"The little black truck"...

[freebeard]

Could you elaborate more? Perhaps a link to an image? I am struggling to follow.

Search Google with 'GMC half-tonneau pickup' and the first hit is a very helpful aerohead posting:

Modding a pickup

...and on the Gale Banks website I find:

Don't ignore aerohead's post just because I posted the picture. It maps out a lot of possibilities for a pickup truck configuration.

Wikipedia says the half-tonneau was was OEM in 1998 on the Chevrolet S-10 EV

I know none of this answers *why* it works. I'm going to stick with

The air spills over the back of the roof and pushes on the back of the cab.

Another great permalink from sven7:

US Pat 4,573,730. 4 Mar 1986

[Sven7]

While the half tonneau should save you an mpg, you might think about putting together a plywood aero cap, as bobo333's 1977 Ford F100 sports. Shouldn't cost too much money and will probably get you two or even three mpg. I know, not much, but with a baseline in the low 20's it's going to be really tough to get much improvement.

What's your goal, fuel economy wise? Just minor improvements that look stock, or making it as efficient as a midsize car?

btw
http://www.fueleconomy.gov/feg/Power...WD&srchtyp=ymm

[slowmover]

I see a lot of ecomodding ideas, aero, etc, but not as much in discussion about the basic mechanical and "tune up" areas. I see a lot of older cars being modded here, but seldom does mechanical maintenance come up in discussions?

There may be the assumption that the owner has already "baselined" the vehicle. I consider that starting with a set of certified scale tickets:

1] Driver, full fuel & all items that are aboard permanently: Total weight adduced from two axle totals
2] Weigh each side of vehicle to get individual wheel positions.
3] This is total of three scale receipts: At a CAT Scale

Tire pressure dialled in from vehicle manufacturer data and RMA book (see CapriRacer's site: Barry's Tire Tech). Basically, a 15% load reserve above load versus pressure table (that fits within vehicle manufacturer range of pressures).

With that, proper alignment (painstaking). Wheel bearing service and proper preload (this is more open to interpretation than it should be). Same for no brake drag on calipers and fine adjustment of rear drums + emergency brake actuation.

Zero steering wander: KENWORTH (among others) cites excessive number of steering corrections per hundred miles as a source of poor FE. Rebuilding the steering apparatus should be high on list. At the same time, other front end componentry and body/frame bushings.

Rear spring sag. A lifetime of being torqued over in one direction can cause rear springs to have settled unevenly. Luckily, leafs are basically cheap.

Any adjustments in FSM to the auto trans? Are shift points at recommended rpm?

Obviously, all new fluids, filters, belts & hoses. The cooling system needs real attention for FE. Non-EFI motors have a hard time with temp regulation. So start with a pressure test. Etc. And use some RMI-25 to gently clean as you drive. I've used it more than 20-years.

Yes, sounds like valve stem leakage. A rebuilt head isn't all that expensive (as valve stems are a PITA given old tired springs also present). A compression test before & after. And a blowby test. If any cracked rings, then . . . .

Etc.

As I mentioned in another thread, do new seatbelts first, then brakes/tires. Safety, then FE, as they work in tandem with one another in this pursuit.

A new windshield for a vehicle with over 150k is also good. Clean with muriatic acid at 1:50 water (if you're brave) if no cracks. Frankly, they tend to be "sandblasted".

Next item is all new fuses & relays. New lamps, interior & exterior. Run headlamps off of a relay-driven BATT power (13V at lamp; see Daniel Stern site) to make things bright. Check voltage at rear lamps (and consider some kind of decent LED upgrade, not just pop-in lamps in housings not designed for same).

And ETC, again. The list is never ending, but the basics should be covered as above, IMO.

.

[oil pan 4]

At least quote a new windsheld, I was surprized to find I could get one for my suburban for $160. I had them put it on the next day.

[freebeard]

While the half tonneau should save you an mpg, you might think about putting together a plywood aero cap

What I found interesting on the chart you posted was the 'wing + cover':


It is 3/4ths as effective as the aero shell and gives a lot more access to the bed. The results for a partial cover with and without the wing suggests that the air moving past the sides of the cab has a lot of effect. Are there any examples of a Bonneville style spoiler on the back of a pickup truck cab?

Or maybe we should ignore the chart because it shows the partial cover as less effective than the full cover. And does 'basic redesign' mean anything?

[Sven7]

Good comments on tune-up. Might want to get it professionally aligned in case there are camber or caster issues, aside from toe.

Wing+Cover could be interesting but I get the impression you'd spend as much time getting the right wing angle as you would simply building an aero shell. And with such low baseline MPG why chance it? Kach22i on here has a wing on his S10 but it's not tuned for efficiency. He claims better highway stability.

I would go for the proven stuff if it's only going to add a few MPG. That is, either a partial cover or an aerohead or BZP style aero cap.

"Basic redesign" assumes you are a company putting out a new generation of the truck and you will be changing the actual sheet metal of the vehicle. I suppose this would also apply to those who build custom beds, like (I believe) SkyKing and his Dodge Ram.

There has been talk about turning a step side pickup into an MPG champ because the narrow bed gives you a head start on plan taper. I've also yet to see someone build a custom aero bed with covered wheels and everything (narrowed axle maybe?) so perhaps I'll have to do that myself some day.

[freebeard]

I spent $200 at a street rod shop once to get an alignment done on a VW Type III Notchback. The car was nimble and never failed to go where I pointed it. The shops gone; and I don't know where I could get work like that done on the car I'm driving today.

The thing about 'basic redesign' is that the bar is completely filled from 0 to 20%. So it's saying might not do a thing, might be as good as a full aerocap. Then they don't show 'basic redesign' + aerocap.

perhaps I'll have to do that myself some day.

It's so hard to get other people to build the vehicles you want to see built. Do you know what a 'bobber truck' is?

[Backtobasics]

Well, the abismal first tank is in....
13.36mpg.

This is not entirely unexpected.

After last fillup, I had planned on commiting to driving it daily. However, after a couple days of fighting it, on the way to work one AM, it fought me to go 65 on the highway, and steering wheel was a fight. I pulled over, and it was smoking from the right front wheel. The brakes were dragging, terribly.

Over the last couple week, it has received all new brake calipers, hoses, and pads. All the caliper and pad slides were lubed with synthetic slide grease, and I installed ceramic pads. I would like to have done the rotors (I have them too), but the front hub bolts to rotors, and bolt heads are beyond saving, so it will have to wait until I can use shop torch and replace. Calipers got a hit of red paint, and she is back together. Work commute starts tomorrow, and we have a fresh fill up in it. Temperatures have dropped into the 30's, so that will be taken into account.

[Backtobasics]

Once she proves reliable, I am going to start dialing in the carburetor, etc. Short term are to clean out interior beyond the basics, nitrogen the tires at work to max pressure, and start adjusting driving style.

[cRiPpLe_rOoStEr]

These rearview mirrors look bigger than the ones which were used in the ones available back here. I'd suggest you to replace'em with the ones used in a sports motorcycle to reduce the drag at the best.