I recently decided to run my vaccum advance off the ported (timed) port vs the manifold vaccum port because my engine was never happy with the vaccum advance on the manifold vaccum port, thuddin out the exhaust and i could never get my idle air mixtue screws dialed in right with it on manifold vaccum.
The way i have the vaccum advance can set now is to add 12 degrees of timing at 18 inches of vaccum. I have my initial timing sitting at 15 degrees and my total timing is at 33 degrees so i have 18 degrees of mechanical advance. So i'm guessing while cruising down the road at 18 inches of vaccum i'm sitting around 45 to 46 degrees of total timing. I have never really understood how to tune the vaccum advance on a ported source. So i tuned the vaccum can based on 18 inches of vaccum because thats what my engine produces at an idle and i set it to add 12 degrees of timing at 18 inches of vaccum and then put it back on the ported vaccum source.
Does this sound close enough? Or should i turn up the vaccum can to add 14 or 15 degrees of timing at 18 inches of vaccum? How many inches of vaccum is my motor producing while at a steady cruise going down the highway at 65? Is it producing more then 18 inches of vaccum? I just need some help getting it close, it doesnt have to be spot on but i'd like to know i'm in the ball park with the vaccum advance, i'm running 91 octane premium fuel thru it if that makes a difference on the timing from the vaccum advance?
The way i have the vaccum advance can set now is to add 12 degrees of timing at 18 inches of vaccum. I have my initial timing sitting at 15 degrees and my total timing is at 33 degrees so i have 18 degrees of mechanical advance. So i'm guessing while cruising down the road at 18 inches of vaccum i'm sitting around 45 to 46 degrees of total timing. I have never really understood how to tune the vaccum advance on a ported source. So i tuned the vaccum can based on 18 inches of vaccum because thats what my engine produces at an idle and i set it to add 12 degrees of timing at 18 inches of vaccum and then put it back on the ported vaccum source.
Does this sound close enough? Or should i turn up the vaccum can to add 14 or 15 degrees of timing at 18 inches of vaccum? How many inches of vaccum is my motor producing while at a steady cruise going down the highway at 65? Is it producing more then 18 inches of vaccum? I just need some help getting it close, it doesnt have to be spot on but i'd like to know i'm in the ball park with the vaccum advance, i'm running 91 octane premium fuel thru it if that makes a difference on the timing from the vaccum advance?
