Line bias valve
I've been researching the purpose and function of the line bias valve. My parts for the buildup of my 700R4 are on the way and as I prepare to put this unit together I wanted to be sure that I have everything as close to right as possible. In my research I found an article from Bowtie Overdrives that explains in a general way how the line pressure management system works. The line bias valve's role in this system is to "tune" line pressure rise to match the engines torque increase with throttle opening. The GM engineers intended that most line rise would occur in the first 50-65% of throttle opening, as this is where engine torque increases most in stock applications.
You can understand how our modified engines might want different tuning in the line bias valve. By blocking the valve in place, we delete this bias tuning so that line pressure will rise in a more linear curve from closed throttle up to WOT. In my case, my trans had a bang 1-2 shift at light throttle, and seemed to have a soft 2-3 shift at 1/2 throttle. I am going to use a smaller accumulator valve to help the 1-2 shift and I think that blocking the line bias valve might be the right thing for me. If my full throttle shifts end up being too harsh, I can always go to a stiffer spring instead.