I am interested in buying a ready machined inside cylinder block for a loco I am hoping to build. It will be some time before I actually need it but the cost and time saving is potentially great I am not one to buy things 'just in case', but this is a project for which I have been already been producing construction drawings and thus I am already fairly committed. The overall width, between frames, of the cylinder block is correct but the length is 8.4mm short of my requirements. That discrepancy may be just due to the rear cover bosses. The inside depth from the rear of the block to front cylinder cover is right and the bores are correct (or within 1/64&quot.

However, the ports (4mm x 12mm steam and 6mm x 12mm exhaust) are quite a bit different than what I want (2.4mm x 17.5mm steam and 9.5mm x 17.5mm exhaust). My concern is, as the design I am producing is based on a proven cylinder pair, is it worth trying to change the port dimensions on this ready made item. If this is the case, I wonder how successful people have been in blanking and re-boring ports; what is the best filler?

Many thanks, Dave