Which tool is best for checking the flatness of a cylinder head?

The best tool for checking the flatness of a cylinder head is a straight edge. This tool provides a reliable way to assess the alignment and uniformity of the cylinder head's surface by placing it across the head and checking for gaps. Any deviation from a flat surface can indicate warpage, which can affect the engine's performance and sealing with the engine block or gasket.

Using a straight edge allows the technician to visually and physically inspect the surface and compare it to a known flat reference. When a straight edge is used in conjunction with a feeler gauge, it provides a clear indication of any high or low spots on the cylinder head surface.

Dial gauges, depth micrometers, and calipers serve different functions in mechanical measurements and are not designed specifically for checking flatness. While a dial gauge can measure small variations in height and a caliper can measure thickness across surfaces, it is the straight edge that is specifically suited for this direct type of flatness inspection.