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Does anyone know how to identify the correct Lockheed 51/2 servo for a cooper s from all the 51/2 servos fitted to other cars ?

Do you have to strip them out and measure the bore ?

I'm told they have identifying marks machined on the casting

Mine has a circular groove near the end which signifies a piston size the same as the mk3 (?)

When you know what you are looking for it all makes sense - unfortunately I cant tell you any more than that.

I,ve seen them with no groove , one groove and 3 grooves .

Hi Simon, just rebuilt 2 on sat , i have six in total, 5 have no rings on nose, small bore but the air valve actuating piston has two sizes of bore both parts in kit from Powertrack brakes some times if you are lucky the main bore is sleeved in stainless 3 of my 5 are this , this brings us to the sixth , nose has 3 rings and has large bore ,not S, I have used this for parts . I have rebuilt them all myself, most important fitting a new stainless piston rod as original chrome rusts then rips seal. What have you got there ? Peter

I.ve looking for one in the shed for somebody , most of mine have no rings or 1 ring .

Two of the no ring ones have tags on them with lockheed part numbers one matches cooper s but the other is listed rover / vauxhall ??

I also have two with 3 rings on them

I've got three here :-
the one off my 1071 has no ring and is 5/8" x 3/4" bore
the other two I've picked up at shows and have one ring 11/16" x 1" bore
I did speak to JL spares a while ago and they said it was possible to sleeve both bores to the smaller size.

Thanks for that Bob

Perhaps someone can tell us what the 'three ring' servo piston diameters are, before I buy any more duds

So the "one ring" version with different bore size, was it ever fitted to any Mk1 S as standard?