I only found bits and pieces on this in old posts. I have a Goodwrench 350, 4-bolt mains that is pretty much the way it came out of the crate. How hard is it on the engine to be in the 5000-5500 rpm range for a couple of seconds? Where do I get into danger of bending a valve or pumping up the lifters or something else? During normal driving I keep it under 3500. Ocassionaly, I'll shift it up at 4200 or so. I'm just trying to get a feel for where I start being really hard on the engine and where I am in danger of blowing it up.