JMLBlues@aol.com wrote:

My two cents on the plugs up cooling thing -- I don't think one can
generalize about the hottest part of the engine shouldn't be the highest, or
any other such "rule." With engine design (as in most of life) the devil is
in the details. A steam pocket may form regardless of an engine's orientation
if there is an opportunity for stagnation. This is where good test and
development engineering come into play. Most every piston engine runs with
the hottest part of the cooling system high up (the cyl head), and Audi and
VW Rabbits used to have low mounted thermostats and waterpumps. That being
said, the 13B was developed around a conventional mounting, so plugs up won't
have the benefit of problem identification and resolution processes that
Mazda undoubtedly undertook. Personally, I'd be more concerned about the oil
draining. One way to assess this would be to mount accelerometers on the
engine to sense increased vibration from rotor imbalance due to accumulated
oil. The results could be judged qualitatively by comparison, or someone with
a lot more time might be able to calculate the imbalance from the vibration
amplitudes. Not a simple task.

Jon

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