Breaking the grip between the valve spring cap & cotters.

[philthehill]

I have just removed a couple of valves (inlet & exhaust) from a MGB cylinder head belonging to my neighbour.
He was having great difficulty breaking the grip between cotters and valve cap.
Having recently experienced the same difficulty with a 940 head I thought I would post a couple of pointers on here.
The valve spring compressor (Sykes-Pickavant) would not break the grip so I placed a small block of alloy (the thickness of the distance between valve head and bench) on the workbench and sat the head down over it so that the head of the valve to be removed sat/rested centrally on the alloy block.
I then took an appropriate sized socket & 6" extension and placed the socket/extension on the valve cap - a good thump on the end of the 6" extension with a copper lump hammer broke the grip between the cotters and valve cap. The valve spring compressor was then able to compress the spring enabling the cotters to be removed.
As the valve is restrained from moving downwards the only thing that will move is the valve spring & cap. Having the alloy block under the valve head ensures that the valve does not get damaged.
My neighbour is to use same process to remove the other 6 valves.
Phil

[bmcecosse]

A wee thump on the compressor claw with a hammer usually does the job.

[philthehill]

bmc
Tried that - but still would not budge.
Only when the valve was stopped from moving and the cap was hit did the grip between the cap and cotters become released.
Phil

[bmcecosse]

I've seen them tight - so perhaps more than a 'wee thump' required - but never failed to move them. Have the cotters perhaps dug into the caps ?? I have seen badly worn caps on a 202 head.

[bmcecosse]

I've seen them tight - so perhaps more than a 'wee thump' required - but never failed to move them. Have the cotters perhaps dug into the caps ?? I have seen badly worn caps on a 202 head.

[philthehill]

bmc
There did not appear to be any wear or digging in of the cotters into the caps on the MGB head. All seemed to be satisfactory.
The 940 head I experienced difficulty with releasing the cotters did not appear to have any problems or wear either.
Phil

[panky]

I had the same issue when stripping a Rootes 1725 alloy head. My home made valve compressor utilises a 'G' clamp and a short piece of slotted tube on the cap end ( the slot enables access to the collets) but no amount of tightening the clamp would release the grip. A sharp clout on the top of the clamp did the trick, shocking the cap from the collets, but in extreme circumstances I can see Phil's method as a better, safer option.

[philthehill]

Provided you are careful when striking the valve spring compressor all should be well but there is always the possibility that a cotter may fly out and get lost.
Ok if you have spares but not so if you lose one or more cotters. When the socket is placed on top of the cap it stops the cotter(s) from being totally displaced and possibly getting lost.
As an aside - when having fitted the valves, valve stem seals (if fitted), valve caps and cotters I always strike the top of the valve to ensure that all is correctly bedded in.
Phil