HPeacock. Re the shaking and rattling that is a characteristic of a Merlin on start. I have started Merlins many times in another life (Lincolns and Mustangs) but I had never really thought about all that vibration except it was normal. I thought it was because one or more cylinders had yet to cut in and thus it was an unbalanced crankshaft rotation causing the heavy vibration - not a variation in torque? Same thing on big radials such as the R2800 on the Convair 440.