Can anyone confirm from these photos. I have more if needed. The wheel cylinders have A8631 stamped into them.
Also begs the question of why would you bother. The shoes friction material is 12 1/2" long which does mean more friction pad than the standard early 120.
It should also be mentioned that the system has a pbr vacuum assist installed under the right guard. This would have been installed in the seventies.
This car did have a history of racing back in the fifties and has overdrive fitted, very well done as well, no chassis hacking, seems to have a shaped chassis piece welded in and the exhaust pipe hole is gone. Original box but transmission cover is JLN22077 with the overdrive switch mounted onto a flat cast into the gear stick.
I don’t necessarily want to change it back to original as I appreciate this cars history, don’t get me wrong it wasn’t a famous car or anything, but I like its uniqueness.
Welcome to the family.
Yes, they appear to be early Mark V fixed pivot type brakes.
Here is a screen shot from the Mark V parts catalogue.
It is unlikely to be factory work, as your car dates from Nov '50, and Mark V had gone to sliding pivot type earlier than Apr '50 when my saloon was made.
Thanks Rob. I think I will get the cylinders resleeved and keep it this way. Easier in the long run.
Is that transmission cover a Mark V gearbox number as well? If so that would date the changes together as I would imagine they took all of the parts off one donor car. Poor Mark V gave its life so the XK could live on.
Mark V’s did not have overdrive. The JLN box is from a Mark VII.
There should be a number stamped on the left rear upper corner of the main case, which may tell us something.
I think you will find that the Mark V wheel cylinders are 1" diameter, where on the XK120 they are 1.125", thus your braking force on the shoes is reduced, in other words it is inferior to the original brake system.
That may be why someone thought they needed a vacuum assist. On a standard 120 braking system we don’t need it.
The number stamped on the main case is JH5151 which is the original box listed on the build plate. The engine is W2524-7 and the chassis is 660365 which all matches the plate. I am still to detect the body number but it should be F2460, any idea where I would find it?
I’ll measure the wheel cylinders when I get them out, but I take your point about the loss of force.
That’s interesting, a JH main case but converted to overdrive with JLN parts.
Not just swapping the entire gearbox as would have been the usual route.
That’s quite a bit of work; its not just a matter of bolting on the OD tail case; the main shaft would have to be changed over.
Perhaps it was a case of salvaging good parts out of two broken boxes.
May have something to do with the racing history.
