My guess as to why they used pal nuts on dipper engines, but stopped using them on engines with insert connecting rod bearing was due to the possibility to run the engine with babbitt bearings longer before you ran out of bearing material. Seems to me that a well worn, loose babbitt connecting rod is more likely to rattle a connecting rod nut loose if it weren't held fast by a pal nut. Add to the scenario the extra stress on everything caused by a loose dipper constantly having a jet nozzle spraying oil at it.
BTW, it has been my experience that GM did not stop using pal nuts when the dipper engines were phased out. They used them for a few years on insert bearing engines.
Last edited by 52Carl; 04/09/2024 1:30 AM.
