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Old 11-06-2008, 10:29 PM   #1 (permalink)
Kalanco
EcoModding Lurker
 
Join Date: Sep 2008
Location: Idaho
Posts: 5

Dragon Wagon - '86 GMC Vandura G25
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Large GMC Van, possible improvements?

I've been reading this forum for a while, and thinking about how I can help possibly restore some life into my van. It's about the antithesis of fuel economy:
'86 Vandura, so it's huge, heavy, and has a large engine in it, the 5.0L 305. That said, I've been thinking of a few things to help it. First off, I know the engine needs work, but on top of that, it was one of the few with a carb, but also a knock sensor/prevention system, so I could relativly safely amp up the compression ratio with a thinner gasket(although it already runs at a 9.5 ratio). Ideally, I would convert it to fuel injection once I get the time and money, but a gasket would help no matter what else I did to it.

Being rather poor, I've just thrown on some duct tape on the grille, which hasn't really affected the tempature at all; once it gets to about the 1/4th point, it stays there under all but the hardest driving. Getting it to the half point, and it cools back to the quarter within about 2-5 minutes.

I do have slightly larger tires(235/75/R15, as opposed to the stock 225's), which should help somewhat(and also seems to make my odometer and speedometer spot on, most of them are 2-3% fast).

The last thing that's caught my eye, is one of these: Gear Vendors Under/Overdrive Chevrolet/GMC Final Drive Ratios.


I don't know if any of you have seen them before, but it seems you can bolt on a 2 speed onto the back of some common 2-4 speed gearboxes(sorry, front engine, rear wheel drive only). I read about a Hot Rod magazine test involving one of these, it increased the FE by about 1-3 mpg, while also allowing one to stay in the powerband easily. Bolt one of those onto my van, with the stock 4 speed, means I have a total of 8 gears to play with.

Can anybody think about other possible reasonable mods I could do? I have some mechanical ability, more electrical ability, but no real fabricating knowledge, and very little money.


As for current fuel economy, I haven't really had the time or ability to test that properly(I was getting roughly 15mpg on the highway, but I was also extremely loaded down with moving things), and the stock mpg is listed as 18 on the highway, 14 or 15 on the city. I'm shooting for about 25hwy, although the lower 20's would be acceptable by the time I'm done with it, and at least 18 in the city, although I'd live with 17.(fun fact, I have a 33 gallon tank. At 25mpg, that's 750 miles on one tank, with 3 gallons reserve).

To my credit, I do also try to do some hypermiling actions(following trucks and/or a bit too closely), shifting into neutral when coasting, I even installed an aftermarket tach so I can keep better watch of my RPM's, which was probably my best add-on thus far.

One thing, just to cut down on the inevitable "trade it in" camp. I love this van. I got it in a decrepit state and barely alive to smooth and strong again. It was literally sitting around, exposed to the elements for 3 odd years, the battery drained, the tires flat, the engine extremely out of tune, and I brought it back to performing excellently. I've driven it from Missouri to Michigan to Idaho, with all of my stuff in it in. I love it, and I don't ever plan on replacing it or selling it. I will drive it till it's doors fall off, put them back on, and drive it some more. The engine has only 94,000 miles on it(the 100,000 mile odometer limit has never been reached), so it has a LOT of life in it still, any mod over the life off it will help, and I plan on driving it for a very very long time still.

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