1980 Aspen, 1945 carb with richened idle & power circuits, 9.7:1 compression. I pull the plugs every oil change. I was running a #68 jet for the past year, but moved to a #69. The plugs looked lean and an inspection mirror showed the exhaust valves white. Ambient has dropped into the 30s, but I suspect the gas formulation has changed. Car runs very well and gets better than 22 overall mpg, just don't want to ruin the exhaust valve seats. Anyone have a similar situation?

Mitch

I had to give the choke on my 66 Dart a little "tweak" to the rich side once the weather cooled-off. Also had to put a new set of plugs into the engine, I lost track on how long the last set was in there but they were pretty "rounded-off". The car runs much better and idles smoother with the plug gap back to where it should be.
DD

Just as a follow-up, the engine maintains a slightly higher manifold vacuum at the same steady-state cruise speed. So it looks like the jet change has resulted in less throttle needed for the same engine load. I'll see what this does to my mpg.

Mitch

Follow-up: the plugs now look just about ideal. Manifold vacuum went up from about 14 to just over 15 at a steady-state 65 mph @ about 2300 RPM. The car runs and sounds better. Fuel mileage has remained unchanged at about 24 mpg.

Mitch

what setup are you running besides the carb to get that kind of mileage? what kind of car do you have it in?

in the set up below(except for the carb, still have a 1920 holley on it) i can barely manage to get 20 mpg out of it. it doesn't matter how i drive it, easy, hard, whatever.

zedpapa

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1970 dodge dart w/225 /6 bored .040" over, holley 390cfm w/vac. sec., compcams 252s, clifford shorty headers w/2.5" exhaust w/flowmaster, f-body 11" front discs, aluminum A-833OD, 8 1/4 w/3.21 SG
soon to have 5 gears!!!

The car is an 80 Aspen with about 175K miles. 2.94 diff, lock-up 904, big 15 inch tires, stock shortblock with head shaved 0.080, pocket ported & stock cam degreed & advanced 4 degrees. I'm currently using an electric fan which is good for 1 1/2 to 2 mpg. I have spent a lot of time playing with the carb and distributor and the fuel & spark are about as close to optimal as I can get it.

Mitch