Kevin,
The original design had coolant running (from the top of the thermostat
housing) through a conduit in the inlet manifold. The idea was to heat the
incoming air, to reduce the need for the choke. This never really made much
sense to me, as you only need the choke when the engine is cold, when the
manifold heater won't do any heating; once the manifold has heated up from
this coolant conduit, the engine is hot and you don't need the choke anyway.
Moreover, hot air is less dense, so if you suck a given amount of hot air into
your engine you are sucking in fewer molecules, so you have less power - this
is why turbo- and super-charged engines use intercoolers, to cool the air
before it enters the engine. The whole thing seems daft to me, but I have
never got around to seeing what happens if I bypass the manifold coolant pipe.
It sounds like your PO has tried what I wanted to try (or maybe just broke the
pipe connectors by accident and decided it was easier to bypass than fit a new
manifold). If your engine runs OK, I would leave well alone - unless you are
concerned with originality, or making it look nice and tidy.
Richard & Daffy
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