I tend to hear that as well. "My dyno is pretty conservative..."
I know for a fact that there are two dynos within 50 miles of me that read 100hp different from each other.
Dyno numbers sell engines, plain and simple. The majority of engine customers don't know if their engine is 500 hp or 550hp....and if they have never been behind the wheel of something stout, then they may not know the difference between 400 and 500.
It should be pretty simple to spot if you look at the components. A guy brought me a 482ci BBC on Saturday evening that had spun a couple of rod bearings. It had a GM Performance crank, factory truck rods, Procomp heads, and a solid roller cam. The builder told him that it was a 750hp engine.
