I have built some AMC motors and have follow Larry Mitchell's advice on them. I have had the priviledge of having Larry build my first AMC motor a few years back and can attest to what he is saying about the pinging problems of these motors. Larry rebuilt a 1970 390 V-8 and actually followed his own recommendations. As most know, the 70 390 is the most powerful of all of the 390 built. To this day, this motor is reliable and powerful. Being in a 70 AMX, it can light up the tires in just about any gear. I followed his recommendations when myself and a friend built my next motor, a 401. Got the same result and the motor found its home in a 71 Javelin SST. Although I do have to use a octane booster in my 70 AMX, I buy the stuff from AMX Enterprises and the stuff really works. The octane booster contains a certain percentage of good old fashion lead and depending upon how many ounces you use, you can adjust your octane levels by using this stuff. I currently run on premium gas (91 octane) and somewhere between a half quart to a full quart of the booster. Stuff aint cheap, but it is real good insurance from premature wear and tear. My 401 is ran on premium pump gas with about half of quart of the stuff. Both engines are running fine and I have not any problems with them in the last 5 years of running. I do not race and that was not intention when the motors were built. Just some decent street engines with an occassional woop *** on a few Mustangs from light to light.