Hi I have decided to remove the cylinders and steam chest from the frames as i cannot get the timing right, i intend to drill sighting holes to view the valves and get them in the right position, so as it all apart is it worth changing to cast iron piston rings or staying with the o rings?Also as it is an early winson it does not have drain cocks, are they really worth fitting? Any other mods or advise would be very gratefully received. Dave
if the cylinders are cast iron then cast iron pistons with cast iron rings are to be preferred to 'O' rings. rub an ordinary eraser along the bores to see what happens! unless the bores are dead smooth (that's really smooth!) 'O' rings will wear. however changing over to new cast iron pistons and fitting cast iron rings is quite a precision job.
there are other ways to set the valves. sighting holes might prove pretty awkward and not provide the accuracy you seek when you come to valve setting.
i am sure others can help with their experience of your design of loco, and hints and tips to avoid the major job you are thinking of.
Hi Julian thanks for a quick reply, the cylinders are cast iron and the bores are smooth but not what i would say as silky, i can see machining marks so they have not been lapped, i suspect you are right about the o rings wearing quickly. luckily for me there is very talented model engineer locally who prefers to build rather than run engines so i shall see if i can persuade him to help. regards Dave