Where to start....
He's saying a lot of stuff. I don't think he's saying that VWs are inherently unreliable. He *is* saying that you can't get one HP per cubic inch from an unboosted internal combustion engine at an rpm reasonably usable by a prop (meaning under ~3500 rpm).
So, when you see an advertisement claiming that a 100 cubic inch engine is good for 100 HP at 3000 rpm, run away. It has nothing to do with being a VW; it's just physics.
There's a lot more embedded in that blog post that isn't explicitly stated. For instance, you can build a much higher displacement VW type engine and make a lot more HP, but you then need a bigger prop, which will likely mean that the main bearing on the prop end will be unable to handle the bending loads & you may break the crank; often at the 1st crank throw inside the engine. To see why, look at the difference between a typical a/c engine front main bearing and the PTO-end bearing of an engine designed to handle only torque loads on the crank (no bending loads). The a/c engine (and engines designed to handle pulley loads to drive accessories, like generators, lawn tractors, etc) will have a PTO-end main bearing that's at least twice as long as a more typical main bearing. VW and Corvair conversion enthusiasts have been adding a '5th main bearing' to their direct drive engines for a while now to mimic that long bearing found in a/c engines.
Hope that helps...
Charlie
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