hey y'all,

i just drove my truck 1400 miles over the last couple weeks. it ran perfect, as always, and got ~13mpg through everywhere but ohio (i hate ohio for various reasons,but thats another thread all together).

when i got back to nashville, it was a bit chilly,and my truck was running kinda funny at idle. i proceeded to adjust my carb, to no avail. it had done the same thing in the colder weather in mi, ran rough and tried to die at idle in gear. a voltage regulator fixed that problem, but that was not the only symptom.

anyways, bottom line, i adjusted my timing. it was set at about 12° base,which gave good driveability, but bad cold starts. i proceeded to retard to about 8° base, and drove like a "butthole" (heavy acceleration) and alot of short trips on the next tank. tons of high idle colds starts and such.... much to my surprise, when i gassed up this morning, i adjusted my milage for the my tire size (31x10.5, 2.75 rear ratio, c4) and drove 305miles on 17.1 gallons= 17.94! i was quite happy with this, and wanted to share.

sorry for the long post, but i wanted to give the whole scenario. i noticed no difference in drivability, i ran premium on my trip when i got 13, and ran regular when i got 18. amazing what such a small detail can do huh?

figured this may help someone, feel free to ad thoughts

 

So all you did was adjust timing to 8 degrees advance instead of 12?

 

notyettoday,

Interesting !! What year vehicle and engine do you have? EFI or carb and if carb is it a 1, 2 or 4 barrel?

 

its a 77 f150 custom lwb 300 i6 all stock, with an open element air filter. no cat, single 2in straight pipe. all i did was adjust the timing... recent tune up, freshly rebuilt carb

 

I'm a little lost, why would you adjust your mpg for tire size and axle ratio?

 

speedo gear is exactly right with 235/75 r15, i have 31x10.5 on it now. odo reads 85% of a mile