Choke driving me crazy!

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71DartNY

71DartNY

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Jun 23, 2017
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Putnam County, NY
Hello, new member but have been lurking for a few years since I got my Dart.

I’m having trouble adjusting the divorced choke on my 71 Dart. I can’t seem to get enough range out of it. If I adjust it so that its closed when the engine is cold, it won’t fully open when the engine is hot. If I adjusted it so that the choke is fully open when the engine is hot, then when the engine is cold, the choke is only half to ¾ closed. I’ve bent the choke rod back and forth to shorten and lengthen it, and have also turned the little screw that turns the spring on the choke back and forth, but can’t seem to get it dialed in.

The best I can seem to accomplish is having the choke adjusted so that its fully closed when cold, so that the engine starts easily, but when hot, the choke is like 80% open and the fast-idle screw is still resting on the fast-idle cam.

Last night I had adjusted the choke so that when the engine was hot, it was fully open and I thought I had it diad in, but when I tested it out this morning, (72 degree ambient temperature) pushing down the throttle only caused the choke to be about 3/4 ‘s of the way closed. Maybe it’s too warm outside for the choke to be fully closed? I don’t know, but any help would be appreciated.

  • Ambient temperature has been between 70-80 degrees while making adjustments.

  • Carburetor is a carter BBD 4958s and was completely rebuilt 2 weeks ago, by me.

  • 1971 Dodge Dart Swinger (all stock) 318V8 3spd a904

  • Runs great, otherwise. No sputters, stumbles or drivability issues. Idles great.
 
That's why I prefer to change over to 4 bbl with electric choke... They are much more reliable than the choke thermostats that came stock...
 
What are the chances that the choke element is worn out?
Are you aware that there is a heat crossover system underneath the carb? And how it works? In conjunction with the heat-riser valve?
Do you have a choke timer bolted to the intake?
 
krazykuda said:
That's why I prefer to change over to 4 bbl with electric choke... They are much more reliable than the choke thermostats that came stock...
Click to expand...

I'd like to keep this setup stock for the time being. I've got a big block setup waiting to be rebuilt so I really don't want to spend too much money on the current setup. I just want it running well so I can enjoy it until I'm ready to start my big block build in a year or two.
 
AJ/FormS said:
What are the chances that the choke element is worn out?
Are you aware that there is a heat crossover system underneath the carb? And how it works? In conjunction with the heat-riser valve?
Do you have a choke timer bolted to the intake?
Click to expand...
Yes, I would look for a choke coil online. Worth a try for sure. Now days there is no shame in modernizing chokes and ignition systems on these old cars. Most car show judging even allow it unless you are in the absolutely OEM class.
 
toolmanmike said:
Yes, I would look for a choke coil online. Worth a try for sure. Now days there is no shame in modernizing chokes and ignition systems on these old cars. Most car show judging even allow it unless you are in the absolutely OEM class.
Click to expand...
Hang-on, you can check your coil with a hi-powered hot-air heat-gun
 
35495569275_8200193b36_o.jpg
AJ/FormS said:
What are the chances that the choke element is worn out?
Are you aware that there is a heat crossover system underneath the carb? And how it works? In conjunction with the heat-riser valve?
Do you have a choke timer bolted to the intake?
Click to expand...
AJ/FormS said:
What are the chances that the choke element is worn out?
Are you aware that there is a heat crossover system underneath the carb? And how it works? In conjunction with the heat-riser valve?
Do you have a choke timer bolted to the intake?
Click to expand...

I installed a new choke thermostat. Is that what you mean by choke timer? It bolts to the manifold with an arm that attaches to the choke plate. The bi-metallic spring heats up which causes the choke plate to open,

I'm aware that the choke thermostats gets heated up by the intake manifold, but don't know about the heat-riser valve.
 
AJ/FormS said:
Hang-on, you can check your coil with a hi-powered hot-air heat-gun
Click to expand...
Crazy that you mention that. I used to sell (years ago) a compressed air powered tool that would produce heat out of one side and cold out of the other just for checking chokes.
 
