How do I undo this nut?

[Mr Don]

I am starting to strip down a moggy engine. But try as I might I cannot loosen the big nut/starting dog on the main pully.

Any ideas?

I have jamed the cranck. hammered back the security locking washer and using a cracking bar, but it will not budge.

[ASL642]

Does the nut have a tab? If it has this needs to be knocked back first. Try either a large adjustable spanner, ring spanner or a Stillsons. 3/4 Whitworth long spanner fits

[cadetchris]

accoring to the morris bible (the workshop manual) the thing should be torqued down to 70 lbs, so that combined with the years of use, it will be quite hard to shift.

i found that using a 3/4 Whitworth long spanner and a hammer to bang the other end does eventually loosen it, but it takes some doing

[bmcecosse]

Take care - it's possible to bend the end of the crankshaft.. The easiest way by far is to use the starter motor to do the job - never fails, and since it's a twisting motion through the crank there is no risk of bending it..... With engine out you could still use a starter - but would need to secure the engine to a bench etc - and make sure the spanner/adjustable (whatever you use) can't go flying through the air..... Otherwise - if it won't free with 'gentle' hammering, I suggest applying some heat to the dog - let it soak through - then cool the dog with blast of water - then try again!

[MarkyB]

If you only have the car in gear as a way of stopping the crank turning you could whack it till the cows come home.
The force of your blows will be dissipated all through the drive train and have little or no effect on the pulley nut.

If you cant use the starter motor you need to take the sump off and jam a bit of timber, 4x2 or bigger, between the crankshaft web and the inside of the block.
This will concentrate more of your energy where it will do some good.

[simmitc]

If using heat, watch out for for the rubber oil seal....

[bmcecosse]

It's going to need renewing anyway........

[IslipMinor]

Mr Don,

Where are you located? Could you take the block to a workshop with an impact gun? Either a 3/4" BSW or 1 5/16" AF socket will work. Does the job in seconds, engine in or out! If you are anywhere near Oxford, bring it here and I will do it for you.

[Chris Edgar]

Impact gun (electric or pneumatic) was the only way mine would come off once the engine had been removed.
As Islip Minor says, only took a second.

[mogbob]

Heat treatment works for me...boil up the kettle and pour slowly over the nut.Might need a second application but it's been first time lucky for me on two engines.
Bob