Maximizing Torque Plate Performance
While just bolting on a torque plate is enough to put you ahead of a standard production machine shop's bore quality, paying attention to the fine points can increase the degree of accuracy substantially. Fastener loads and type, as well as the lubricants and thread engagement, torque plate stiffness and surface finish, and even gasket type can all vary the bore distortion replicated by the torque plate. It is important to mimic the final engine assembly as closely as possible. Sunnen has done extensive research in this regard, with precision bore measurements showing that these factors can materially affect the final bore quality.

True bore distortion cannot be measured with a dial bore gauge since it only measures length without considering an axis. The Inner Contour Meter is a precision device that can map the actual bore shape. This is an important tool at Sunnen in developing tooling and techniques, which closely replicate an ideal cylindrical shape. With it isometric and radial plots of the bore are generated under various conditions, allowing comparative evaluation of the cylinder bores. This is useful in solving complex distortion simulation problems, and allows compensation or correction that can lead to a better finished product.

So much attention is paid to mechanical distortion, and for good reason. However, a running engine is a dynamic system and subject to thermal loads when under operating conditions. Thermal distortion can be created by the heat of the coolant in the water jackets, taking a perfectly round and true bore out of shape. In situations demanding the ultimate in cylinder bore accuracy, a "hot-honing" process can improve the quality of the bores. Here, heated fluid is circulated through the block using a special torque plate equipped with water jackets. This system is yet another step in mimicking the engine under true operational conditions.