Torquing the crank nut

[David Mutch]

Hi folks. I'm wanting to take the timing cover off to check the condition of my timing chain and tensioner. I'm not too worried about getting the crank nut off, as I've done the job before. However, doing it back up again is a different story. On a previous boat (on advice gratefully received on this forum), I've removed the starter and jammed a tooth on the flywheel to stop the engine rotating when torquing the crank nut back up. On this boat, though, getting the starter off is a real pain, due to access. I'm wondering if there's any other way to get the nut torqued back up? Is there a hole in the bell housing where you can insert a locking pin into the flywheel like you can on some cars, for example? All suggestions welcome 🙂

 

Edited May 3, 2023 by David Mutch

[Bee]

Somewhere there will be a rotating part that you can jam by putting a piece of wood under a nut and the other end on the bottom of the boat and torquing up the crankshaft nut. Maybe stillsons on the prop shaft, maybe from under a nut on a coupling to the floor, maybe some other thingy. If you do find something be careful you don't damage anything, 

[Tracy D'arth]

Which BMC engine?

If its 1.5D 0r 1.8D there is no hole for a flywheel lockup.

But you could drill one. A 20mm hole over the ring gear.

Do not try locking the outside of the front pulley, you will wreck the harmonic balancer rubber bonding but there should be 2 threaded holes in the pulley centre, 1/4" BSF I think that you could make a bar fit with a big ring end and hole around the big nut.

[David Mutch]

1 hour ago, Bee said:

Somewhere there will be a rotating part that you can jam by putting a piece of wood under a nut and the other end on the bottom of the boat and torquing up the crankshaft nut. Maybe stillsons on the prop shaft, maybe from under a nut on a coupling to the floor, maybe some other thingy. If you do find something be careful you don't damage anything, 

Thanks, but I've got a hydraulic gearbox, so the prop shaft won't be engaged without the engine running. About the only things that might work are the water pump and alternator, but I don't suppose you'd get a valid torque reading with the belt on, and I'm not sure if the belt would provide the necessary friction.

55 minutes ago, Tracy D'arth said:

Which BMC engine?

If its 1.5D 0r 1.8D there is no hole for a flywheel lockup.

But you could drill one. A 20mm hole over the ring gear.

Do not try locking the outside of the front pulley, you will wreck the harmonic balancer rubber bonding but there should be 2 threaded holes in the pulley centre, 1/4" BSF I think that you could make a bar fit with a big ring end and hole around the big nut.

Not sure about drilling the bell housing. The holes in the pulley centre might be a good shout though. Thanks 👍

[MtB]

How about removing an injector and filling a cylinder with oil, and put a scrap injector in to plug the hole? That would give you 20 minutes at least to torque it up before the oil squeezed past the rings. 

 

Just wondering. Probably a good reason why this isn't a standard suggestion. 

 

 

Make sure the crank is in a good position, i.e. about half way between TDC and BDC.

 

 

[john.k]

Get a flogging spanner and hit it with a 7lb sledge a couple of times ......thats all the torque youll ever need,.

[David Mutch]

7 hours ago, john.k said:

Get a flogging spanner and hit it with a 7lb sledge a couple of times ......thats all the torque youll ever need,.

Not sure I'm brave enough for that approach!

8 hours ago, MtB said:

How about removing an injector and filling a cylinder with oil, and put a scrap injector in to plug the hole? That would give you 20 minutes at least to torque it up before the oil squeezed past the rings. 

 

Just wondering. Probably a good reason why this isn't a standard suggestion. 

 

 

Make sure the crank is in a good position, i.e. about half way between TDC and BDC.

 

 

Thanks, but on the whole, removing the starter sounds easier!

[john.k]

What if you break a ring gear tooth?.......make the flogging spanner seem like a better idea?

[Tracy D'arth]

52 minutes ago, john.k said:

What if you break a ring gear tooth?.......make the flogging spanner seem like a better idea?

You would never manage to do it, the radius on the flywheel compared to the bolt means that very little torque needs to be applied to the ring gear to counteract the torque on the bolt.

As for causing a hydraulic lock on one cylinder, with the engine cold the piston rings gaps would quickly let the oil down into the sump.

The only other way would be to wind the  valves open and let the piston rest on them but its brutal and risks bending valves.

I think drilling the flywheel housing is a good bet. In fact drill at an interfering angle and tap for a 12mm bolt and you have the answer for all time.

