2004-2010 Cylinder Head (One) Cast Iron - 6.6L Duramax 2004.5-2010 LLY/LBZ/LMM Ported (110100113)Description The OEM Duramax cast aluminum cylinder heads fall short over time the different heat expansion rates between cast iron engine block and cast aluminum cylinder head cause head gasket scrubbing, and eventually blown head gaskets. The aluminum cylinder heads are also prone to warping, melting, and or cracking in high performance applications where excessive heat is introduced. PPEs new ported Cast Iron Cylinder Head is the ultimate upgrade to