[chiphead]

I've done a LOT of governor tuning with TH350s and 400s. What you do is, get the shift points close with the weights and then select springs to set shift spacing and fine tune the shift points. Only change one weight or spring at a time and take careful notes. Drive the car at least 2X with each change, at part throttle and full throttle to judge the impact of the change.

If you're happy with the spacing between shifts but the WOT RPM shift point is too low, you'll need to reduce weight from the inner weights. Take the governor weights out, noting which spring went with each weight. Get a scale that measures in grams and weigh the weights. Shave 2 grams off the heaviest weight, or change to the next lightest weight in the kit, reassemble and re-test.

You'll need to do this several times to sneak up on the settings. Once you get it shifting at part throttle and WOT close to where you want it, then play with the springs. Lighter springs raise shift point RPM, heavier springs reduce shift points. Springs close in tension will stack shifts together, but a combo of heavy/light springs will move the shift points apart. That's why you have to take careful notes, as its easier to get lost in what change did what.

Keep in mind that both weights and springs affect all shifts, not just WOT. If you get the WOT shifts close to where you want them with weights, but part throttle shifts are early, you'll need lighter springs. That will move your part throttle AND WOT shift points up in RPM. So watch the trend in the behavior. If the WOT shifts are not quite what you want, but part throttle is too low, then start tuning with springs, because the lighter springs will move everything up.

Any valvebody/plate mods, torque converter efficiency, modulator setting, line pressure, governor, kickdown all affects shift points, so you've got to take them all into account when setting up a transmission. Work your way to the governor and then make changes there.