[Chrysler300] Re: Auto Choke

[jlsavard@xxxxxxx]

In a message dated 9/6/2004 8:59:14 PM Eastern Standard Time, Woomerj  writes:

Thanks very much for the help. You have me going in the right  direction. I 
have two more questions.
          1. Is there a  vacum port inside the carb that helps to suck the 
hot air thru the tube that  loops down thru the manifold, or does the hot air 
come up thru the tube  naturally because hot air rises?



Jim,
The path of the heated air from the exhaust manifold is into the choke  
housing where it warms the bi-metallic choke coil, then to the "Choke-pull-off  
piston", then down through the main body and the throttle body to a port BELOW  
the throttle plate.  Therefore, it sees manifold vacuum at all times.
 
During the periods of time when the throttle is open (Road load and Wide  
Open Throttle (WOT)), airflow through the carburetor throttle body tends to  
"Blow" the choke blade open against the force of the bi-metallic choke coil and  
the engine receives a richer-than normal mixture to keep running when the 
engine  is cold.
 
When the engine is idling, there is not enough airflow around the throttle  
plate to keep the choke plate open.  That is when the manifold vacuum is  
highest, and it is applied against the choke pull-off piston, which prevents the  
choke plate from closing completely and flooding the engine, which would cause  
it to stall.
 
There is one more choke control mechanism.  That is the "Choke  Unloader".  
If an engine floods when cold, there must be a way to open or  "Unload" the 
choke so as to clear the engine while cranking.  This is  accomplished by a 
portion of the leverage that pushes the choke plate partly  open when you open the 
throttle all the way.  Thus the instructions when  you flood the engine to 
"Hold the throttle wide open without pumping and crank  the engine over".
 
In the wide open throttle position at cranking speeds there is not enough  
airflow to make the main system flow fuel, and the throttle plate is too far  
away from the idle ports to make them flow fuel.  With the choke held open  you 
will soon clear the engine of unburnt fuel.
 
Question # 2.
 I rotated the bakelite housing until the choke just closed. The  indicator 
on the movable bakelite housing was at about 2:00 o'clock and would  only go 
slightly more. It was way past, to the right,of the indicating  lines on the 
stationery bakelite housing. Does that indicate the coil was put  into the 
housing incorrectly?
 
These cabs  were just rebuilt and they may have made a mistake when they put 
them  together.
 
Jim, if you remove the black choke coil housings you will note that  the 
coils are simply slipped into the end of a slotted shaft.  They  frequently fall 
out after they have seen some service.  If you think about  it, you could 
install them in four different ways, depending upon whether you  either rotate the 
housing 180 degrees you could put them in two ways, and/or  "Flop" the coils 
over, two choices, again. 
 
 What to do?  Look at the end of the coil.  It has a 90  degree hook on the 
end.  The coil must be put in so that the hook will PULL  the actuating lever 
on the choke lever arm to close the choke. 
 
Next decision: Put the coil into the housing so it will PULL the choke  
closed. (It is not necessary to put the three screws in just yet.)  With the 
throttle held PARTLY open so that the fast-idle cam is not in the  way, and the 
choke plate is free, put the housing in place and slowly turn  it so as to close 
the choke. (Sometimes it might make things easier to  slightly file the O.D. of 
the bakelite to make it easier to turn.)  Rap the  carburetor so as to 
overcome friction. When the choke is closed, you SHOULD be  about in the middle of 
the adjustment.  If you are not, remove the choke  coil housing and remove the 
coil, replacing it 180 degrees from where it  was.  The scale should be OK, 
then.
 
Something else to remember:  These things have been out in the field  for 
over 40 years.  It is very possible that the bimetallic coils have been  replaced 
by other than standard parts. (They came in different strengths.)   The 
primary thing to remember is that the basic setting is usually "One notch  richer 
than it takes to close the choke plate completely at room  temperature."  All 
else is mostly cosmetic.
 
Good Luck!  These are simple mechanisms once you understand  them.  Let us 
know how you do, and don't be afraid to ask more  questions.
 
Anddddddddd, the Mighty Chrysler lives again.  I transplanted the  wedge 
engine into the '57 with a rebuild, and the transmission acts just like a  new one.
 
Thanks again, 
Joe
 
 
 
 



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