How do you identify a Ford GT40 head?

In short, there isn’t a single Ford GT40 head to look for—the GT40 program used two main engine families across its variants: Windsor-based small-blocks for the early Mk I cars and FE big-blocks for the Mk II racers. You identify a GT40 head by checking factory casting numbers, distinctive design features, and the car’s documented provenance. This article explains how to tell which head you’re dealing with, what to measure, and where to find authoritative references.

Two eras, two families: what to know

Mk I Windsor-based engines

The GT40 Mk I relied on Ford Windsor-based V8s, typically in the 289/302 displacement range. Identification centers on Windsor-style head castings, with characteristics familiar to enthusiasts of early Ford small-blocks. Reading the casting numbers and comparing port shapes with Windsor references helps confirm this origin.

Mk II FE-based engines

The GT40 Mk II shifted to a large-displacement 427 cubic-inch FE engine. Cylinder heads for this era are FE-type heads, which feature larger ports and a different combustion chamber geometry than Windsor heads. Look for matching FE-era casting identifiers and features that align with the FE family and the Mk II’s racing configuration.

These distinctions matter because the correct head type informs everything from restoration accuracy to value. The next steps focus on the official identifiers and reliable references you should consult to verify your head’s origin.

Casting numbers and dates

Casting numbers and date codes are the most reliable way to identify a GT40 head. Use these steps to focus your search.

• Casting numbers: Locate the stamped or raised casting marks on a flat area of the head (often near the exhaust port or on the rocker area). Cross-reference the sequence with Ford’s casting catalogs or GT40 registries to determine whether the head belongs to Windsor (Mk I) or FE (Mk II).


• Date codes and family markers: Casting codes typically include a year indication and a family identifier. Use authoritative reference lists to narrow the head to the correct era and engine family for GT40 usage.


• Readability and documentation: If markings are faint, carefully clean the area and photograph from multiple angles to capture legibility for remote verification.

The numbered identifiers and corroborating details from catalogs or registries offer the most dependable confirmation that a head is authentic to a GT40 build.

Visual cues to distinguish at a glance

Beyond numbers, certain design cues help you assess a head’s likely GT40 lineage when documentation is limited.

• Port size and geometry: FE heads generally show larger intake and exhaust ports suitable for the big-displacement engine, while Windsor heads have the smaller, traditional small-block port geometry.


• Combustion chamber shape: Windsor and FE heads differ in chamber design, which affects compression and combustion characteristics and can be a telltale clue when seen alongside a casting number.


• Physical scale and mounting features: FE heads are heavier and built to accompany the larger FE block and its mounting patterns; Windsor heads are lighter and aligned with the Windsor-family mounting specifics used on earlier GT40 configurations.

Because appearance can be altered by rebuilds or aftermarket parts, rely on casting numbers and provenance in parallel with any visual assessment for a reliable identification.

Provenance and documentation

Documentation plays a pivotal role in authentication, especially for high-value GT40 components. Follow these steps to verify provenance.

1. Review original build sheets and race history tied to the chassis or engine option. The GT40 program preserved detailed records that link specific heads to particular cars and race configurations.


2. Match casting numbers and any serial markings to known GT40 engine builds. Cross-check against Ford archival catalogs and established GT40 registries maintained by museums and enthusiast groups.


3. Consult experienced restorers or GT40 specialists who can assess the head in the context of the car’s VIN, chassis history, and any accompanying paperwork.

Even with matching numbers, independent verification with authoritative sources reduces the risk of misidentification, enhances authenticity, and supports accurate restoration work.

Summary

To identify a Ford GT40 head, start by establishing whether the head originates from the Mk I Windsor-based engine family or the Mk II FE-based engine family, using casting numbers and date codes as the primary evidence. Supplement this with visual cues like port size and chamber shape, and always corroborate with provenance, build sheets, and reputable GT40 registries. When in doubt, consult a restoration expert or museum archive to confirm authenticity and engine-family alignment. Proper identification ensures restoration accuracy and preserves the GT40’s racing heritage.

How to tell if a ford GT is real?

7 external clues:

1. GT gas cap.
2. GT trumpet exhaust.
3. GT stripes.
4. MUSTANG lettering.
5. GT Badge.
6. Disc brakes.
7. GT fog light bar.

Why are they called GT40 heads?

Understanding Gt40 Cylinder Heads
The name GT40 is a nod to Ford's legendary GT40 sports car, which dominated the 24 Hours of Le Mans in the 1960s. The GT40 Cylinder Heads were designed to bring some of that racing pedigree to the street.

How do I identify my ford cylinder head?

Ford cylinder heads can be identified by checking casting numbers, which are usually stamped on the side or bottom of the head, and by visual cues like port shape or valve size. The casting number is the most reliable method, as it provides the year and vehicle it was designed for, while visual details like port shape can help differentiate between variations, such as performance (PI) and non-performance improved (non-PI) heads. 
This video shows how to locate casting numbers on Ford cylinder heads: 51sWiseAutoToolsYouTube · May 17, 2016
Using casting numbers

• Decode the number: Ford cylinder head casting numbers generally follow a format: a letter for the decade, a numeral for the year, a letter for the vehicle line, and a letter for the engineering division (most often "E" for engine). 
• Locate the number: Look for the casting number stamped on the side of the head, often above the exhaust manifold, or on the underside in the intake valley. 
• Consider the date code: A separate date code stamped on the head can indicate the specific casting date, which is helpful for very early models or when a head was manufactured in late 1970 for a 1971 model year vehicle. 

Using visual cues

• Intake port shape: On modular 4.6L, 5.4L, and 6.8L engines, compare the intake ports. Non-PI heads from 1992-1999 have tear-drop shaped ports, while PI heads from 2000 onward have rectangular ports. 
• Valve and chamber size: For older engines like the 221/260, the combustion chamber size and valve sizes are key identifiers. For example, the 260 head is distinguished from the 221 head by its larger chamber size, and a specific C4OE-B head has even larger valves. 
• Four-barrel/closed chamber markings: On 351C heads, a "4" in the front corners typically indicates a four-barrel head, and a dot often signifies a closed chamber, though this can vary. 
• Specific engine features: Some models have unique identification features. For example, "GT40P" heads have "GT40P" stamped in the lifter valley and are found in mid- to late-90s Explorers. 

This video explains how to identify cylinder heads on Ford Modular engines: 56sAutorestomod Manic Mechanic Gasoline MediaYouTube · Mar 8, 2022

How do I know if I have GT40 heads?

How to identify your GT40 heads look for a "GT" or "GT40P" stamp inside the head casting or a three-bar (GT40) or 4 bar (GT40P) stamped on the side of the head. GT40 heads can be found pretty much anywhere you look.