Mitsubishi 4D56 Cylinder Heads – Understanding the Four Different Types and How to Choose the Correct One
Not All 4D56 Cylinder Heads Are the Same!
The Mitsubishi 4D56 2.5L diesel engine is one of the most widely used diesel engines found in Mitsubishi Delica L300, Pajero, Montero, L200, and other vehicles.
Although these engines share the same basic 4D56 engine designation, there are four commonly used cylinder-head configurations, and they are not necessarily interchangeable.
Choosing the wrong cylinder head can create problems with valve clearance, combustion chamber geometry, engine performance, and installation compatibility.
At HiYota Parts, we want to make sure customers receive the correct cylinder head for their specific engine.
This guide explains the four different 4D56 cylinder heads, their measurements, and how to identify which version you need.
The Four Different Mitsubishi 4D56 Cylinder Heads
The four common cylinder-head reference numbers are:
- 908511 – Recessed Valve Configuration
- 908512 – Protruding Valve Configuration
- 908513 – Recessed Valves with Oval Pre-Combustion Chamber
- 908770 – Larger Valve Configuration
These cylinder heads have different valve-seat dimensions, valve positions, and pre-combustion chamber designs.
Cylinder Head Measurement Comparison
|
Specification |
908511 |
908512 |
908513 |
908770 |
|---|---|---|---|---|
|
Valve-seat measurement A |
3.2 mm |
0.8 mm |
3.2 mm |
0.8 mm |
|
Intake seat outer diameter (D) |
43 mm |
43 mm |
43 mm |
45 mm |
|
Intake seat inner diameter (d) |
36 mm |
36 mm |
36 mm |
38 mm |
|
Exhaust seat outer diameter (B) |
37 mm |
37 mm |
37 mm |
38 mm |
|
Exhaust seat inner diameter (b) |
30 mm |
30 mm |
30 mm |
31.8 mm |
|
Pre-combustion chamber exit |
Rectangle |
Rectangle |
Oval |
Rectangle |
|
Intake valve diameter |
40 mm |
40 mm |
40 mm |
42 mm |
|
Exhaust valve diameter |
34 mm |
34 mm |
34 mm |
36 mm |
|
Valve length |
130 mm |
132 mm |
130 mm |
136 mm |
|
Valve position |
Recessed |
Protruding |
Recessed |
Protruding |
Important: These measurements are based on the cylinder-head comparison chart and should be confirmed against the specific cylinder-head manufacturer’s specifications before ordering.
1. Mitsubishi 4D56 Cylinder Head – 908511
Recessed Valve Configuration
The 908511 cylinder head uses a rectangular pre-combustion chamber opening and recessed valves.
Key Specifications:
- Intake valve diameter: 40 mm
- Exhaust valve diameter: 34 mm
- Intake valve-seat outer diameter: 43 mm
- Exhaust valve-seat outer diameter: 37 mm
- Valve length: 130 mm
- Valve-seat measurement: 3.2 mm
- Pre-combustion chamber: Rectangle
- Valve position: Below the cylinder-head surface
This configuration is commonly associated with earlier 4D56 engine applications.
The recessed valve design is an important identifying feature.
Do not assume that a cylinder head with protruding valves can directly replace this version.
2. Mitsubishi 4D56 Cylinder Head – 908512
Protruding Valve Configuration
The 908512 cylinder head looks very similar to the 908511, but there is an important difference.
The valves sit above the cylinder-head surface rather than being recessed below it.
Key Specifications:
- Intake valve diameter: 40 mm
- Exhaust valve diameter: 34 mm
- Intake valve-seat outer diameter: 43 mm
- Exhaust valve-seat outer diameter: 37 mm
- Valve length: 132 mm
- Valve-seat measurement: 0.8 mm
- Pre-combustion chamber: Rectangle
- Valve position: Above the cylinder-head surface
Although the valve diameters are the same as the 908511, the valve length and valve position differ.
This distinction is particularly important when replacing a damaged or cracked cylinder head.
Always verify the valve position before selecting a replacement.
3. Mitsubishi 4D56 Cylinder Head – 908513
Oval Pre-Combustion Chamber Configuration
The 908513 cylinder head is easily identified by its oval-shaped pre-combustion chamber opening.
Unlike the 908511 and 908512, which use rectangular openings, this version has a distinctly different chamber design.
Key Specifications:
- Intake valve diameter: 40 mm
- Exhaust valve diameter: 34 mm
- Intake valve-seat outer diameter: 43 mm
- Exhaust valve-seat outer diameter: 37 mm
- Valve length: 130 mm
- Valve-seat measurement: 3.2 mm
- Pre-combustion chamber: Oval
- Valve position: Below the cylinder-head surface
This configuration is commonly associated with certain later 4D56 applications.
