Thanks very much, Wittsend, for your comments. Reading your responses to my questions, I see you know a lot more than I do about each item. I will rethink, based on your input. My hope is to research as much as possible and go in with solid ideas. Your comments helped tremendously. I hope to clarify things here.
Porting and polishing. Yes, I can see where porting too much would reduce mileage.
Good point on turbos and superchargers. I had the same thing in the back of my mind. You need rpms, especially with turbos, to make more power (and turbos requiring less compression). You're right, what I need is not rpms, but low-end torque.
Looks like I'll be seeking out the OHC 2300 and the 5 speed from a Turbo Coupe. I'm glad all were carb engines. I can actually work on them and it's not terribly expensive.
The tube frame, crew cab truck is a very unusual idea, I admit. The thing is, I can control the weight, width, length, balance and aerodynamics. If it was absolutely necessary, I could make doors and borrow some windows from another vehicle. I can't make glass. A 'for instance' is my Kelmark GT kit car, inspired by Ferrari Dino. It uses Pinto door and window mechanisms and windows. It also uses a Pinto windshield.
It is an odd application. I'm looking to make a highway vehicle to suit my needs. My trips between states here in the southwest is 540 miles each direction. Gas gets awfully expensive considering these distances. A few percent gain in efficiency over these long distance add up to decreased costs. Occasionally, I need to haul light but oddly shaped furniture, appliances, etc. A station wagon or minivan is not quite right for the job; it has to have a truck bed. Also, lots of interior room is needed.
My old Geo gets 46 mpg, but it doesn't haul much. It did do a full size recliner without propping open the hatch.
I need to meet the aforementioned specs while maximizing economy. I think I can get far more mileage and build this truck much cheaper than buying a crew cab truck. In addition to being very pricey, they guzzle the gas.
I don't need to accelerate fast at all. One highway; straight shot. I just need good top end economy and to deal moderately well with slight uphill grades. Cruising around 75 to 80 would be great, although I know the law of decreasing returns kicks in when speed is pitted against mileage. No off-roading is needed, so the vehicle can have a lower stance. It could stand like a car. Being lower to the ground improves aerodynamics.
About rotating mass. When cruising, more rotating mass/angular momentum will preserve the energy from each piston stroke and can enable you to very temporarily store that power in the form of angular momentum - and then draw upon it. I learned this first hand in India from watching a building crew use a weak, old single cylinder engine for a pile driver. Once the engine got going, the little horsepower and torque it had was preserved in the flywheel and kept elevating that pile-driver until drop time. If you're familiar with hyper-mile fuel saving techniques, this helps with the pulse on/off technique, which means you're on the pedal then off the pedal - pulse with a little gas and glide using your built momentum. When accelerating, it takes more energy to get all of that mass moving. It is a double-edged sword. I only need steady highway speeds over long hours. Acceleration and deceleration will hopefully be very infrequent.
I can see where the progressive 2bbl would be a good choice. I do have a Weber 32/36 lying around. It fits a great, great number of intakes. Let's hope it fits a Ford intake for the 2300.
Air conditioning, unfortunately, is a must. My destination city is above 115 degrees in summer. Temps in my portion of the Mohave Desert exceed Phoenix or Vegas temperatures. Temps on the other end of my route reach below freezing.
Good thoughts on the cam. You're right about the power range.
Good thoughts on the rear end ratio. What ratio might you suggest?
And about compression: My thought was a stronger bang for each compression cycle to increase efficiency. Does that idea have merit now that I've dropped the turbo or supercharge idea? What I was asking was regarding a maximum reasonable compression level that won't keep me blowing the head gaskets all the time. The idea is to increase compression to eek out more power, but still allow for a good engine life.
Your suggestions helped clarify things. I hope my reply helps clear up some things. Do you have other suggestions? Open to suggestions from all.
Deep Appreciation,
Tyanite
