I higher compression than 9:1 would help quite a bit. I'm aiming at the 9.5 range or whatever my cam designer tells me, that he can make work with regular gas. Look at the KB hypereutectic pistons, there are $315 sets that can get you in the 9.5 to 10:1 range. Set the quench in that .035" range with adjusting the pistons and gaskets, that should make good power.
The exhaust is horrendous, that's a cause for a big loss of power and fuel economy. If you could correct the exhaust, and make the compression/cam/intake ideal with PCM programming for proper A/F and timing, 21-23mpg should happen with the 302. But without all of those things right, you'll be lucky to get close to 18mpg. Nobody as yet has corrected the exhaust in any of these 2nd gens, and I might end up being the only one to do it.
Going along that route is possible, but costly and is only going to be really successful if done by very capable skilled tuners.
What you're not mentioning for example is the entire aspect of motor management and PCM programming.
And that needs to be optimized for the engine and the changes on the engine for it to end up being somewhat fuel efficient. But aside from a few rare PCM reprogramming applications which improve fuel efficiency at the cost of a mild loss of performance, most motor tuning just increases an engines the power and with that also increases fuel consumption.
What you'd "ideally" want to improve fuel efficiency would be modern things like variable valve control, a start stop automatic system and things like that. Those kind of features could really improve MPG noticeably, but those are practically just plain impossible to implement in an existing older engine.
There is one other thing that could help reduce fuel consumption considerably though, replacing the transmission with a manual transmission geared for optimum fuel efficiency rather than performance.
With the exception of very few of the newest automatic transmissions
engineered by Mercedes and subcontractors, all automatic transmissions have a little bit of constant slip as well as added friction. Manual transmissions are more fuel efficient on paper.
Practically they do require the drivers to adapt their driving style and habits to achieve optimum fuel efficiency though. Sadly they tend to make people drive their car a little more sporty instead and that can easily be counter productive as well.
Other than that wheels and tires can also make a significant difference and items negatively affecting the vehicles aerodynamics, like roof racks etc.
And of course there is also weight reduction. Our explorers usually carry a LOT of weight that could potentially just be thrown out. Stuff like unused rear seats, insulation, carpet, plastic covers on doors...… You know, all the stuff you typically won't find in race cars.
) and call it good. Seriously. You can thank me in 15 years when your still driving it and saved enough to buy a used Shelby for cash in that time. Or you could buy a Shelby for cash sooner if you drove a four banger. Or you could just find a way to make more money. Or steal a tanker full of fuel 2F2F style to offset the cost of the mods you have planned. Many thing you can do..
