could be the advance curve in your 6.9 distributor is way too enthusiastic
maybe clippings the wings of the light spring will slow down the advance to stop the ping.
This thread is about AC regas, not what type of fuel you put in the tank, or a radiator cap. Stick to the subject please; if you want to discuss something else start a new thread
This thread is about AC regas, not what type of fuel you put in the tank, or a radiator cap. Stick to the subject please; if you want to discuss something else start a new thread