Ignition timing for best gas mileage

I have an 87 Dodge Dakota V6, originally equipped with a Holley 6280
electronic feedback carburetor. The mixture control solenoid in the carb
went south a while back and is no longer available so I replaced the
6280 with a 2280, which is the non-feedback version without the mixture
control solenoid.

Recently, after installing the new carb and an MSD spark booster, and
adjusting everything to factory specs, I made a 200 mile trip which was
about 90% freeway and with a 1/2 mile gain in elevation.

I got 22.7 mpg. And this is with a heavy duty lumber rack and a 2'x2'x4'
toolbox full of tools and starting out with a full tank of gas. The
truck had about 113,000 miles on it.

I was really dumbstruck at the gas mileage I got on this trip and then
started to wonder how I could better it. The factory manual says
disconnect all the ignition timing inputs to the computer to set the
spark to 7 degrees BTC. That's where it is now.

Which way should I tweak the timing to get better mileage? Should I go 5
degrees BTC or 9 degrees BTC? I am especially interested in getting
better city mileage with lot's of stop and go driving. Can I expect this
by tweaking the ignition timing?


--

McCain -- it rhymes with Hussein, Bahrain, cocaine, insane, wolfbane,
chest pain and chow mein.

Samson wrote:
> I have an 87 Dodge Dakota V6, originally
> equipped with a Holley 6280
> electronic feedback carburetor. The mixture
> control solenoid in the
> carb went south a while back and is no longer
> available so I replaced
> the 6280 with a 2280, which is the non-feedback
> version without the
> mixture control solenoid.
>
> Recently, after installing the new carb and an
> MSD spark booster, and
> adjusting everything to factory specs, I made a
> 200 mile trip which
> was about 90% freeway and with a 1/2 mile gain
> in elevation.
>
> I got 22.7 mpg. And this is with a heavy duty
> lumber rack and a
> 2'x2'x4' toolbox full of tools and starting out
> with a full tank of
> gas. The truck had about 113,000 miles on it.
>
> I was really dumbstruck at the gas mileage I got
> on this trip and then
> started to wonder how I could better it. The
> factory manual says
> disconnect all the ignition timing inputs to the
> computer to set the
> spark to 7 degrees BTC. That's where it is now.
>
> Which way should I tweak the timing to get
> better mileage? Should I
> go 5 degrees BTC or 9 degrees BTC? I am
> especially interested in
> getting better city mileage with lot's of stop
> and go driving. Can I
> expect this by tweaking the ignition timing?

--

There are some power - and therefore economy -
by maximizing the spark timing. That doesn't
always mean setting the most you can get away
with, that means exactly the proper setting.
Advance the timing until you get pinging on low
grade pump gas. Then back of 2*. That's about
the best you're going to get without a dyno.

--------
..boB
2006 FXDI hot rod
2008 Mustang Coupe
2001 Dodge Dakota QC 5.9/4x4/3.92
1966 Mustang Coupe - Daily Driver
1965 FFR Cobra - 427W EFI, Damn Fast.