MG-Cars.info

Welcome to our Site for MG, Triumph and Austin-Healey Car Information.

Parts

MG parts spares and accessories are available for MG T Series (TA, MG TB, MG TC, MG TD, MG TF), Magnette, MGA, Twin cam, MGB, MGBGT, MGC, MGC GT, MG Midget, Sprite and other MG models from British car spares company LBCarCo.

MG MGB Technical - Problems removing cambelt pulley

Hello,

I am stripping my mgb engine down and for some reason cannot remove the bolt securing the cambelt pulley to the crankshaft. I've released the tab washer, but the bolt cannot be removed even with enormous amounts of pressure (much higher than the required torque setting). Are there any other fixing points, it seems ridiculously stiff. Does anyone have any tips how to get this removed.

Many thanks
Alex Davies

Alex,

You should not apply a high torque to undo the crankshaft pulley nut. This requires the engine to be locked in position to apply the torque. This can be damaging to internal engine components.
The Workshop Manual shows the correct method. The nut shold be undone by shock alone, with the engine rotating parts not restrained.
Attached to this message, and the next message, is the correct method.
If you do not have the special tool any other tool that fits will be OK.


Mick

M F Anderson

Alex,

The second image attached.
This does not show the crankshaft nut removal as it is not shown in the Workshop Manual, but the same method should be used on the crankshaft nut (starting dog).
I will attach an image to a third message showing the spanner used on the pulley nut of a MGA.


Mick

Mick

M F Anderson

Alex,

An image is attached showing the method of undoing the crankshaft nut on a Twin Cam MGA.


Mick

M F Anderson

Thanks for your response, I have followed a workshop manual which suggests you place a block of wood between one of balance weights (on the crankshaft) and the side of the block (to stop it rotating) Then it says to use a spanner/socket and a hammer, sadly this will not budge. Therfore I tried applying large torque (as you said, not recommended so won't do again. Any tips?
Alex Davies

I guess you have the engine out of the car?

I see no problem in applying toque to the bolt, the main issue is holding the engine still while you do so.

Best and easiest way is to spin the engine using the starter motor - even out of the car, rig up the starter to a battery and place the socket on the crank nut, arrange the handle so it is about 6 inches off the floor and spin the starter, the shock will free the bolt.
Chris at Octarine Services

Alex, if you have your engine out, take it to your local garage/tyre depot, and get them to undo it with a gun, if the engine is still in your car,try an loan a good battery gun, i have a Snap on 1/2" drive gun and have never failed to undo anything with that,PS make sure you use a gun socket on it if its that tight, good luck, AT
andy tilney

Thanks for your help. just to confirm, it is a standard threaded bolt (i.e. you undo it anticlockwise!) That might explain why it won't undo.

Alex Davies

Yes, standard righthand thread.

I use a right-angle bracket which I bolt into one of the starter mounting holes and it locks into the ring-gear. bottom hole for undoing, top hole for tightening. Also useful for the clutch and flywheel bolts.

It helps if you can strap the engine to something to stop it moving. Three foot bar on a socket normally works.
Dave O'Neill 2

It is a standard RH thread. Undo A/C wise.I had to use a 3 ft Stillson (pipe wrench) over a socket. Engine on stand, seized solid. Be brave, the crank will take it. The thread is only 1/2" NF but the washer face is large and that's what holds it.
Art Pearse

I strongly disagree that using a very high torque to undo the crank pulley nut, while locking the engine from turning, does not damage the engine.
The load on the wrench is directly transmitted to the front main bearing. Have a look at what it does to the soft bearing metal.
The Workshop Manual "shock" method is the only way to do it. Use a hammer or an air gun.


Mick
M F Anderson

Mick - I was rebuilding anyway. But it is better to use a very long lever as it reduces the static load on the bearing.
Art Pearse

Art,

Sorry but the physics is a bit wrong. The longer lever does not reduce the load on the bearing, it increases it. It only feels less to you because that is what levers do, they reduce the effort needed at the end of the lever.
The longer lever applies a greater force at the nut (the load), a greater force at the bearing (the fulcrum), and a lesser load at the end of the lever (the effort or force).
This is known as a First Class Lever (see diagram).

I can only state again, do not use a lever. You must believe what the engineers who designed the engine tell you. You must use a shock method to loosen the nut.
Use a hammer, an air gun, or Chris's method with the starter motor.
Just think how soft the coated bearing metal is for the front main bearing (the fulcrum).


Mick

M F Anderson

Not quite a first class lever. You are applying a torque, so the fulcrum is the center of the bolt, and the load is all around it at the bolt radius - and the washer face. The load on the bearing is solely the opposition to the force applied, but in the opposite direction.

Doesn't matter, Mick's right, use inertia/shock. I once met a guy who busted the side of the block out of something, Chev 6 I think, by blocking the crank on an unsupported section, such that his blocking acted as a wedge - POP!

I use a Craftsmen 1/2 drive ratchet that I keep for just that purpose. Once I broke it, and didn't have the gall to take it back under warranty, but a friend did and damned if Sears didn't give us a new one, despite all the very heavy hammer marks from about 20 years of such use! I since broke it again and welded the drive in place - that was another 20 years almost.

FRM
FR Millmore

Actually, the socket/hammer method also applies a force to the crank - if I am using this method on an engine out of the car, I always support the socket on a block - this also contains the axial force that tends to twist the socket off the bolt head and send it flying across the workshop.
Chris at Octarine Services

Ditto with rear hub nuts!
P Hunt

This thread was discussed between 09/01/2010 and 12/01/2010

MG MGB Technical index

This thread is from the archives. Join the live MG MGB Technical BBS now