Some metal cylinder head gasket, you may notice that there are notches on them, so what is the meaning on that notches?
Actually the notches is the indicator on the thickness of the said cylinder head gasket, normally, if an engine head gasket is first time dismantle from the engine head, and original head gasket may don't have any notch on that gasket, and if the engine head is skim during the repairing, they might need thicker head gasket on that purpose, and the thickness may vary on how much the engine head is skim.
The above photo showing the Nissan YD25DDT engine diagram which it show the thickness with the notches count on the head gasket.
For this cylinder head gasket, it's thickness is 0.9mm and there are no notch appear on the gasket, and every added notches will add another 0.025mm thickness on it, until the thickest in the OEM specification which is 1.025mm thick with 5 notches indicator. Bear in mind that this thickness is just from the OEM specification point of view, it is not surprise that after market gasket manufacturer may developed a more thicker gasket as the demand from market, which I think 1.5mm to 2.00mm range may possible have the demand.
2 comments:
Understanding head-gasket notch markings is essential when dealing with engines that have undergone machining, because the correct gasket thickness ensures the Cylinder Head maintains proper compression and sealing after a skim. Each notch acts as a quick visual reference, letting you match the gasket to the amount of material removed from the head surface. Using the wrong thickness—either too thin or too thick—can lead to compression imbalance, sealing issues, or even long-term reliability problems. That’s why paying attention to these small details is so important, especially on engines like the YD25DDT where the specifications are precise and the notches directly reflect incremental thickness changes.
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