only 12 in hg

[ckenwright]

Today, when I got home from work, I tried to tune the truck. I used a vacuum guage, timing light, and external tack. No matter how hard I tried, I could not get the vacuum below 12 in hg unless I went way advance. I finally settled on 6 or 8 BTC and test drove it to find that it knocked under full throttle. Could all this be happening as a result of having put a 4 barrell carb on a motor that had a one barrell on it with out changing the cam also? Any input would be appreciated.