The D within the engine code stands for twin overhead camshaft (DOHC). This is often achieved by fitting an RB25DE or RB26DETT cylinder head and or turbo to a normal RB30E/T block. The RB25DET is not really normally used.While this isn’t much an engine flaw about This is a design flaw, it does have an impact on the RB30ET inside the Holden VL Com