Apart from being the loudest SOB on the block, I think it was one of the most engineered engines ever built . What other engine can you build from a pile of parts 8 different ways . reverse rotation , switch the block front to back , put cam on each side , switch head front to back , etc etc . The 71 series i think came out in 1938 for the military tanks and everything was basically the same right up into the 80s or there abouts. After running DDs for the last 40 years and now half deaf LOL , I have nothing bad to say about the 71 series DD other than the noise and the oil leaks . Now as for the 53 series ( unless its in a compressor or something with a constant speed) , I'll call it a poor mans engine ............you'll always be poor while you own it LOL . The 92 series is worse !!!