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How to Identify GT40 Cast Iron Heads

by Floyd Drake III

Considered the best factory-production small-block Ford cylinder heads, according to Reinholt Racing, Ford GT40 heads were first featured on 1993 to 1995 Cobra Mustangs. In 1996, Ford used GT40 heads on Explorers, Mountaineers and Lightnings, until the GT40s were replaced in mid-production 1997 with upgraded GT40P heads. With 1.85/1.45 intake and exhaust valves and 65 cubic-centimeter combustion chambers, the GT40 head was better suited for performance than earlier Ford cast-iron cylinder heads. Either on the engine, or off, identifying Ford GT40 heads is a simple process.

Step 1

Open the hood and look for the casting bars at the front of each cylinder head. When installed, the front of the cylinder head points forward of the vehicle. The three casting bars, or ribs, are vertical and raised from the surface of the head.

Step 2

Look on the sides of the cylinder heads. The sides of the cylinder head face towards the exhaust manifold on one side, and the intake manifold on the other. In various locations, "GT40" is cast in raised characters on each side of the cylinder head.

Step 3

Locate the Ford casting number for further identification. Ford casting numbers are part numbers cast on either the top of the cylinder head, or on the bottom, which requires removing the cylinder head. First, remove the valve cover from the top of the cylinder head using a 3/8-drive ratchet and the appropriate socket. The casting number, if located on top, is in the center of the GT40 head.

Decode the Ford casting number. The casting number identifies the year and original vehicle type. On Ford cylinder heads, the casting number is normally abbreviated with the prefix. The prefix, "F4ZE" identifies a 1994 head, with "F" representing the 1990s, and "4," for '94. Mustangs are identified by "Z," and "E" means the part is an engine component. For a full listing of Ford casting number codes, refer to sites such as Mustang Tech and FoMoCo.org.

Tip

  • If the casting number is not on top of the cylinder head, and the head is still installed on the engine, it needs to be removed in order to view the casting number. Unless mechanically inclined, it is not suggested as other key parts need to be removed first, and the head torqued to specific settings. The process can be difficult.

Items you will need

  • 3/8-inch ratchet
  • 3/8-drive socket set
  • Ford casting number reference listing

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