Brian,
10 mpg is very low - approaching Humvee-like mileage. However, a run of
5-10 miles is not optimal to assess this. If you have stock needles,
headers, valves, air filters, wheels and cam, it seems half, or even
slightly less than that, of the mpg you might expect. Also, calculating
mpg by an estimated 'eigth of a tank' is putting too much faith in the
accuracy of your fuel gauge. Is your choke really off when the knob is
pushed in? How are your plugs. If they are as sooty as your tail pipe,
then you are running rich. But if you only drive 5 or so miles at a time,
the short distances could explain much of that.
I'd try a longer run, minimally 50 miles, on as flat a route as
practicable: first warm the car up, then top-off the tank, reset your trip
meter and then refuel at the same gas pump on your return. See what mpg
you really get, as the car is set now. If you have a gps, the recorded
mileage, while not perfect, may be more accurate than your tripmeter. On
your return, I'd look at your plugs; if sooty, check your timing, clean
your plugs, lean your carbs a little, then try again. BTW - are you
running stock plugs?
The damned, wretched pity of all this is that you'll have to drive the car
more frequently, for greater distances . Yeah!
I have a 62 TR4 with SU6 carbs. I get 20 about town and 25 on the highway.
I have no overdrive (yet). This seems about average with these cars, in OK
condition, with today's fuel, with moderate-to-spirited driving. In
Imperial gallon terms (in case you are in the UK) these mpg ratings would
be 25 mpg around town and 31 highway...very reasonable for a 46-year-young
motor. Less flattering things could be said of her similar-vintage driver
;^)
Good luck,
Brian
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