AJ/FormS said:
Hang-on, you can check your coil with a hi-powered hot-air heat-gun
Click to expand...

It's brand new. I bought it cause I thought the old one was worn. But seems to work just like the old one did. Whomever had the car before me must have never got it adjusted right either.
 
toolmanmike said:
Crazy that you mention that. I used to sell (years ago) a compressed air powered tool that would produce heat out of one side and cold out of the other just for checking chokes.
Click to expand...

While making adjustments last night. I'd bend the little rod on the choke thermostat in tiny increments at a time. Every time I'd make an adjustment, I'd pull the choke thermostat off the car and pop it in the freezer for 5 minutes so that it would reset itself then put it back on the car. I thought that would save me some time so as not to have to wait until it the spring cooled down and retracted on its own.
 
71DartNY said:
While making adjustments last night. I'd bend the little rod on the choke thermostat in tiny increments at a time. Every time I'd make an adjustment, I'd pull the choke thermostat off the car and pop it in the freezer for 5 minutes so that it would reset itself then put it back on the car. I thought that would save me some time so as not to have to wait until it the spring cooled down and retracted on its own.
Click to expand...
You got the right idea, but since the ambient down there is currently 70/80, now you just have to wait for it to warm up. I just toss in in a pail of water for a few seconds.
But here's the thing, what turns that thing off as the engine warms up?
Well, I'll tell ya,pilgrim........If you had factory log-manifolds, there would be a stainless steel valve in one of them controlled by a clock spring, that looks exactly like that choke spring, except heavier duty. It's job is to restrict the exhaust on that side, forcing some of it to travel up under the carb and over to the other log manifold. Of course this exhaust is about 400*F so it heats up that area around the choke well,in addition to heating up the carb. As it heats up the manifold and thus the choke coil, that coil opens the choke plate.
So if the passage under the carb plugs up with carbon, or the heat-riser spring is missing or the valve itself is seized or MIA, then the choke coil never gets warm enough to fully open the choke valve.

By your picture, this choke coil is not electrically assisted, so, forget I mentioned choke-timer for now.
 
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AJ/FormS said:
You got the right idea, but since the ambient down there is currently 70/80, now you just have to wait for it to warm up. I just toss in in a pail of water for a few seconds.
But here's the thing, what turns that thing off as the engine warms up?
Well, I'll tell ya,pilgrim........If you had factory log-manifolds, there would be a stainless steel valve in one of them controlled by a clock spring, that looks exactly like that choke spring, except heavier duty. It's job is to restrict the exhaust on that side, forcing some of it to travel up under the carb and over to the other log manifold. Of course this exhaust is about 400*F so it heats up that area around the choke well,in addition to heating up the carb. As it heats up the manifold and thus the choke coil, that coil opens the choke plate.
So if the passage under the carb plugs up with carbon, or the heat-riser spring is missing or the valve itself is seized or MIA, then the choke coil never gets warm enough to fully open the choke valve.

By your picture, this choke coil is not electrically assisted, so, forget I mentioned choke-timer for now.
Click to expand...

Thanks! Best explanations I've heard on how the undermanifold portion of the choke system works. How do I test if the heat valve on the exhaust manifold is working?
 
Well, first you have to find it. I think they only started using them in about 68. And I think it was in the drivers side. With a cold engine, you just reach down and see if it turns. There is a big circular counterweight attached to the valve by a pivot-shaft. It must rotate freely, from it's normally closed position to about 90* further which would be wide open. Then there is the clock-spring which should be trying to keep it closed. And on the other side is an anti-rattle spring.
So that's all the parts there are too it, but you still don't know if the valve is on there. Not to worry, I've never seen one missing, although I have not seen that many,lol.
But I gotta tell you, that the most troublesome part of this system is the passage under the carb. It is all too common for it to become clogged with carbon. This carbon is actually formed from the oil that is sneaking by the worn parts of the engine and ending up in the exhaust system. I have removed many intakes to chisel out these passages,on both sides of the gasket; that is to say,also in the heads. This used to be quite common on higher mileage engines.
 
