Choke/carburater: Manual Vs Automatic / Differences

[pflaming]

My 53 Plymouth has an automatic choke; my 52 Dodge truck, a manual choke. 1. Are the two carburators the same? 2. Is the choke between the carb and the manifold? 3. How many additional 'parts' are required on an automatic choke. 4. Was it an improvement aside from being a 'comfort' device. A manual choke is only used for a few minutes and for me is a nice ritual, so (5) does an automatic choke provide a benefit beyond assisting in starting the engine?

[desoto1939]

Are you refer to the Sisson Automatic choke that bolts to the top of the manifold?

 

This is an electromagnetic choke.  On my 39 Desoto the starter switch which is the old style push button on the floor board. This hits a bronze or cooper  plate. There is a wire that screws in to the starter switch and this wire runs to the sisson choke. When the contact is made the electrical contact then forces the choke to close and the choke is now on in the carb the butterfly is closed. The engine will run at a higher rpm untilo the heat from the manifold warms up the bimetal plate that is under the choke.  There is a gasket the goes between the sisson choke body and the manifold.

 

When the enine has warmed up then the choke slowly opens up and the engine runs a normal rpm.

 

Also note that the automatic choke will always engage when ever you start the engine even in hot weather.

 

There are two major style of the sisson choke and after 1949 the ply used the choke that sits infront of the carb.  These chokes are now going for over $250 each.

 

So a manual choke is controlled by you when ever need and costs a lot less.  I have pictures of these and also a power point presentation that I did at the AACA annual meeting this past winter.  Let me know your home email and I will try to send it to you.  The PP might also be in the Tech section on the forum but not sure if it was added or not.

 

Rich Hartung

Desoto1939@aol.com

cell 484-431-8157  phila pa. 

[DJ194950]

My 53 Plymouth has an automatic choke; my 52 Dodge truck, a manual choke. 1. Are the two carburators the same? 2. Is the choke between the carb and the manifold? 3. How many additional 'parts' are required on an automatic choke. 4. Was it an improvement aside from being a 'comfort' device. A manual choke is only used for a few minutes and for me is a nice ritual, so (5) does an automatic choke provide a benefit beyond assisting in starting the engine?

No,

the choke linkages on the carb are differant and hard to try to make an auto choke carb. work good with a mechanical choke(would not stay closed or would not geta full choke I tried being cheap!). Found several reasonable priced used auto chokes on Ebay in the past years. Seems everything now has gone way up on Ebay lately!.

Here in central Ca. chokes are never a necessity, pump carb. several times and hold a higher rpm until slightly warm (or pull choke to activate the rpm step up linkages to hold an higher rpm for warm up.

The auto choke does the same thing at cranking by closing the choke fully (if it's cold enough to tighten the spring in the choke mech.) and drops back to approx. 75% choke after cranking then drops off when exhaust manifold warms up (again throttle must be stepped on to release high idle lingage at carb.

 

Just a nice addition in my opinion, but not really necessary. Post war sales points!

 

When you get the Vert running if choke doesn't work, first check adjustments as they are really solid if adjustments are followed.

If not working as I believe I have a Spare later syle that we could deal on.

 

Best to ya,

 

Doug (Modesto)