Looking at getting into the baja seen with a kombi. how many km do you guys get to a tank with an air cooled engine. Also how many km with modified non vw 's. Wont be going as big as 33's, maybe 29's.

cool

I ran 31's with a 1600 kombi box and 2L type 4.......

Usually got about 350klms out of a tank when we were loaded up on a trip away

That's not too bad. My last kombi was a 1600 tp with stock wheels and was lucky to get 400km.

I used to get about 400km / tank from a very sick 1800 type4 dual carb with a 1600 box. Stockish wheel / tyre sizes.
Generally you'll probably get 350 - 400km a tank no matter what with a VW engine. Non - VW engines it's totally arbitrary. The vehicle they came out of can give a rough idea of economy within reason. Not just car X got Y km/L, but such factors as the mass of the donor, transmission ratios and wind resistance.

Don't underestimate the last one. Sure the vans are pretty un-aerodynamic, but they can be made a whole lot worse. Addition of bullbar, spare tyre, driving lights, mesh protectors etc all impact.
In an era long ago, when I was experimenting with using and not using the mesh windscreen shield the difference was unbelievable. With it on the van struggled to get past 80km/h.

If you are using a 1600 box on something bigger than a 1600 you'll find yourself running out of gears awfully fast in normal road driving unless you have big wheels.

1600 box, 31" tyres, 1800 turbo/fuel injection - round about the 400km mark aswell.
think about how many km you plan on doing, if you don't use it too often it doesn't really matter. I did a mass amount of km in mine and i cried for the fuel economy that a subi can bring.

You guys are quoting around the same as I've been getting from my 1800 DC with an 1800 gearbox.
What sort of fuel economy do you get in a modern Dual Cab- what would that be: 3.5L V6, nearly two tonnes dry weight. I can't imagine the fuel economy to be any better... Sure it will have better performance and all that, but that just jumps the fuel usage too...

Same with the buses, a new Tarago doesn't get fuel economy any better than my 8 seater 79 with a reco'ed 2L engine.

Anyway, I am looking to replace the the 1800 gearbox for a 1600 and big wheels. Using Excel I've found that the 1600 box with 30" wheels is the same as the 1800 box with standard wheels. So it should have the same fuel economy. But look cooler and handle mud and dirt tracks down to the river better.