The real problem with that kind of cylinder is the honing after plating. In a traditional cylinder, the honing tools can travel through both the top and the bottom of the bore with no obstruction. We call that a “through bore”.
But let’s consider a cylinder with an integrated crankcase.
In that kind of cylinder, the honing tools can’t travel through the whole length of the bore because the crankshaft journals are in the way. That is called a “blind bore”.
Honing a blind bore with a relatively soft surface like cast iron is fairly straightforward because our diamond honing tools are much harder than the surface that is being cut.
The difficulty comes when we try to hone our very hard nickel/silicon carbide metal/ceramic composite coating, since the silicon carbide particles are almost as hard as the diamonds themselves, and are far harder than the matrix that binds the diamonds together in out honing tools.
The effect is that the parts of the diamond tools that are constantly in contact with the bore surface (because they can’t pass through into open air) start to wear slightly compared to the rest of the tools, and so the diameter of one end of the tool becomes smaller than at the other end.
When that starts to happen, and it will, there is nothing that can be done to avoid creating a tapered bore which is smaller near the crankcase than at the end of the bore where the head attaches.
Honing just one bore may not wear the diamond tools more than just a few microns, but subsequent bores will exaggerate the taper.
The same principle applies to cylinders with an integrated head.
Honing equipment manufacturers have developed a variety of ways to combat this problem, and engine manufacturers who are making the same size of blind bore on a mass production basis can design tools or procedures to practically overcome the issue altogether.
Our business is a little different though, since we deal with an enormous range of bore lengths, diameters and configurations every day.
Since 1984, we have taken pride in making bores extremely straight and extremely round, and we aren’t willing to supply bores that we know aren’t the very best that they can be, so, until we and our tool suppliers can develop a good, reliable solution to the problem, we will choose not to process “blind bores” at our UK facility, except for engine manufacturers where the costs of special machines and tools can be justified.