YD25 Early and Late Cylinder Head Differences
The Nissan YD25 engine has two variances in the cylinder heads. The original YD25 engine was introduced in 2002 in the Navara. A few years later, it was used in the Pathfinder (2005). This is generally referred to as the Early YD25 cylinder head - if you have the manifold off, it is easily identified by the four inlet ports. In 2010, Nissan released a different YD25 head - again, if you have the manifold off, the easily identifiable feature being the eight inlet ports - there is also a 5XO cast onto the head. This eight-port head is referred to as the Late YD25 Head or a YD25 5XO.
If your engine is still complete, you can still identify the early and late head. This is done by locating the glow plugs. On the early YD25 head, the glow plugs are on the exhaust side (this is the passenger side in Australia, being a right-hand drive car). The late YD25 head (or 5XO) has its glow plugs on the inlet side of the head (this is the driver’s side in Australia, being a right-hand drive car).
Nissan did not stop using the early head with the introduction of the late (eight-port) head. To avoid ordering the wrong head for your vehicle, it is best to have a quick look at the original head you are replacing. This will save time and freight costs for you.
We have a video on our YouTube channel talking about these two heads. Link: https://youtu.be/jCDtZr7MzyM