Originally Posted by bubbahotep
Cruise in 4th gear at 2500-3000rpm is 15.8 with no load at all (My understanding is that this is way lean)
Where Im wrong correct me but I thought I need 12.5-13 overall as a good AFR. So at cruise Im too lean, I have holley 73 primary jets and was going to increase those and then readjust my idle screws accordingly?? My existing powervalve is a 5.5 based on my 11hg idle vacuum, its a vac secondary carb with the yellow spring. 3310-c carb
Disclaimer: I am not an expert
12.5-13 is not a good AFR for anything in between the smallest throttle openings and WOT. Your 15.8 at level road cruise is actually almost ideal. It is near the AFR where the most power from the least fuel is found. This produces the best fuel economy. Between 10% and 60-70% of load whatever the leanest AFR which can be run without surging or popping is correct. The fuel curve if plotted on a graph would look like a bell with 12.5-13 on each and and 16.5 in the middle.