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I believe the reference might be 112756.

I have two brake servo's from possibly October 65, well one is most likely to be, the other I'm not sure if it is original to the car...

The one I believe is original has raised no's at the nose of the cast iron section - 051, the bore size is 5/8th. Smooth nose i.e. no score mark around the nose circumerence.

The other which appears identical in all outer visual respects, the raised numbers are 044, but the bore size is 11/16th and has a single score mark around the circumference of the nose

Would welcome thoughts on whether they are original spec or if not? and which is likely to be the correct for a 65 S,

Would also be interested to know why the difference in bore sizes and whether it has any effect on braking pressure/performance?

Thanks in advance

The 5/8 bore, one with no rings on the nose is the correct S servo.

The one with the ring will work but is not technically correct. I use one with a single ring on my Fiesta Yellow 'S' and find the brakes very good.

Information on the Lockheed servo's in on the main site, the 'nose ring' identification info is on page 9.
https://mk1-performance-conversions.co. ... _servo.pdf

Thank you Bob and Andrew!

The link to the lockhead service manual is spot on....

That’s a great source of info.

Just in the process of reassembling the brake servo after cleaning and plating, on closer examination of the secondary bore (the 5/8" one) I've noticed some disturbance to the wall surface in the area of where the rubber seal will sit.

Might fluid be passing the seal for when I stripped it apart there was quite a lot of fluid in the bellows chamber which I assume should not be there?

I guess to overcome this the bore will need resleeving?

And if so is there a company that can be recommended to do this?

Thanks in advance...

I had my servo sleeved by 'Past Parts' https://www.pastparts.co.uk/services-products/
This was about fifteen years ago and the cost was around £150 I think. They bore and fit a thin stainless steel sleeve and reseal and test the unit. It's sat in my spare room since then until I decided to strip it down to fit some re-plated vacuum and air valve chamber shells to improve the appearance. Was not impressed with the rusty air valve components and the large spring in the same state, It looks like they just fitted new seals onto the corroded parts! They only sleeve the 'working' smaller 5/8" diameter and the shorter larger diameter is left as is which was a worry as that was pitted on mine.
I rebuilt it after blasting and re-plating the rusty bits.
Might be worth giving them a call to explain exactly what you want done.

Re-sleeving reared its head some time ago too and if my memory serves me right, Spider Chris our antipodean mechanical maestro was on board to.

It's little known outside the hydraulics industry that re-sleeving cylinders is a common practice. It's also little known that the common imperial bore size cylindrical bores, highly polished and honed by the deep gun bore-drilling process are regularly used. Lengths are available off the shelf - if you know where to find them, which I don't! But they are there.

Bore out so that the liner is what technical people call '.... a stonking good fit...', insert/press in liner and that's pretty well it

On that basis alone, re-sleeving a very short bore, such as a servo, should be a simple process for a good machine shop. Alas, not one for the home amateur enthusiast with his black and decker drill.....