Holley Electric Choke Question

[mopowers]

How important is the vacuum signal for the electric choke on a Holley carb? I've noticed Proform and other Holley-type carbs do not have a connection to vacuum.

Is it to cool the bimetal coil in the choke housing?

 

[mopowers]

Also, does anyone know what this piston does (circled below)?

 

[toolmanmike]

Primary pull off? Just guessing.

 

[krazykuda]

Also, does anyone know what this piston does (circled below)?

View attachment 1715231518

That piston moves up and down...

 

[diymirage]

That piston moves up and down...

not necessarily, you can clock it so it moves sideways

 

[mopowers]

not necessarily, you can clock it so it moves sideways

Actually, you can't. It's part of the housing that's affixed to the carburetor.

I believe the piston meters the vacuum signal. When the engine is cold, the piston is up, not allowing vacuum to flow. When the thermostatic choke coil heats up, the piston moves down allowing vacuum and subsequent air movement to help cool the coil and keep it from overheating. That is my theory anyway.

Does anyone know for sure?

My question still remains though- How important is the air flow from that vacuum source if some electric choke housings have it, and some don't?

 

[diymirage]

Actually, you can't. It's part of the housing that's affixed to the carburetor.

just clock the carb, junior