273 stalling - diagnose?

[70DartMike]

My head is too swamped with stress and school to figure this problem out right now, but I am daily driving the car so I need you guys to diagnose this for me.

The car is a 65 Valiant, engine is a 273, 2bbl, auto tranny. Electronic ignition. Previous owner rebuilt the motor, did the rings and bearings, about 3 years ago.

It's been running great the whole time, and I've done general maintenance on it.

Ok, start it up in the morning, and let it warm up for about 10 - 15 minutes. It immediately goes to a high idle due to automatic choke, and when I kick it down, it runs OK, and then wants to stall. I don't kick it down right away, I give it time to warm up. It's about 3 degrees Celcius in the mornings here.
Once I've been driving for 5 - 10 minutes, the idle is back to normal (somewhat), without stalling issues. It just seems that it's stalling a lot lately where it never used to. It doesn't stall at all in the high idle. Any ideas? If you need more info, I'll gladly give it.

 

[67Dart273]

Could just need a tune up. Are you aware of the choke pull-off and how it works? The choke could be mal -adjusted, or the timing/ idle/ mixture settings could be just on the ragged edge to where it doesn't want to run in the "in between" engine temps

One thing I'd try is getting it warm, adjust the idle screw(s) properly, and then set the idle as high as you can without it creeping excessively in drive.

 

[70DartMike]

Could you go through adjusting the idle screws properly with me? I've never really been sure on those.

And no, I'm not too familiar with the choke pull off.

 

[67Dart273]

Earliest shop manual download I know of "fer free" is for a 66 but that should be close enough to your 65. I suggest you do that first and do some reading:

http://www.forabodiesonly.com/mopar/showthread.php?t=132309&highlight=manual,+download

Here's the direct link for the '66 manual:

http://www.forabodiesonly.com/mopar/showthread.php?t=132309&highlight=manual,+download

Generally, the way the "choke pull off" works is like this:

The engine, shut down, gets cold, the choke thermostat moves, putting pressure against the choke linkage.

When you floor the throttle and let off, this "sets" the choke. Moving the throttle allows the step on the fast idle cam to "clear" and allows the spring pressure of the choke thermostat to close the choke, so when you let off the throttle, the choke is closed, and the fast idle cam is "set."

When you fire the car, the vacuum of the engine, even turning over, may "suck open" the choke some amount, designed into the beast to prevent too much choking.

When the engine starts, an OVER choke situation exists. The CHOKE PULL OFF (sometimes hidden, IE Holley style choke stats) is a vacuum diaphragm or piston that is hooked directly to manifold vacuum

This "pull off" operates on engine vacuum, and opens the choke a TINY PREDETERMINED amount. If it does not work (blown diaphragm, gummed up piston, missing linkage, out of adjustment, whatever.......) then the choke OVER chokes the engine, causing black smoke, puking, sputtering, and dying

In this sideways photo, the pulloff is the little round device on the "top left" of the carb, with the U shaped link wire coming out. This U shape wire is what you bend to adjust the specification. Not visible is a short little vacuum hose that comes out the back and goes into the base of the carb

The shop manual will have a "spec" on how to adjust for your carb

IDLE

FIRST you want to set the ignition points if you have them

SECOND you want to get the timing where you want

THIRD you "rough in" the park/ neutral idle speed and get the engine FULLY to warm operating temp.

FOURTH adjust the idle mixture screws. back them out some, then slowly turn in until you hear the engine drop in RPM, or watch a tach. Adjust them back out until the RPM JUST comes back up. Do this back and forth for both screws, and readjust the idle SPEED if necessary to keep within reason.

IF you have a vacuum gauge, you can go back and forth between the idle mixture screws and adjust them as above, alternately for HIGHEST manifold vacuum

(What you want is highest RPM smooth idle, "leaning" toward the "lean" side, or turning the screws in (cw)

NOW that you have this all done, finally adjust your idle speed, and for an automatic, this means IN GEAR, so block the wheels, set the brake, and if possible, use a second person with their foot on the brake.

The "tuneup" books (and the shop manual) will have specs on idle speed, l but I tend to use that only as a guide. Especially if a car has a different cam/ intake/ carb/ etc etc I tend to set the idle to my own liking. In fact, as I said, I like to set it about as high as I can without excessive forward creep in gear.

