What is the acceptable cylinder head warpage?

Cylinder head warpage is a common issue in automotive engines, and it's crucial to understand the acceptable limits to ensure proper engine performance and longevity. In this article, we'll explore the concept of cylinder head warpage, its causes, and the acceptable tolerances that should be maintained.

What is Cylinder Head Warpage?

Cylinder head warpage refers to the distortion or bending of the cylinder head surface, which can occur due to various factors, such as thermal stress, uneven tightening of the head bolts, or manufacturing defects. This warpage can affect the sealing between the cylinder head and the engine block, leading to issues like oil or coolant leaks, uneven combustion, and reduced engine efficiency.

Causes of Cylinder Head Warpage

• Thermal Stress: Repeated heating and cooling cycles during engine operation can cause the cylinder head to expand and contract, leading to warpage over time.


• Uneven Tightening of Head Bolts: If the cylinder head bolts are not tightened evenly or to the correct torque specifications, it can result in uneven stress distribution and cause the head to warp.


• Manufacturing Defects: Improperly cast or machined cylinder heads can have inherent warpage, which may worsen over time due to the stresses of engine operation.

Cylinder head warpage is a critical issue that should be addressed promptly to maintain engine performance and prevent further damage.

Acceptable Cylinder Head Warpage Limits

The acceptable cylinder head warpage limits vary depending on the engine design and manufacturer specifications. However, as a general guideline, the maximum allowable warpage is typically between 0.003 inches (0.076 mm) and 0.005 inches (0.127 mm) across the entire surface of the cylinder head.

Exceeding these limits can lead to various issues, such as:

• Uneven sealing between the cylinder head and engine block, causing oil or coolant leaks


• Improper combustion due to uneven cylinder head-to-block mating surface


• Increased risk of engine failure or reduced engine lifespan

It's important to note that the acceptable warpage limits may vary depending on the engine design, materials used, and the specific manufacturer's recommendations. Always refer to the manufacturer's specifications when checking for cylinder head warpage.

Measuring and Checking Cylinder Head Warpage

To measure cylinder head warpage, a dial indicator or a straightedge and feeler gauges are commonly used. The cylinder head should be checked in multiple locations, including the center and the corners, to ensure that the warpage is within the acceptable limits.

If the cylinder head warpage exceeds the acceptable limits, it may require resurfacing or replacement to restore the proper sealing and engine performance.

What is the maximum cylinder head distortion?

Most aluminum heads using a multi-layer steel (MLS) head gasket should have no more than 0.002-inch (0.05 mm) of total distortion (block plus head combined) in any direction.

What is the tolerance for a cylinder head?

Modern engine with steel head gasket would require a maximum of 0.003" or 0.075mm. You can have a more irregular surface if you have an older engine with thicker compressible head gasket.

How flat does a cylinder head need to be?

A cylinder head's flatness tolerance is generally 0.0020.0020.002 to 0.0040.0040.004 inches or 0.050.050.05 to 0.100.100.10 mm, but the exact specification depends on the engine. A common rule is 0.0010.0010.001 inch of tolerance per cylinder, with slightly more allowable for longer inline six-cylinder heads. If a feeler gauge can fit between a straight edge and the cylinder head's surface, it indicates the head is warped and should be resurfaced. 
This video demonstrates how to check the flatness of a cylinder head: 59sCrown Racing Co.YouTube · Mar 10, 2022
General flatness specifications

• 0.0020.0020.002 to 0.0040.0040.004 inches (0.050.050.05 to 0.100.100.10 mm): This is the most common range for most 4, 6, and 8-cylinder engines, according to resources like Engine Pro and Quora users. 
• 0.0010.0010.001 inch per cylinder: A popular rule of thumb is that a head should not be out-of-flat by more than 0.0010.0010.001 inch for every cylinder it has. For example, a 4-cylinder head should not be more than 0.0040.0040.004 inches out-of-flat. 
• Inline 6-cylinder engines: These may have a slightly higher tolerance, sometimes up to 0.0060.0060.006 inches. 
• Sideways flatness: The head should be even flatter when checked for warpage from side to side, with a maximum of 0.0010.0010.001 to 0.0020.0020.002 inches. 

How to check for flatness

1. Get the right tools: You will need a machinist's straight edge and a set of feeler gauges. 
2. Place the straight edge: Lay the straight edge across the cylinder head in various locations—lengthwise, diagonally, and across the width. 
3. Check for gaps: Try to slide a feeler gauge between the straight edge and the cylinder head. 
4. Determine if it needs resurfacing: If you can easily slide a feeler gauge with a thickness exceeding the manufacturer's specification under the straight edge, the head is warped and will need to be resurfaced by a machine shop. 

This video explains how to check the flatness of a cylinder block: 53sTransportation Heavy Equipment TechYouTube · Jun 1, 2021

How much cylinder head warpage is acceptable?

The cylinder head warpage limit varies by manufacturer, but common limits are around 0.0020.0020.002 to 0.0040.0040.004 inches (0.050.050.05 to 0.100.100.10 mm). Some engines may allow slightly more, such as 0.0060.0060.006 inches (0.1520.1520.152 mm) for a straight-six engine. To measure, a precision straightedge and feeler gauge are used across the head's surface in multiple directions. If the warpage exceeds the manufacturer's specification, the head typically needs to be machined or replaced.
 
This video explains the causes of cylinder head warpage: 59sThe AbJ GarageYouTube · Oct 11, 2025
Common warpage limits

• 0.0020.0020.002 inches (0.050.050.05 mm): A common limit, particularly for modern aluminum heads with Multi-Layer Steel (MLS) gaskets. 
• 0.00320.00320.0032 inches (0.080.080.08 mm): A specific example for a Toyota engine. 
• 0.0040.0040.004 inches (0.100.100.10 mm): A common maximum allowable limit for some engines. 
• 0.0060.0060.006 inches (0.1520.1520.152 mm): The limit for a straight-six engine according to one source. 

This video demonstrates how to check for cylinder head warpage: 58sFel-Pro GasketsYouTube · Nov 4, 2021
What to do if the limit is exceeded

• Machining/Resurfacing: If the warpage is within the limit, a machine shop can resurface the head to make it flat again. 
• Replacement: If the warpage is beyond the service limit, the cylinder head must be replaced.