List more engine details to get a better answer. LA or Magnum harmonic balancer and timing cover? I suspect poor quality gas, vacuum advance moving too much or connected to an incorrect source port, or mismatched timing marks so your numbers are lower than your actual timing. I use 32 degrees to 38 degrees, depending on what set up and camshaft arrangement, and not including the vacuum advance. Usually a stock compression Magnum 5.9 or even 5.2 can use 32-34 degrees total mechanical advance and still run regular or mid grade gasoline, although some gas stations have poor gas quality so grades will vary. I run 92 octane premium in Michigan when I beat on my car, or when ambient temperature is above 80 degrees.
