I am in the process of breaking in my OS.18 TZ and it is the most finicky engine I have ever break in so far. I know when a engine gets broke in it will run cooler but this is the hottest running small block I have ever broke in so far. I am heat cycling and it does not take near as long to get up to temperature then all the other small blocks I have broke in. But this is the highest performance small block I have ever owned. Will keep all posted. This whole site not only these thread seems like it sure has slowed down!