How To Identify Gt40 Heads

How to Identify GT40 Heads: A Comprehensive Guide

Identifying genuine GT40 cylinder heads can be tricky, as many replicas and aftermarket parts exist. This guide will walk you through the key features to help you distinguish authentic GT40 heads from imitations. Knowing how to identify these heads is crucial whether you're building a high-performance engine or simply verifying the authenticity of parts you're considering purchasing.

Key Features of Genuine GT40 Heads

Genuine Ford GT40 cylinder heads possess several distinguishing characteristics that set them apart from their counterparts. Pay close attention to these details:

1. Casting Numbers: The Most Reliable Identifier

The casting number is the single most reliable way to identify genuine GT40 heads. Look for these numbers, typically cast into the head itself:

• Ford GT40P heads: These will have a casting number that typically starts with "F" followed by a series of numbers. The exact numbers can vary depending on the specific revision.
• Ford GT40X heads: These are a slightly different version and will have a casting number that starts with a different letter or number.

Important Note: Counterfeiters often try to replicate these numbers, but careful examination can reveal inconsistencies. Look for deep, sharp castings rather than shallow, poorly defined numbers.

2. Intake and Exhaust Port Geometry

The intake and exhaust port geometry of genuine GT40 heads is highly specific and contributes significantly to their performance characteristics. Replicas often fail to accurately replicate these intricate details. Look for:

• Smooth, consistent port surfaces: Genuine heads exhibit a high level of finish and consistency in their porting. Rough edges or inconsistencies may indicate a replica.
• Precise port dimensions: While precise measurements require specialized tools, visual inspection can often reveal discrepancies in port size and shape compared to known specifications.

3. Valve Guide and Spring Sizes

The valve guide and spring sizes are critical components that affect engine performance and longevity. Genuine GT40 heads utilize specific valve guides and springs designed for high-performance applications.

• Measure the valve stem diameter: If you have access to calipers, measure the diameter of the valve stems. This can help you verify whether the valve guides are appropriate for the heads.
• Inspect spring dimensions: Compare the spring dimensions to known specifications for GT40 heads. Any discrepancies could indicate a counterfeit part.

4. Overall Quality and Finish

The overall quality and finish of genuine GT40 heads are superior to those of replicas. Look for:

• Clean casting: Genuine heads have a smooth, consistent surface finish with minimal imperfections.
• Consistent surface texture: The surface texture should be uniform across the entire head.
• Proper machining: All surfaces should be machined precisely. Any evidence of sloppy machining indicates a replica.

Where to Find Information and Further Verification

If you're still unsure about the authenticity of a set of GT40 heads, consider consulting with experienced engine builders or Ford specialists. They often have the expertise to identify subtle differences that can easily be missed by the untrained eye. Online forums dedicated to Ford engine building can also be a valuable resource for comparing your heads to known examples.

Conclusion

Identifying genuine GT40 cylinder heads requires a careful and thorough inspection. By paying close attention to the casting numbers, port geometry, valve guide and spring sizes, and overall quality, you can significantly improve your chances of avoiding counterfeit parts and ensuring you're using the best components for your performance engine build. Remember, using genuine parts is crucial for optimal performance and engine longevity.