A member of Ford's FE big-block engine family, the 390 cubic-inch block is difficult to distinguished from other FE engines, as many of its components are interchangeable. The 390 is a common FE engine, first introduced in 1961 and produced through 1971 for autos and 1976 for trucks. Begin by identifying the block as an FE and then compare the casting number to a listing of known 390 numbers. If this doesn't work, measuring the bore and stroke is necessary. Casting numbers give year of manufacture and the original vehicle model, but they do not identify engine displacement.
Identify the FE block characteristics visually. According to the Fordification website, All FE engines have five valve cover bolts. Other FE engine characteristics include a skirted block, a completely flat oil pan mating surface, the number "352" cast into the rear of the block behind the flywheel and intake manifold bolts that are perpendicular to the intake face, or 45 degrees to the ground.
Locate the casting number. The casting number on all Ford FE big-blocks is found on the passenger side of the block near cylinder two, which is the third cylinder from the rear. C7AE-6051-A, for example.
Decode the Ford casting number. In the casting number prefix, C7AE, the "C" is for the decade, the 1960s; "7" is for the decade year; "A" is for a full-sized Ford passenger car; and "E" designates the engine. A full casting number decoding guide is found on the MustangTek website. For identification purposes, the prefix is the essential part of the casting number.
Reference the casting number to a listing of known 390 cubic-inch castings, similar to those found on the Fordification and What Are You Working On? websites.
Measure the bore and stroke. FordClassics.com lists the bore on the Ford 390 as 4.05 inches and the stroke as 3.78 inches. Measure the bore using a dial bore gauge and the stroke by measuring from the top of a piston at dead-bottom to the top edge of the cylinder wall.