Picked up the cudgel on this again, I left off, where I just needed to make the motion plate and one more link arm thingy. Before I started on the motion plate tried a lose assembly just to see how things lined up in case I needed to make a small adjustment to it, and it was clear that with my new linkage there was no way things would line up, particularly with the left hand side of the loco so did a bit of measuring and

The position of the valve rod on the left hand steam chest is only out by 5mm there is no way that the linkage will miss the slide bars and the right hand one is out by 2mm.

The lines indicate where it should be.

This explains why the linkage on the loco when I bought it were all bent and cut about in short they had been well bodged.
Decided I'd better check a few more things out ports in the cylinder ok, they took a good look at the slide valve


The pocket in the face of the valve should be in the centre there is no way this would work, the narrow slot should be closer to the edge by about 3mm.
I have only two options buy new casting but I'm allergic to that word buy or rework the existing ones some way. With the steam chest I can cut the crap bits off drill and tap a hole in the correct position and screw and Loctite in some new bosses so correcting the error, with the slide valve there is no way to correct them so I've ordered some cast iron bar to make new.
So to fix the steam chest.
As nothing is square on this darn thing first thing I had to do was give myself a square face so clamped the cylinder to an angle plate fastened the steam chest to it and skimmed off its back face square, I can use this to ensure that the valves rods work parallel with the pistons.

Then using this square face clamp the steam chest onto the angle plate, line up on the scribed lines and zero the DRO

Machine the boss off and skim another face square.

Come back to the zero position and as the hole is out of position trying to drill through would cause the drill to wonder, so use a slot drill to take away the hole.

Then drill and tap 1/2"*32 ME

The surgery on the other end was not as drastic as this just had a 3/16" hole that guides the tail of the valve rod, so with this one centre on the cross lines and drill through and tap 3/8"*32 ME

Turn up and thread a couple of plugs

And screw them in good and tight with stud lock.
Remark the correct position, and set back up on the angle plate, pick up on the cross lines, drill and ream through 3/16 and drill and tap the top boss 3/8"*32 ME for the valve gland.
The front boss needs to be drilled 3/16" dead in line with the rear boss so I used a long series centre drill for this.

Need to make or buy a long series 3/16" drill to finish off, but before I got that far I got one of those Dad can you help calls from my daughter.
Stew