WhizzMan wrote: If you keep to factory specifications of your con rods and bolts, you should have some form of predictability on how likely they are to fail.
Hi WhizzMan, I share your need to understand what is logical or predictable when building an engine. My life experience has tempered the mechanical engineering education certainty I once had. If you add 10% more power to an engine, and drive the car once, the next time you drive the car it will be impossible the notice the difference. Most likely that 10% will be from a cam change that raised the peak rpm of the engine. The chances that the engine will now be driven at an overall higher rpm range are good. The stress the engine now sees will be more than the 10% that one would think. Now throw a missed shift at redline in just for fun. Or maybe passing another car after a long hot pull up a steep grade by dropping two gears and not noticing that you went 1000rpm over redline. If one uses this logic then putting together the best possible long block is not that hard to justify.
Keep in mind the rod or bolt does not have to break for the engine to fail. Stock rod stretch can fail a bearing before the cyclic loading breaks the beam. Have seen plenty of big ends that needed re-sizing because they were not round, or were tapered , or barreled if indeed they did not start that way.
I have spent countless hours grinding, polishing, and shot peening magnafluxed stock rods. Then replacing the rod bolts and finishing with a re-size before sending them out for final balance. What a waste of time and money. One can buy a far better rod for a reasonable price from many vendors who can specify a rod based on the max rpm the engine will be operated in. GC would be happy, I'm sure, to either sell or advise anyone on what he has proven to work.
WhizzMan I know that you can get a 10% gain in power without changing any parts in the engine. Doing a good valve job with valve detailing, cleaning up the bowl, good valve springs, and degreeing in the cam will show a predictable power gain.