The pre-combustion chamber shape is one of the easiest ways to identify this cylinder head.
If your original cylinder head has an oval chamber opening, verify that the replacement has the same configuration.
4. Mitsubishi 4D56 Cylinder Head – 908770
Larger Intake and Exhaust Valve Configuration
The 908770 cylinder head differs significantly from the other three versions.
This configuration uses larger intake and exhaust valves.
Key Specifications:
- Intake valve diameter: 42 mm
- Exhaust valve diameter: 36 mm
- Intake valve-seat outer diameter: 45 mm
- Intake valve-seat inner diameter: 38 mm
- Exhaust valve-seat outer diameter: 38 mm
- Exhaust valve-seat inner diameter: 31.8 mm
- Valve length: 136 mm
- Valve-seat measurement: 0.8 mm
- Pre-combustion chamber: Rectangle
- Valve position: Above the cylinder-head surface
The larger valve diameters make this version relatively easy to distinguish once measurements are taken.
Do not select this cylinder head simply because your engine is a 4D56.
The valve sizes and other specifications must match your original engine configuration.
How to Identify Which 4D56 Cylinder Head You Need
If you are replacing a cracked, damaged, or worn Mitsubishi 4D56 cylinder head, there are several measurements you should check.
Step 1: Identify the Pre-Combustion Chamber Shape
Turn the cylinder head over and inspect the combustion face.
Look at the small pre-combustion chamber openings.
There are two common shapes:
Rectangle: Found on cylinder-head configurations 908511, 908512, and 908770.
Oval: Found on cylinder-head configuration 908513.
This is an excellent starting point for identifying your cylinder head.
Step 2: Measure the Intake and Exhaust Valves
Measure the diameter of the valve heads.
There are two common valve-size combinations in these four configurations:
Standard Valve Configuration:
- Intake: 40 mm
- Exhaust: 34 mm
Larger Valve Configuration:
- Intake: 42 mm
- Exhaust: 36 mm
If your cylinder head has 42 mm intake valves and 36 mm exhaust valves, it may be the 908770 configuration.
Step 3: Check Whether the Valves Are Recessed or Protruding
This is one of the most important differences.
Some 4D56 cylinder heads have valves that sit below the cylinder-head surface.
Others have valves that protrude above the surface.
The valve position must be checked carefully because it affects engine geometry and piston-to-valve clearance.
Never assume that two cylinder heads are interchangeable simply because they have the same valve diameter.
Step 4: Measure the Valve Seats
The intake and exhaust valve seats have different dimensions depending on the cylinder-head configuration.
For example:
908511, 908512, and 908513:
- Intake seat outer diameter: 43 mm
- Exhaust seat outer diameter: 37 mm
908770:
- Intake seat outer diameter: 45 mm
- Exhaust seat outer diameter: 38 mm
These measurements can help distinguish the larger-valve version from the other configurations.
Step 5: Verify the OEM Part Number
Whenever possible, identify the original Mitsubishi or Hyundai OEM cylinder-head part number.
OEM references can help determine which replacement cylinder head is appropriate for your engine.
Keep in mind that replacement engines and previously rebuilt engines may not have their original cylinder heads.
For this reason, physical measurements are often more reliable than relying on the vehicle model or year alone.
What Happens If You Install the Wrong 4D56 Cylinder Head?
Installing an incorrectly matched cylinder head can potentially cause several problems:
- Incorrect valve-to-piston clearance
- Changes in combustion chamber geometry
- Poor engine performance
- Starting difficulties
- Incorrect valve-train geometry
- Installation or compatibility problems
- Potential internal engine damage
Even if two cylinder heads appear identical externally, their internal specifications may differ.
This is why we recommend checking the original cylinder head before purchasing a replacement.
Need Help Choosing the Correct 4D56 Cylinder Head?
At HiYota Parts, we specialize in Mitsubishi Delica L300 and other Japanese diesel vehicles.
We understand how frustrating it can be to order a replacement cylinder head only to discover that it is the wrong configuration.
If you are unsure which Mitsubishi 4D56 cylinder head your engine requires, contact us before ordering.
To help identify the correct replacement, please provide:
- Your vehicle’s year, make, and model
- Engine code
- VIN or chassis number
- Photos of the original cylinder head
- Photos showing the pre-combustion chamber openings
- Intake and exhaust valve measurements, if available
- Any visible OEM or casting numbers
Our goal is simple: Help you get the correct cylinder head the first time.
Whether you’re rebuilding a Mitsubishi Delica L300, Pajero, Montero, or another vehicle equipped with the 4D56 diesel engine, HiYota Parts is here to help you find the right replacement components.
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