Correct, completely stock distributors, you'll both get to the same place. The 69 Distributor will be at 19-23* @ 1800 RPM, and so will the Stage1 distributor, 10* initial + 9-13* mechanical. Then, 30-34* @ 4600 RPM.
I looked around before I'm asking this question and could not find the answer- What should the initial timing be on a 70 350 ?
Unless I am doing something wrong; using a digital timing light it is 25* with the vacuum hose plugged. It is a unknown HEI .
Impossible to answer that in 2024. Why? Because the car you are asking about is now 54 years old, and the specs below only apply if it has the factory installed distributors, #1111986, or 1112006. What are the chances of that? Unless you have owned the car from new, and know for sure, chances are the distributor and other engine components have been changed. Different distributor? The specs below go right out the window. Same answer, unknown HEI, unknown specs unless you can get a part number and look it up in a Buick Chassis Manual. It could have still been modified in the past. HEI's typically had too much mechanical advance built in, and they didn't allow maximum advance until at least 4000 RPM. You may not be revving it high enough to see all the mechanical advance. Changing the springs to the lightest available springs will let you see all the mechanical advance at low RPM.
Thank you for your help. I will order some lighter springs. I am going to reread your tuning thread - do you suggest an adjustable vacuum advance as well? The on the the distributor looks very old; since I have it apart....
You'll only need an adjustable vacuum advance if you intend to bring the mechanical advance in much earlier. You can modify a stock vacuum advance if you like. Everything is in that first post of the thread.
If I understand correctly , the purpose of lighter springs is to bring the advance in earlier. Does the vaccum advance aid in increasing the advance rate ?
Vacuum advance operates on engine vacuum. At light throttle/load, engine vacuum is high. At high load, vacuum is low, and at wide open throttle (WOT), vacuum is at or near zero. The vacuum advance canister has a spring that opposes vacuum pull. To advance the timing, engine vacuum must overcome spring pressure. The vacuum advance is a load compensating device. At light loads/cruise, the engine can tolerate more ignition advance, and that results in better fuel economy. At high load/WOT, vacuum drops and the canister spring wins out pulling out any advance that the canister generated. The mechanical and vacuum advance operate independent of one another. All of this is in the very first post of the Power Timing thread.
