Can anyone explain to me better than the Haynes Destruction Manual that how the choke works and should work properly on the Holy 1920 (no CAP)carburettor, its the tiniest, simpliest little cute thing of a carb I've ever seen on a car, but I don't get the logic behind how the the vacuum diaphragm closes the choke valve...

Scratchin my head...

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Signet '68 4dr, 460k miles and still rollin'

...that's because the vacuum diaphragm (choke pull-off) opens the choke flap slightly, so that the motor doesn't load up on fuel once it has started cold. The choke thermostat (in the exhaust manifold) is what closes the choke. Hope this helps.

D/W

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If it ain't broke, fix it!

Here is how you can test it. crank up the engine when it is cold and disengage the fast idle cam by tapping the gas pedal. With the air cleaner lid off, watch the ckoke blade when you hit the throttle. It should open slightly and then fall back into place as soon as the engine returns to idle. Amazes me how they managed to think up all of these little gadgets and make them work.

1920's are pretty compact. But 1945's are fat and ugly.
Does anybody know exaclty how many cfm a 1945 flows, and is it the highest flowing 1-barrel out there.

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82 D150-225/727
02 Dakota-3.9/5 speed
87 GMC C7000-8.2 Detroit Diesel/5+2

What you are seeing is the choke flap opening due to the low pressure created below it by opening the throttle and the in-rush of air. This is not the choke pull-off functioning. The choke pull-off is what keeps the choke cracked open slightly at idle and high vacuum. The arm and link should pull in with the engine running at idle. I simply compress the linkage and cover the nipple where the hose goes with my finger to check them. If it springs back, it is bad. If it stays "collapsed" until I remove my finger, it is good.

D/W

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If it ain't broke, fix it!

Could this be why my car trys to stall (loud popping noise from the exhaust) as soon as it comes off the choke?

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82 D150-225/727
02 Dakota-3.9/5 speed
87 GMC C7000-8.2 Detroit Diesel/5+2

I doubt it. That sounds like a plug.

D/W

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If it ain't broke, fix it!

Here is some additional info. on choke adjusting. The Carter BBS is shown but the same process can be used on the Holley.
http://www.slantsix.org/articles/choke- ... adjust.htm

You need to be sure the choke thermostat (stove) shuts the choke flap lightly when the engine is cold before start-up.

The choke pull-off needs to open the choke flap when the engine starts.

The linkage pieces will set the richness and the fast idle speeds via the stair-step cam and fast idle screw.
DD