ALL rods have a finite number of laps in them regardless of material.

One of the local go to roundy round builders here uses steel rods of the caliber being discussed for his dirt modified engines.

He tells his customers they are done at 600 laps. Anybody that doubted him has found that they had a $25,000 doorstop before they made it to 700 laps.

Is there a difference in the stress cycle count between WFO and 1/2 WFO? I would say absolutely, but I don't know how you would quantify it. If you call BME and tell him how much your pistons weigh, how much spray and how many RPM you're going to twist it, he will give you a lap number to change them out at. He would likely have some kind of formula to calculate how much to reduce that lap count by to compensate for the street miles.

Kevin