Like Joe (ZFD), I also had very good luck running the same stock Norton rods on 750 and 920 road race bikes for several seasons. I did have the rods initially inspected and shot peened, and thereafter inspected at teardowns, which were typically once a year (or more often if something went bad). I never had a stock alloy rod fail. I did have one of the factory steel short stroke rods fail, but that's another story, and they are pretty well known now as failure prone.
However, I have seen stock alloy rods fail in other racer's engines from fracture at the small end, and have found a couple during inspection to have a web of hairline cracks below the pin bore. The cracked rods were from race engines I acquired from others, and don't know the history of, so I can't say how much they had been abused. Neither of the cracked rods had been shot peened, and I'm pretty sure they were already well used when the engines were converted for racing.
The conlcusion I would draw from this is that stock rods are not indestructible, but are fine for racing as long as they are prepared properly and are regularly inspected. The other alternative, which used to be pretty common practice among serious racers, is to replace the rods with new ones every season or two. That was back when the company was still in business, and replacement rods were available at your local dealer for a reasonable price. One could follow the same practice now with rods readily available from Andover.
Having said all that, I'm also a fan of Carrillo rods because they really do seem to be indestructible (at least in Nortons), and I don't have to worry about replacing them periodically. Re-balancing the crank for them isn't much of a drawback, since I would be balancing any crank used in a race engine already. The stock rod does have the edge in small end weight, although Jim's long rod kits come a lot closer than the standard Carrillo rod for Commandos.
I did build one big bore engine with titanium rods, and it survived AMA Twins racing at Daytona, as well as several runs at Bonneville, one over 150 mph. I suspect a properly designed titanium rod would have the lightest small end and a total weight close to that of the stock rod, but I don't know how long you could safely use it. I've heard conflicting views on the fatigue life of titanium rods in racing engines. There might be something to be gained here, but it would take deeper pockets than mine to experiment much with ti rods. The titanium rods for Nortons that I've seen are heavier than stock rods, and also have a significantly heavier small end. To develop something like Jim Schmidt's lightweight kit with them would require some serious analysis and testing, and the end product would be a lot more expensive.
Just passing along my own experience. Your results may vary.
Ken
