Timing for economy driving?

[cfan10]

Ok, another quick question, what degree timing is perfect for best economy and city driving? Thanks in advance for your input.

Info:
’84 c10 305v8/th350
dual exhaust
edelbrock 1406 4 barrel carb
supercoil

[jjmorrse]

Several people on this site, such as Rich Weyand, knows a lot about sbc timing in these trucks.

Since the variables add up in each individual truck, the best for yours might vary from someone else's. Climate and elevation are also factors that affect ideal tune.

I would suggest taking some time, then start getting familiar with your current vacuum readings, then move on from there.

First it might be helpful to make sure your cooling system is good and can keep your temps stable. Although a lot of hot rodders like a low temp thermostat, for economy you might want a little different temp. The more stable you can keep the operating temperature, the more precisely you can tune without worrying about overheating or knock.

You actually have three timings: Initial, mechanical, and vacuum. For best power and/or economy, you want to make sure each adjusted. That takes a little time. Some switch from ported to manifold vacuum when they tune. Lots of threads about timing on this forum. On relatively stock vehicles, here is not a lot of difference between tuning for power and economy, as I understand it.

Some people are fans of electric fans (sorry, couldn't help it). Although there are losses associated with conversion from mechanical to electricity energy that people sometimes don't consider, an electric fan that is off isn't a power parasite, but a mechanical fan is always creating a little engine drag.( There are differences between mechanical fan and clutches as well that can make a difference. Some HD fans had steep pitch blades and a lot of drag, which is great for cooling, not as much mpg.) In colder climates, or on the highway, an electric fan that is not running most of the time might add up to some mpg savings. In the desert, in the city, maybe not as much, since the electric fan would then be kicked on more, so the alternator would be working harder to keep it fed.

Different tires have different rolling resistance. Underinflated tires cost mpg. Check wheel bearings and brakes for drag.

The air dam underneath the bumper may help some, I believe.

Overdrive trans, towing torque converter.

Rear gear ratio.

Don't brake when you can coast. Don't accelerate abruptly.
These things together could add up to a lot of difference over time.

Sorry, I went a little overboard. Back on track,... If I were dialing in my truck, I would get out my vacuum gauge, timing light, and tach, look up some of Weyand's advice on older threads for a baseline, and spend a weekend or two adjusting initial timing, mechanical weights and springs, total stops, and vacuum advance. Some use an adjustable canister, others have a specific part number canister they like and just put it in.

At the end of the day however, these trucks are heavy, and the engine design was from the 1950s so there is only so much one can do to increase gas mileage, outside of the DAPOW mod.

DAPOW = Drive a Prius on Weekdays

I hope some of this might be helpful.