The D during the engine code stands for dual overhead camshaft (DOHC). This is achieved by fitting an RB25DE or RB26DETT cylinder head and or turbo to a normal RB30E/T block. The RB25DET just isn't commonly used.The RB25 crank collar difficulty is actually very common on many RB motors, including the RB20DET and pre-1993 RB26DETT. The challenge Whi… Read More