When an engine manufacturer offers both a .40 and .46 engine, many components between the 2 sizes are the same. A .46 will typically use the same stroke as the .40 - hence the crankshafts are the same. The crankcase casting and backplate would also be identical. The larger .46 gets it's increased displacement via a larger bore size. Usually (almost always) this is achieved by using a thinner liner than the .40 engine. The piston, liner and cylinder heads (and wrist pin) are usually the only difference. In an ABC engine, the liner is brass which has been chrome plated. Other manufactures use nickel instead of chrome. Since brass is relatively heavy, the larger .46 engine will be slightly more powerful than a .46 from the same manufacturer.

The OS LA .40 and .46 are excellent examples of this commonality.

For those of us who fly control line aerobatics, the slight change in displacement is significant. The C/L rules specify a minimum line diameter of .015" for engines up to .40 cubic inches. A .46 or larger engine must use .018" lines. The difference in weight and thickness (drag) of the larger lines is very noticeable.