The Porsche 911 air-cooled engine doesn't make sense on paper. It's mounted behind the rear axle, which means the weight distribution is completely wrong. It's cooled by air, which means the thermals are more complex than a water-cooled engine. The crankcase is magnesium, which is wonderful until it's corroded.

And yet it's one of the most beloved engines ever built. It revs to numbers that embarrass modern pushrod engines. The sound is distinctive and addictive. The driving experience it enables — rear-engine, rear-traction, that unique weight transfer characteristic — is unlike anything else.

Restoring one is expensive and detailed work. Every time I've done it, I've come away understanding why people pay what they pay.