Build, text and photos by Mike Mavrigian
Using all new GM plugs, I installed the four threaded water jacket and oil plugs on the outside of the block (three steel 16mm plugs and one brass 30mm plug). These plugs feature straight metric threads. No NPT threads exist on the OE block. The new GM threaded plugs feature thread sealant already applied. If re-using old threaded plugs, be sure to apply Teflon thread sealant. DO NOT install these plugs without thread sealant.
The front oil galley hole (facing the front of the block, this hole is located to the right of the main bore; driver-side) was plugged with a new 16mm-diameter GM P/N 9427693 expansion plug, with a film of RTV applied to the plug perimeter and driven into the block flush with the front block timing cover gasket surface.