Model Forum / General / Models / October 2007

Not a big fan of the Mopar, but can clue you in on old Fords.

They used a steel tube going from the manifold, to the choke.
As the gas heated the spring, the idle speed cam would
drop, slowing the idle rpm. What wasn't obvious, was
that the spring also moved a small piston in the choke
housing itself, which cut off that flow of hot exhaust gas
that was ported to the butterflys, gas that heated the
area on Autolite carbs to prevent icing and help
atomize the cold gas.

This was in addition to the small exhaust crossover in the
intake  manifold that would warm the bottom intake plenum area.

If all was adjusted right, would give faster pulloff than
manifold coil that Chevys used, or hotwater types.
Downside was it the motor ran really rich, would
soot up, then do a rotten job at pulling the choke
off in a reasonable time.

Now some mopars used a heat riser, that would valve the flow
of gas to the intake crossover, and out the other manifold.
that big crossover would also heat the choke spring, so
would pull off much faster than the Chevy, maybe a little
quicker than the Ford. Bad thing was, those risers would
stick, and really mess things up, like choke coming off
_very_ slow if stuck open, and if closed, would always
route exhaust gas to the crossover and not out the manifold,
and engine would run poorly, and overheat even.

Many guys used to wire them open, or removed altogether
if headers were on, and live with a cold blooded engine.

For the other tube, were you talking about the larger preheat
hose that went to the aircleaner? That heated air also helped
with preventing bogging in the cold

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mike
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