20 plus mpg question

[cortcomp]

With the stock (well worn) 327, 3.73, and factory 3 spd, we drove home from fresno, ca to youngstown, OH, in my longbed 66. The carb leaked so bad the whole time that there was always a small puddle in the front of the carb on the manifold. Now, think after driving 12-15 hours a day, how warm it is under the hood right on the engine, and how much you need to leak to keep a puddle there from evaporating. We also found later that the fuel line from the hardline to to the pump (little flex line) was leaking air and sucking so bad, that if we pulled off the highway, sometimes it would stall and lose prime and we'd be lucky to get it going again before rolling to a stop. (we got pretty good at it.) We didn't trust the fuel gauge, we'd stop about every 100 miles.

So, driving 99% interstate, at a dead 70MPH (per gps, 75 per speedo) all day for hours, we had plenty of tankfulls to do the math with. We averaged 12.5-13.5 per tank. That's the 4bbl, and i know all 4 bbls were cracked (not WOT but open) to maintain that speed. When the motor was tore down, the builder said the walls were well scored and needed to go to .060 over, and the valves were beat back into the head. It ran great, but obviously well wore.

With a newly rebuilt tight motor, adding stick over drive (so can cruise staying out of the secondaries), keeping a factory style cam for good low end and low hp=less fuel, fixing leaks, pro rebuilt carb, etc, i see no issue why i can't come up with a solid 15-17 or even close to 20 the way i baby cruise around.

The key is to have a 4bbl and stay in the primaries (more throttle response and economy with front 2 bbls of a 4bbl than the 2 larger bbls of a 2bbl.) or FI but i don't think the standard 2 big bbl TPI setup will do much better than a well tuned carb., a factory style cam that favors low end torque over HP numbers that you can brag about, and then gears, tires or OD that will give you those low rpms at your cruising speed. That's a good chance.

Of course, you could just put the 4.3 vortec v6 in and be done, i had one in my beatup astro van that had a wonky tranny that lockup didn't work in, 220K miles and 22mpg all day everyday for several years. It's about the same level of (non)aerodynamics.