On my 67, which now has a 360/ stock converter/ mild cam, the idle is about 900 or 950 in neutral. I ALWAYS kick it into neutral at a light, habit, I guess, from my "stick" days.

 

[65Val]

Mike...I think you have a carburetor icing issue. I know you live in the same climate as me, and I've experienced this symptom for years. I bet it just started happening, since the weather has changed, right?

You need to get some heat to the carb quickly during warm-up. Later engines had a heatstove, transfer pipe and flapper valve, to get warm air to the carb during cold weather drive-away.

 

[70DartMike]

Mike...I think you have a carburetor icing issue. I know you live in the same climate as me, and I've experienced this symptom for years. I bet it just started happening, since the weather has changed, right?

You need to get some heat to the carb during warm-up. Later engines had a heatstove, transfer pipe and flapper valve, to get warm air to the carb during cold weather.

Matter of fact, I've been living at Rob's house (Rob on here) for the past month and a bit while doing my 4th year electrical at Camosun.

I remember Joe doing something like this with his Power Wagon, but he made something up where he wrapped copper piping around the carb.. I'll see if he'll part with it.

 

[65Val]

Mike....Ideally, what you need is to get heat in the intake air stream. That will warm the carb just enough to stop the icing and fuel puddling when cold. Once the engine gets nicely warmed up, the problem disappears. Maybe check with the auto wreckers around these parts....you may be able to adapt the later setup to work with your early exhaust manifold.

A lot of people removed this equipment mistakenly thinking it was part of the emission control system, which it is not.

 

[67Dart273]

A lot of people removed this equipment mistakenly thinking it was part of the emission control system, which it is not.

Actually it IS part of emissions. And his 65 didn't have that originally. Neither did my non California made 67 273.

I agree, though, that if the manifold butterfly is stuck, and or the manifold heat crossover is plugged, this could add to the problem. And there is no doubt that adding a later model air filter with "snorkel heat" will not hurt in that climate

Also bear in mind that "carb icing" does NOT have to happen when the temperature is all that cold. Humidity plays a HUGE factor, so a humid 50 degree day can cause you heartache if the carb is "running cold."

 

[70DartMike]

Mike....Ideally, what you need is to get heat in the intake air stream. That will warm the carb just enough to stop the icing and fuel puddling when cold. Once the engine gets nicely warmed up, the problem disappears. Maybe check with the auto wreckers around these parts....you may be able to adapt the later setup to work with your early exhaust manifold.

A lot of people removed this equipment mistakenly thinking it was part of the emission control system, which it is not.

I have numerous air cleaners which I believe have the adapter for it, so that's no problem. Where does the heat come from though, the exhaust manifold? If so, how do I get heat from it? I seem to recall some sort of thin sheet metal piece which funneled (spelling?) the heat to the air cleaner. Where would I find a piece for that? .. I've got the exhaust manifolds which look like smaller 340 manifolds.. know the type I mean?

 

[67Dart273]

Yup. Theres a tin "stove" over/ around part of the exhaust manifold, and a piece of weird hi-temp composition foil/??? tube that connects the stove to the air filter

If you download the 72 service manual posted in the thread, I'm sure you can find some good photos/ diagrams of it. You could MAKE what you need out of sheet metal. Doesn't have to be all that "precision" the big thing would be keep it cutting up plug wires and annoyingly rattling.

http://www.forabodiesonly.com/mopar/showthread.php?t=132309&highlight=manual,+download

 

[65Val]

I have numerous air cleaners which I believe have the adapter for it, so that's no problem. Where does the heat come from though, the exhaust manifold? If so, how do I get heat from it? I seem to recall some sort of thin sheet metal piece which funneled (spelling?) the heat to the air cleaner. Where would I find a piece for that? .. I've got the exhaust manifolds which look like smaller 340 manifolds.. know the type I mean?

Here's a better shot of the system. You need the air cleaner housing with snorkel AND functioning temperature/vacuum switch (to open and close the flapper valve at the correct time), the manifols heat stove, and connecting pipe.

How do I get heat from it?

The carb pulls air into itself, as usual, and ,with the flapper valve closed, the heated air is drawn up the pipe from the "stove" that's attached to the exhaust manifold, and down the carb throat, heating the carb as it goes.