Dave,
When the smog pump was added, the alternator
was moved over to the lower left side of the
engine. Since the new mounting location placed
the pulley closer to the front, and different
crank pulley was used.
To space out the water pump to match, Datsun
used a spacer, about an inch thick.
Fan Clutch was used on the emission '68-'70
1600 & 2000's.
Side note on the emission, in those years it was
only checked at idle. Hence the 0 BTDC ignition
timing, air pump, and RICHER needles to help promote
burning of the remaining A/F mixture in the exhaust
manifold. Higher engine temp, as higher under hood
temperature resulted.
Alas, many of the emission components that were
added were not that reliable. It was not uncommon
for the carbon vanes in the air injection pumps to
fail. Pieces of carbon would jam the "gulp" or anti
backfire valve, leading to a lean condition.
The wax pellet used on the fan clutches also would fail,
leaving the fan to freewheel. The seven bladed fan was
designed to pull in lots of air at idle, but once up to
speed (above 20 mph) there wasn't much use for the fan,
especially one with such a high drag, so the fan clutch
was designed to disengage once it was cooler.
On the U20's, they were borderline on the engine heat.
So a "thermal modulator" was added to apply full vacuum
to the distributor when the engine got too hot. They worked
fine, yet tended to fail early on.
Sigh, all of these added up to some old time mechanics
commenting "those darn aluminum cylinder heads just plain
warp, and are no good!".
Cheers,
Tom Walter
P.S. Missed the TDROC spring fling this weekend. Way too
much to get done. Darn. "All work, and no play.... " ;-(
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