I have occasionally flogged the bolt tight and got away with it but its not good practice, especially if its a 1.5D with a 3 bearing crank. By the same token I have used the starter and a long spanner to undo crank nuts but its a scary thing to do. 

Edited May 4, 2023 by Tracy D'arth

[Quattrodave]

Rattle guns are great for this...

[MtB]

34 minutes ago, Quattrodave said:

Rattle guns are great for this...

 

Can you set the torque on them, then?!

[Tony Brooks]

2 hours ago, Tracy D'arth said:

By the same token I have used the starter and a long spanner to undo crank nuts but its a scary thing to do. 

 

I am sure Austin/BMC listed a special tool for doing that on the A series petrol engines back in the day. I think your two pin tool was also listed for some engines.

[BEngo]

41 minutes ago, MtB said:

 

Can you set the torque on them, then?!

Yes, if you buy a good one.  If you buy a a cheap one it is wise to check the setting against an Acratork or similar.  The makers tend to have a relaxed view of caribration.

 

N

 

[Tracy D'arth]

2 minutes ago, BEngo said:

Yes, if you buy a good one.  If you buy a a cheap one it is wise to check the setting against an Acratork or similar.  The makers tend to have a relaxed view of caribration.

 

N

 

I used to have a selection of quill shafts that set the torque limit off an air wrench. Our garages used them to stop the tyre fitters from over tightening customers wheel nuts. Did not have one big enough for the BMC crank bolt though!  30mm if I remember, its been a while. Calor spanner fits I think!

[MtB]

2 minutes ago, Tracy D'arth said:

Our garages used them to stop the tyre fitters from over tightening customers wheel nuts.

 

 

Ah yes, that's the sort of rattle gun I was thinking of! 

 

Last 20 years or so though, I notice tyre fitters actually switching over to a proper long-handle type clicky torque wrench for final tightening. 

 

Probably needed to when alloy wheels became common. 

 

[Tracy D'arth]

7 minutes ago, MtB said:

 

 

Ah yes, that's the sort of rattle gun I was thinking of! 

 

Last 20 years or so though, I notice tyre fitters actually switching over to a proper long-handle type clicky torque wrench for final tightening. 

 

Probably needed to when alloy wheels became common. 

 

When I was on the tools, most of the wheels were wooden...............................................................................................

[MtB]

3 minutes ago, Tracy D'arth said:

When I was on the tools, most of the wheels were wooden...............................................................................................

 

And had they discover by then that the best shape was 'round'?!

 

 

 

 

 

[Mikexx]

1 hour ago, Quattrodave said:

Rattle guns are great for this...

 

I confess I have been wary of using a rattle gun where there is a chain involved.

 

When I have removed and replaced a crank-bolt I have always taken out the starter. The ring gear should be pretty strong. It has to put up with the hammering action of the starter pinion.

 

While there are two small bolt holes on the pulley, you would have to make up a tool to bolt to the pulley or your studs or screws would simply bend after supplying the sufficient torque to undo the crank-bolt.

[Tracy D'arth]

I too would not use an impact wrench on it. 

Though flogging it down is not much different.

I would use one for tightening a head down though.

[David Mutch]

Thanks to @Tracy D'arth's tip about the holes in the pulley centre, I've ordered one of these. Will let you all know how I get on with it 🙂 

[Mikexx]

14 minutes ago, David Mutch said:

Thanks to @Tracy D'arth's tip about the holes in the pulley centre, I've ordered one of these. Will let you all know how I get on with it 🙂 

 

From what I remember the area of pulley with the holes mentioned are recessed such I'm not sure that tool will work?

 

Do let us know how you get on with it as it saves a lot of faff removing the starter.

[David Mutch]

8 minutes ago, Mikexx said:

 

From what I remember the area of pulley with the holes mentioned are recessed such I'm not sure that tool will work?

 

Do let us know how you get on with it as it saves a lot of faff removing the starter.

You may have a point there. It's recessed 20mm, which is probably about the length of the pins. I guess I may be able to bend the tool a bit if it doesn't quite reach!

[Tracy D'arth]

I hope that works for you, it may need to be bent a bit to fit.

 

A word of caution.  When refitting the pulley, ensure that the woodruff key is correctly fully located in the crank and neither end is sticking up. Else when you fit the pulley by hand only, not wound in with the bolt, you can burst the keyway in the pulley, and they are expensive.