My thinking is that if it's been working previously without difficulty, then it's probably still healthy and disturbing it is playing with danger. If it had a problem then it should have outward symptoms. Sort of like "if it's not broke.....then don't mess with it."N9149A wrote:... Just like you can't confirm for sure you have good bearings before you dissassemble a connecting rod for example. ...
The engine mfr'r provides a torque range for engine assembly. Most rebuilders aim for the middle of the range. The hazard in a partial-life engine is undertorque. This is due to several factors. A thru-bolt uses the opposite cylinder or case-halve for the compressive resistance. That opposite cylinder was installed with a rubber O-ring at it's base which was compressed during engine buildup, and the case-halves were put together with thread and sealant. Years later, that O-ring is completely without "rebound" and the thread/sealant is compressed and has taken a "set". The fastener it'self was also "stretched" as a function of it's original torque, and has likely taken a "set" over the years. Additonally the threads are doubtless not as clean as they were when "new", and therefore will require more torque to achieve the same actual effect as previous. Also, the main and rod bearings have "wear" and have given up some of their original thickness. A new cylinder will be installed with a new O-ring which will have fresh dimensions and in need of compression. Therefore if the exact same torque were used to reassemble that engine as previously existed... then the engine will have been reassembled with less compressive force or torque, less bearing crush, and more liklihood exists that a spun bearing may occur.
That is my logic, valid or not.
.....Brad