I tend to lurk in the background here and learning lots, but I will throw in my two bits on this
subject.  First, our dear old air-cooled VW all had gear-driven cam shafts.  And so did the early
Porsches.  I don't know about the Porsche flat 6's - out of my price range and experience.  I'm
not a mechanical engineer, but I have read some about engines, like many of here, and it would
seem that there are many factors, potentially more significantly, that affect low-end torque more
than timing belts vs. chains such as displacement, crank throw, connecting rod length, valve
timing, compression ratio, etc.  I've only replaced one timing chain (Alfa Romeo) so I can't speak
to the comparative difficulty of replacement.  In the cobwebs of my memory, I have a dim
recollection of reading about the comparison of chains vs. toothed belts for bike transmissions.
I think the chain was slightly more efficient; however a toothed belt could be a better choice for
a single-speed - low maintenance, self-cleaning, water-resistant.  Good for a kid's bike, no?

Where are the Fun Phrydaye subjects?

Rob
a.k.a. Oldkayaker
1987 Wolfsburg Weekender Vanagon