matches the combined resistance of the sleeve and cush drive spring.  So its academic really, for crankshaft sleeve cush nuts it just has to be *uck*ng tight.*

Swarfy

  * Other more precise measurements of tightness are in modern use.

[berger]

as has been said the camshaft nut has a lock washer  I leave it until all the gears are on and put wood dowel through the little end eyes and rest it on the crankcase mouth.

[chaterlea25]

Hi All,

the camshaft and its drive gear can be assembled into the timing side case before the cases are joined.

This is my preferred way to start building the engine, It means you can hold the drive end of the cam in vice soft jaws and fit the key and pinion, then tighten the nut, I go to 35 ft/lbs or so
If the cases are together and the cylinder off, a piece of alloy can be used to wedge the cam towards the timing side so the key does not gouge the bush, 
I just looked at Beeza's post where the cylinder is in place and no cam gear fitted   

Keep Safe
John

[berger]

probably fit nut holding crankshaft drive

[chaterlea25]

Hi Berger
The problem is to get the gear onto the cam without  knocking the key into the bronze bush
the cams will slide in about 1/8th of an inch without the gear.
The gears can be a very tight fit on the cam

John

[UKlittleguns]

Hi Everybody,

Thanks for all your replies.  I am going to set my camshaft nut at 40 ft. lbs.  This is based on standard bolt torque tables for fine threads and half nuts.  If the wheel falls off I'll let you all know but at least it will be a known value from which to progress.  I'll check service sheet 208 but it doesn't sound like an option on an assembled crankcase.  I'm a tool maker by trade (retired) and it took about an hour to make the key fit like a Swiss watch.  I have the scars on my back from jamming gear teeth and cam lobes against other gears or against aluminium castings.  I've made up a cranked C spanner that bolts to the cam gear to resist the tightening torque.  Tried to attach some pictures but the post was rejected for being too large.  Obviously a different subject but can anybody tell me how to do it if it's possible?

Regards to all.

[morris]

Tried to attach some pictures but the post was rejected for being too large.  Obviously a different subject but can anybody tell me how to do it if it's possible?

If you are using a Windows pc, the easiest way is by using the Paint app which is a standard feature on your pc.
Step by step explanation here;
https://www.wikihow.com/Resize-an-Image-in-Microsoft-Paint
My original pictures are usually around 1.5 Mb, I reduce them to 40% which leaves them still big enough to see the details.
Glad to be of any help...