is make choke plate open enough - 69 chrysler 300

[gransedan]

Hi there,

When the engine / intake is warmed up the choke plate is open like in this picture.
Should it open more? If so, what could I do about it?
The choke thermostat seems to be in good order, but could pull a little bit down more to open the choke plate a little bit more.
Or should that be adjusted more?

'69 - chrysler 300 with orginal carb.

Thanks for your suggestions, Pieter

 

[Big_John]

If the car is running, then that choke isn't opening all the way. Check the vacuum choke pull-off (that gold piece with the hose attached). Take the hose off, push the pull off in and cover the nipple where the hose was attached with your finger. If releases, it's bad. It should then release as soon as you take your finger off.

If the car isn't running in that pic, then there's no vacuum for the pull-off to fully open, so check it with the engine running.

 

[CBODY67]

The choke plate is offset on its shaft, such that air flow will open it more as engine speed is increased.

Otherwise, the plate should just close at about 65*F ambient (engine/carb and air around them). Then the choke pull-off will open things from there and then the thermostat takes over after that to further open the plate to vertical.

Is is common for choke thermostats to tighten with age. The ARE adjustable. First to get the hold-down bolts out of the intake manifold without snapping them off! Take a hammer and tap the bolts first, then soak with penetrating oil, and tap again.

I would try going one notch/line leaner than the current setting. Then re-check when things are cooler again. Engine/carb and air around them. Usually one notch leaner has worked for me.

Just some thoughts and experiences,
CBODY67

 

[gransedan]

If the car is running, then that choke isn't opening all the way. Check the vacuum choke pull-off (that gold piece with the hose attached). Take the hose off, push the pull off in and cover the nipple where the hose was attached with your finger. If releases, it's bad. It should then release as soon as you take your finger off.

If the car isn't running in that pic, then there's no vacuum for the pull-off to fully open, so check it with the engine running.

car is running

If the car is running, then that choke isn't opening all the way. Check the vacuum choke pull-off (that gold piece with the hose attached). Take the hose off, push the pull off in and cover the nipple where the hose was attached with your finger. If releases, it's bad. It should then release as soon as you take your finger off.

If the car isn't running in that pic, then there's no vacuum for the pull-off to fully open, so check it with the engine running.

this is with running engine, choke pull-off works. Is the choke plate open enough you think?

 

[CBODY67]

Thanks for the additional information.

Download the FSM at www.mymoper.com (might have to manually input that address) and read the section on choke adjustment for your Holley 4bbl. Free download.

CBODY67

 

[Big_John]

car is running

this is with running engine, choke pull-off works. Is the choke plate open enough you think?

View attachment 722536

If the engine is up to operating temperature, it's not open far enough.

The best thing to do is get yourself a factory service manual and go through the choke adjustment procedure word for word. That will get you to a good baseline and then maybe you'll want to tweak it a little.

 

[Big_John]

Thanks for the additional information.

Download the FSM at www.mymoper.com (might have to manually input that address) and read the section on choke adjustment for your Holley 4bbl. Free download.

CBODY67

That was my first thought too, but no '69 Chrysler there (I just looked before I posted the above LOL) Service Manuals – MyMopar

There is a '69 Dodge and '69 Plymouth and those may do it, but a correct FSM, is always the best.

I can't help but wonder why you can't post a complete link.

 

[68PK21 440.6bbl]

He needs to find the numbers on the Holley carburetor to see if it is really the 'original' carburetor as over the cars lifetime out of his control it could of had a 'this will work' aftermarket rebuild carburetor replacement.

All my service manuals show the 4160 Series Holley carburetor's whether Chrysler, Dodge or Plymouth.
Then again you have what kind of pollution control class the car was manufactured for.

1968 Plymouth Service Manual shows Holley 4160 Series 4bbl

1969 Plymouth Service Manual shows Holley 4160 Series 4bbl

1970 Chrysler Service Manual shows Holley 4160 Series 4bbl

1970 Monaco/Polara Service Manual shows Holley 4160 Series 4bbl

Holley has it's own manuals for individual series/models and is good reference for mongrel carbs.

.

 

[Toolmanmike]

car is running

this is with running engine, choke pull-off works. Is the choke plate open enough you think?

View attachment 722536

The vacuum pull off is a primary pull off and works as soon as the engine fires to crack the choke open to prevent flooding. The thermostatic coil in the intake opens the choke as the engine builds heat. If your engine is up to operating temperature and the choke is still partially closed as in your photo, you may have to bend the choke rod a bit. (the long rod right in the middle of the photo) That's an old crusty carb and linkage. A good soaking with carb spray may help a bit.

 

[CBODY67]

From my experiences, Chrysler did not use one carburetor specific to any one carline, with the same engine/transmission/emissions calibration package. It was the same Holley part number carburetor for all of the carlines.

As to the choke operation and such, that would be common to all Holley 4160 and 4150 4bbls. The 4150s had a metering block for the primary AND secondary sides of the carb. The 4160s have a metering PLATE for the secondaries instead. Usually the HO Chevrolet engines (302 Z/28s, 427 L88s, etc.) had 4150s, in this time frame.

So for THIS purpose, any carline factory service manual will do, from my experiences and observations.

Additionally, just because the engine coolant temp indicator indicates the engine is "up to operating temperature" does NOT mean that all sections of the engine are that hot. Including the heat crossover passage under the carb, where the choke gets its heat from. IF that passage is more than 1/2 clogged with carbon and "stuff", the choke thermostat will see less heat than one where the passage is totally clean and with the heat riser valve operating as designed. As in not "frozen" 1/2 closed as can happen in many cases. So, then the choke can only rely on heat migration into the intake manifold area for its heat, which can take much longer to happen than just the coolant getting hot. Eben worse if the heat crossover passage has been blocked with a plate for allegedly better performance or whatever.

Enjoy!
CBODY67

 

[gransedan]

THANKS, enough info to work with. MUCH appreciated

 

[CBODY67]

As an additional note, I was talking about Chrysler-spec carburetors with divorced choke systems. GM-spec Holleys had similar systems, even some with internal choke thermostats, as Ford Holleys had internal choke systems, but sometimes used a heater hose running beside the thermostats to get heat to the thermostat quicker. Of course the later electric choke models all had internal choke systems.

Just some clarifications,
CBODY67