Re: 1966 GMC 305 V6 Service
Strange road trip 305E V6 HWY milage.
1. 9.3 mpg (about 60 mph I-75)
2. 17.1 mpg (about 70 mph I-75)
3. 16.7 mpg (about 70 mph I-75 return trip)
4. 9.5 mpg (about 60 mph I-75 return trip)
Mileage calibrated against map quest.
Triple checked full tank when I got the 17.1 mpg; even saw gas in tank through filler neck.
Thought I was home free until the last 9.5 mpg reading.
I suspect the carb or distributor is misbehaving under 70 mph.
Maybe I'll advance timing a bit more than stock and verify timing advance is functioning. I'm a little suspicious of carb power valve function.
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