Quote:

---

Here's how I'd build a super-duper mileage old mopar w/v8 (let's face it...a slant would be a better endeavor for mileage...but should you want a slant, apply much of what is here to it):

Start with the lightest available platform with easy access to parts...for a v8, the 64 A-body comes to mind.

Weight is CRUCIAL, especially with city mileage, and important out on the hwy...grades, minor acceleration, rolling ressistance are all heavily influenced by the weight of the plat-form you are using.

Another reason size is important, is that it is the second most important aspect when determining WIND RESISTANCE (speed is most important).

But going this way, you are minimizing the two most important things with regards to fuel mileage.

Face it, cruising at a steady speed, you need to apply as much hp as there is ressistance (more and you accelerate, less and you lose speed). When HP=rolling resistance+Wind resistance, you have steady state cruise. Increase speed, Wind resistance goes up exponentially, HP demands go up too. Increase weight, and you effect rolling resistance, AND you increase the amount of work needed to accelerate to speed, and to ascend hills either slight or great.

And HP will take a relative amount of gas and air...since really, that is the "work" that HP is calculating.

Given it's a v8, I'd go with the 318. In the ideal world, a 273 WILL have greater operational efficiency at a given speed/rpm/HP demand, but I think that this is more than off-set by parts availability and price.

Given this, and in keeping weight in mind: I'd build a roller 318 with eddy AL heads.
Give me 10.5:1 compression
Eddy AL heads (reduce pumping losses, relatively small ports will maintain intake velocity, wt loss)
Performer or LD4B intake (wt is the key here)
Eddy 500 carb ( tuned to idle as lean as possible, cruise on a slight hill with as little lean surge as possible...I'd aim for roughly 15-15.5:1 AFR).
HYD roller cam specing ~192-196 @ .050, roller 1.6:1 ratio rockers. Ideally lift in the .480 range.
1 5/8th headers
2.5 inch dual exhaust with an X-pipe.
Electronic ignition running 14 degrees initial, probably 34 total, in by 2200rpm...and as much vacuum advance without pinging.

For the tranny, I'd source an AL OD 833 (light weight and more efficient). For the rear end, I'd source a 7 1/4 rear with 2.94 gears for a 2.2 final drive ratio (lighter rear/gears/axles reduce losses/rolling resistance on several fronts...the closer to 1:1 a gear is, the more efficient it is with regard to frictional losses.)

I'd probably get an underdrive pulley set, have manual steering and no AC. I'd use a clutch fan too. A slant six radiator would have to do the job. Run a 205 degree thermostat. Heck, I'd even run a small battery to reduce weight.

Make sure the wheel/axle bearings are in good working order and adjusted correctly. I'd probably WANT 4 wheel drum brakes to reduce any drag on the wheels too.

For tires, I'd run what the insight runs...bridgestone potenza re92 (iirc)...very low rolling resistance. Inflate to 50psi (it's safe, however not recommended).

See where else you could lose weight. Run thin 5-30W synthetic oil too.

...

---