1970 Chrysler Newport Cater BBD choke question

NWPT70

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Hi,

Now that the sub freezing temperature is finally here I was able to give my 70 Newport a true old start cold start. Two pumps of the gas pedal, hit the key, and it cranks to life quickly- however I noticed that for the first minute and a half of warm up, the exhaust is very rich (smoky) and the engine really burbles and is a bit shaky. The engine speed will pick up, smooth out and reach high idle after about 2 -2.5 minutes. At that point I can then tap the gas and the idle drops to a smooth healthy idle. My question is, can the choke be adjusted to not be set so rich? This carburetor was rebuilt over the summer and I never recall warmups having such a rich condition for the first minute and a half. Normally just fire up and go right to high idle. Any thoughts?
 

413

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Yes it’s adjustable, check the choke pull off. It’s the vacuum pod connected to the choke. When car cold starts it should open the choke About 1/3 of the way. They can go bad and not open it at all.
 

CBODY67

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The FSM details how and WHERE to adjust the choke pull-off link. You can manually check it with the engine off and full-cold. Also, with age, the choke thermostat can tighten up, delaying full response to heat. Effectively making it have a richer setting than it should.

In the mean time, tweak the pull-off link adjustment with a wide flat-blade screwdriver a bit to possibly open that initial setting a bit more. When Spring is in bloom and ambient temps are in the 70 degree range, THEN check the adjustment of the thermostatic choke coil. At 70 degrees F ambient on a cold, unstated engine, the choke plate should just close. Not a firm "snap" close, just an easy close. Reset the choke coil leaner to accomplish that, if necessary. Possibly, you might need to close-up the pull-off link adjustment, but it might work just fine, too. One of those "cut and try" tweaks, from my experiences.

On any older vehicle, stock service manual specs should be the starting point in fine-tuning automatic choke actions. NOT the end point, even with new parts. Just my experiences. Get things to work right with how you use them, if that might differ from the factory starring procedure recommendations. Recommendations and specs done when "gasoline was real" and not E10 or so.

What weight of motor oil and how recent is the tune-up? Just curious.

From my experiences,
CBODY67
 
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