Oh I didn't mean to cast negative aspersions on Stuart in particular - just castings in general. A poor choice of thread title...although as it happens I had problems with a 10V casting and some of the castings for the twin launch i'm working on look like the two halves were flung together in an awful hurry. I'll send them a message and see if they respond (and I will be most appreciative if they do).
Mark, as it has already been said the best of foundries can have a hard piece or a blow hole.
I have built many Stuart engines from castings bought from Stuart in the Channel Island and had some minute problems that were immediately replaced on contact with them and in general have found thier castings very good.
However having completed a set of Launch engine castings I must say that they were the poorest that I have ever had to machine and as they were bought on e-bay I just had to get on with it.
The eccentric casting like yours had a very hard bit in it but after machining although it left a little bit of a pit ran very true.
The Major problem was with the cylinder casting, that after machining and cleaning out the exhaust and steam ports on final assembly the engine just wouldn't run,
On further checking I discovered that the ports were not cast as per the drawing so I had to make a plate from 1/16" thk gauge plate and mill the ports to the correct dimensions as shown on the drawing and fit them between the cylinder casting and the steam chest, so double check the ports on the casting to the drawing.
Her are some pics of the eccentric casting and if you look close to the finished engine you can just see the gauge plate and a DRG of the dimensions of the ports cast in the cylinder and the dimensions in black are what they should be.
George.