wmjinman -
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Dunno how hard core you want to get about MPG, but my experience is that running at LOW rpms gives better mpg even if below the "efficiency peak rpm". But instead of getting lower gears and bigger tires, you can just get SMALLER tires. Again this would be a hard-core mpg play, not a "bad-ass looking truck" play, but smaller tires would also lower it and reduce aerodynamic drag.
Speaking of aero drag, depending on how much driving you'll do at highway speed, that is what will yield your biggest results (assuming the new engine runs well). And by "running well", I mean stock re-build - nothing fancy or exotic. You mentioned a bigger air dam. YES. take it down to the same height above the ground as the lowest hanging stuff under the car. Grille block: again YES. I got 2 mpg just from that. Block off as much as you can & not overheat. You might be surprised and be able to block almost all of it! Looking at your side mirrors.... again, for hard-core mpg and "screw the looks", how about getting some really small car mirrors on there? Then finally, build some sort of lightweight Kamm-back or boattail.
I know you are all into your engine mod ideas, but my experience is that as long as the engine doesn't run like crap and waste lots of gas because of that, the bigger gains will be from aero and hypermiling techniques. Of course, do the lightweight synthetic oil and remove all unneeded parasites running off the fan belt (and the fan itself, probably - replace with an electric one). And same thing with lightweight synthetic gear lube in the differentials, too. - and keep the tires aired-up to max sidewall or above.
Simple things like that will, I'm guessing, add up to more mpg improvement than the most exotic specially engineered high-efficiency engine would.
I'm reminded of MetroMPG's story (I think) about a 1st generation Honda Insight hybrid he got. Thing is - the battery pack was shot & he didn't want to buy a new one, so just disconnected all the hybrid-related stuff and got like 100 mpg out of it as a conventional gas car!!! See, it wasn't the exotic engine (hybrid system) that made the 1st generation Insight so great (although it helped - some), but instead, it was overall shape, size, and design of the car itself. I'll bet you could transplant just about any similar sized, modern efficiency gas engine into a 1st generation Insight and still get stunning mpg with it just because of the CAR, not the engine. So I say if mpg is your main goal, don't put so much effort into the engine, but instead, somewhere it'll REALLY help - like a boattail, air dam, grille block, etc, etc...
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Thanks for the reply
It has come to my knowledge that lower rpms will be more beneficial for my purposes, despite the common perception that higher rpms are more efficient for these engines and trucks. 2 reasons that is so -
1) Reduced load due to aero mods
2) Lean Burn
I am serious about improving fuel economy... but I do wrestle with wanting to make the truck look good at the same time! Oh the agony! Smaller tires are a possibility. I really want to run 17x8-9 wheels with 255/75R17 (32x10) Goodyear SR-A's. I can get this setup pretty cheap, lower cruise rpms and increase FE and looks at the same time. The 17s will have more weight than my 15x8 wheels, but it does open up the possibilty of running LRR tires down the road.
I'm planning on doing the air dam and grill block soon after it is back on the road. The mirrors... ehhh, that will take time to decide to mod. Same with adding a small kammback, even though the K5s have an excellent setup for adding this. Removable wheel well coverings would be in order as well.
I pulled nearly 17 one time (not very scientific, I know) by driving to Greensboro and back. With a tired TBI 350 with 15w-40 oil and a 700r4 with no lockup. This is before I knew the awesomeness of coasting, and the only thing I did was keep it around 55 mph the whole time. I had learned to finesse the throttle to make it run near lockup rpm levels. Knowing this, I do want to focus on drivetrain efficiency as much as possible while everything is out. Honestly, I think I can hit 20 mpg with
no aero mods. But they will make life easier, so they will be added after a baseline is established
I plan on full synthetics and minimal accessories. I'll have an alternator and a water and PS pump. Electrical fans are a must have. Shoot, I may run an electric water pump too... I'm just ready to get this thing back on the road!