So very stuck...

Killer6 said

I'm not sure why You want to change the spring, the allen screw should allow enough range of adjustment, unless it's some odd option app.
Ported is going to respond to the airflow/throttle position balance. If You're at 1/3 throttle on the level cruising @ 2800rpm, more air will be flowing & the vacuum will be higher(light load = more vac adv.), than 1/3 throttle climbing a slight grade at 1850rpm(heavy load = less vac adv.).

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So I can open my can all the way to the 15* it allows, as my rpms dont go high enough for the timing to be all in. My O/D and L/U make sure of that. My timing comes all in at 2200 rpm. But my cruising rpms are at 1600. I dont race this truck so I really never see 2200 rpms unless passing when I turn off the O/D and L/U. And it's not for that long. Almost all of my shifting happens between 1700 and 1800 rpms. Opening up my can all the way allows the motor to use what ever timing it would need without ever reaching a point where it would start to ping.