When I put a 73 dual plane intake and 2 brl on my 67 273... same 73 model choke, everything except... I purchased the thickest carb base gasket I could find to put under that 2 brl. , reduce fuel percolation. That is what changed the chokes throw. At one point I thought I might have to fab a spacer to lift the choke from the well 1/8 inch. As I continued with adjustments, creative rod bending and such, I noticed the little vacuum choke pull wasn't fully retracting. It worked to create the primary gap no problem ( set via horse shoe bend in its link ) but without a slight finger assistance it stopped short of its full travel. Replacing that cured it. A slight vacuum leak in it or just worn out? I don't know.
Now I can actually kick the choke out before the engine/choke is fully warmed which is something I hadn't been able to do when this intake and carb was on the 318 in our 73 Valiant.
 
I have made custom choke rods to fit various carbs to my 66 273 Barracuda. I use a similar sized welding rod, grind the set out of a hacksaw blade to cut the C clip notch, do bends in vise.

I reference the choke linkage hole, with choke in closed position, to carb base using caliper. If 3/8" thermal spacer added, then add 3/8" to rod. I found that BBD, Holley 2280, and 71" Rochester 2, all bolt on, but have different choke hole to base measurement. Making new rods for each, made them each work perfectly. The choke bi-spring is set so choke is just set closed at about 68F, above that, not fully set. Also when warmed up, choke should go full open.

After evaluating all carbs, Rocher 2CV, is my favorite.

I forgot to mention there is also a sight variation in the lateral measurement of choke hole, for carbs. The bi-spring adjustment has limitations, keeping operating angle in range, avoids binding, for full operating travel, the #1 reason to make correct length rods.
 
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KitCarlson said:
I have made custom choke rods to fit various carbs to my 66 273 Barracuda. I use a similar sized welding rod, grind the set out of a hacksaw blade to cut the C clip notch, do bends in vise.

I reference the choke linkage hole, with choke in closed position, to carb base using caliper. If 3/8" thermal spacer added, then add 3/8" to rod. I found that BBD, Holley 2280, and 71" Rochester 2, all bolt on, but have different choke hole to base measurement. Making new rods for each, made them each work perfectly. The choke bi-spring is set so choke is just set closed at about 68F, above that, not fully set. Also when warmed up, choke should go full open.

After evaluating all carbs, Rocher 2CV, is my favorite.

I forgot to mention there is also a sight variation in the lateral measurement of choke hole, for carbs. The bi-spring adjustment has limitations, keeping operating angle in range, avoids binding, for full operating travel, the #1 reason to make correct length rods.
Click to expand...


Great info thanks! You answered a very important question for me that I don't think I asked before. 68F is basically the cut off on when the choke should be fully closed. Perhaps the reason why I believe I'm not getting enough range out of the choke is because I'm expecting the choke to be fully closed when the engine is cold, even though ambient temperature has been in the mid 70's to low 80's while making adjustments.
 
There you go!
The cold engine will still want to be enriched at 68, but most of the time this can be overcome in the tune and with a minute or so of babysitting, as I call it; namely keeping the revs up or blipping the throttle.
Since you have a choke (I don't), you can use a little of it to get up on the fast idle cam, and then let her idle for a minute or two, then she might be good to go.
 
Ooooooooo, she's a beauty.

You see that 57 BelAir up top there? My first car was a shoebox 57 just like that except a 4dr hardtop.
My second, the following year, was a 1970 Swinger 340/4-speed, and the rest is history;47 years of Mopars and a high percentage of 4gears. About 30 years worth of M/Ts
 
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68F is for s cold start, just barely full closed for prime after depress of throttle one to set linkage. Start should be immediate, the vacuum on choke pull-off immediately opens choke the proper amount, then the bi-spring open choke, and further movement steps fast idle cam towards normal idle.
Following carb setup instruction in proper order typically works well, insure settings are correct for particular vehicle. Correct settings should not require baby sitting of throttle. The engine, should not stall, nor run stinky rich or chugging.

In mild weather an engine should be warmed in in about 1 mile at 40 mph. I find this is true for modern cars too.
 
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