ok, we all know that there was alot of emission and cost saving stuff done to vehicles that harmed our precious mileage, if not we wouldn't know what air injection and cast iron manifolds are. so how about a list of stuff that can be done to help turn these around? such as recurving the dizzy, hot ignitions, headers, unobstructed air intake systems and electric fans. but what about stuff like chips, crank pulleys, and heck even abnormal asperation. but for once lets not even consider fish oils (synthetics probably ok) fancy gidgets and tv specials. and also assuming a well maintained vehicle, not to sound rude, but IMHO people that wont keep up maintenance shouldn't even be in this part of the forums
You are not going to get much of an improvement with an engine that has a distributor and a carb. All the emissions stuff was kind-of tacked on band-aid for cleaner air.
Computers and fuel injection with distributorless ignition changed all that. We can now have fuel economy, power and clean air all at the same time. And the engine compartment is much cleaner with less junk.
What we really need is a portable energy source that has the same amount of energy a tankfull of gas has to get us almost 400 miles on a single trip, and is cleaner than gasoline or diesel. No one has figured that out yet, but they are thinking harder now that gas is going up in price.
I still like the lowered profile tire, alloy rim approach.
Dave is dead on about EFI. Electronic fuel injection and ignition is self compensating instantaneously to correct the combustion process. Carbs and dizzies can err a lot, and are at best a rough approximation of ideal control.
The formula Vee approach to squeezing out more power is another good concept. By various means the energy required just to turn the mechanical mass of the engine can be reduced. Roller rockers and lifters, timing gears vice chains with an oil groove cut in the gear teeth to relieve pressures between the spinning gears, lightened flywheels, special additives to reduce friction, and numerous other tricks are out there.
All the way out to the wheel hubs - some bearings are better than others. Geo Metro's for example have sealed machine bearing cartridges instead of adjustable wheel bearings.
Standard coolant pumps can be replaced with electrically driven ones - but that is more of a strictly racing measure.
Definitely an electric fan with a thermostatic temperature control. A fan does not even need power above a certain speed. In fact - it's a pity electric fans are not made to serve as secondary alternators at highway speeds.
What about knife edge cuting of the crank to reduce weight? What if I could make a 351W crank weigh the same as a 289 crank? I might jsut rebuild my 302 If I can not find a good 390 and If I do I will set a 15 MPG goal for an early Bronco with 3.54 gears and 31" tires and 3 speed, yes I know more gears are better but I can get a fresh 3 speed for $480 and 5 speeds ate over a grand plus they are heavier. I might take the money I save from using a iron intake to invest in roller rockers this will be a stump puller where torque falls off at 3600 rpm followed by a rev limiter.
Suspension plays a role too, I have a frind who drove a truck with the front 3" higher than the back, he had EFI 700R4, 35" tires and 4.88 gears he only got 7 mpg, another friend had a similar chevy with a suped up 468 putting out 500+ hp and he got 10 mpg only difference was he had the rear end up 1" higher in the back, 3 speed auto and 34" tires and 4.56 gears, oh I forgot he even had a heavyer truck that was carburated holley 4 barrel.