First off,

to LMB
Hello, This is my first post here.
My dad and I recently picked up a 72 Bus (Westfalia, if that narrows it down at all). My dad's pretty good with Volkswagens, but this is the Porsche 914 engine, which is different, he has told me.
Just as a point of clarification, Porsche modified the VW design for the 914. Therefore, Porsches actually have Veedub engines.
The wheels turned freely in all gears, even reverse. What could cause this problem?
I'm not the best with this sort of questions, but my guess would be that the throw out bearing, clutch fork, or pressure plate is not engaging. Or you could simply be stuck in neutral.
We jacked up the back tires, put it in fourth gear, and turned the wheels. The previous owner said the engine "seized up" and didn't explain it any more, so we wanted to see if the engine was busted badly or not so badly.
To check the engine use a 22mm or a crescent wrench on the alternator pulley nut. (this is the recommended way to rotate the engine).
Also, if there's any advice you have for someone who will more than likely have to fix everything, I am all ears. I'm not interested in keeping it stock (not that there's much left to keep stock), so if there's any after market products that will help with functionality or gas mileage, I want to know.
The best thing you can to do is keep up on the maintenance. The only add on that I would suggest is a SVDA (single vacuum dual advance) distributor, if you have a 009 or mechanical advance distributor. Read why here:
http://www.lovemybus.com/forum/vw-bus-repair-questions/do-your-bus-a-favor-ditch-that-009/0/
Also, I want to know what sort of modifications I can be in the market for. The van will be mine once it's running, and I want to make it the best I can. I've heard that turbines and chargers can aid fuel economy, but I don't know anything about either of those and most websites are a bit over my head.
Generally turbo's and super chargers are bad ideas on these engines. They add extra heat and stress to a vehicle already prone to overheating.
If you have plenty of spare dough, then order a rebuild kit from Jake Raby at Aircooled Technologies. They will run over $4,000, but you wont need to rebuild the engine again. plus it's the only complete kit on the market.
Also, nobody on here will give you flak if you call it a van, but other websites will. Most refer to it as a bus.
And if anyone knows of any place I can learn about using any sort of thermal energy produce by the car, I would also like to hear about that.
Use thermal energy for what? Currently the thermal energy wasted going out the exhaust is used to produce the hot air that heats the vehicle, but other than that I am not sure there is much more you can do with it...besides cooking (youtube barefoot chef)

I hope you get the bus back on the road and have loads of fun in it.
