You'll find basically two configurations to the 4A-G cylinder block with some slight variants With all the 5 vale versions. In all scenarios they've these features in common. The cylinder block within the 4A-G is product of Forged iron alloy. There are actually 5 main bearings held with two bolts https://4age-blacktop-engine-for60210.fitnell.com/67363136/top-jdm-toyota-4a-ge-secrets