hot air comp.

[Toronado]

on the back of my carb. theres a metal tab
with a push in pin with spring i think its
called my hot idle compensator under the metal
tap there a o-ring and a bi-metal piece. Can I plug
this hole, or just leave it open? What is the point of it,
i never see it on any other carbs? I was told it
gives the carb. extra air when it gets hot?

[Schurkey]

Yup.  Not all carbs have the drilled passages, but it's often obvious where the machining operations would have been done.

Engine begins to overheat, added air may raise the idle speed and allow the fan and water pump to spin faster.  Added air kinda offsets the fuel vapors boiling out of the carb bowl.

[Toronado]

I will push in the pin and
see if it raises the RPM's then
I will know if the bi-metal (heat reactive) is still working.
I think last time i pushed it in while normal
engine temp. it made it sound bad?

[Cliff Ruggles]

I block off those by melting lead into the hole and smashing it out with a small round punch.

The only time one may want to use HIC, is on a vehicle that is daily driven, in hot weather, and has to sit in traffic well heat soaked, with the A/C on, etc.

Rochester used HIC on some early models, then it dissappeared in the later years.  Guess they figured it didn't work all that well either.....Cliff

[Toronado]

Yet again Cliff you made my day.
not only do you have great insight
you seem to know the design progression
for Q-jets like no other. I now remember
some literature talking about A/C and the
hot air compensator, & i have removed
my compressor and the condenser so
time to eliminate the carbs A/C heat hole LOL . I'll cut a
extra carb gasket to size & use under the plate,
 that will seal it.