Originally Posted by RapidRobert
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I don't know how to tailor the vacuum advance to my engine at cruise speed. Can anyone please describe the theory on that?. I have always read it wants more that the 35* while cruising on the highway. I speculate probably 12* to 18* more, but how does one know what is optimal at steady state cruise and how does one test for that???.
add vac adv amt till you are just under the pinging point in everyday driveing under varying load/RPM conditions on your hottest/driest (most likely to ping) day & the same on a steady interstate cruise (also on your hottest/driest day) & peoples' hearing varies & there is silent ping so give it a cushion. You want to be close to that line but never over it.


This is where the laptop tuning capability of the Sniper really shines. Get a buddy to sit in the passenger seat as you drive down the road and you can adjust the ignition timing while you drive. As you slowly add timing you can watch on the screen as the engine uses less fuel and drops in temperature. You just keep adding timing until it starts to tell you that it doesn't want anymore. Then you go smooth out the transition so the timing will drop back down as soon as you get into the throttle. You can do the same thing with a mechanical distributor but it takes a lot longer.