Perhaps just the goal of getting the car to run well. Were the goal to have the sense of achievement (literary license here) of accomplishing the repair, rebuilding the old one might be better.
There is probably a tube from the exhaust manifold to the part of the carburetor that holds the automatic choke spring. This tube is called the “choke stove”. The head from the exhaust manifold causes this spring to expand and open the chock damper. If the choke stove is broken or otherwise defective, no heat gets to this thermostatic spring and the choke won’t open. Check this before buying a new automatic choke spring.
If it were my car, I would convert it to a manual choke. Ford was one of the last manufacturers to retain the hand choke. I know many Ford models through the 1960’s had hand chokes and I always thought that retaining thehand choke was a plus for Ford.
Caddyman, I had a shop teacher in the 60’s (Mr Berry was his name) that said the same thing happened when self adjusting brakes came out, many mechanics were either asked to take the self adjusters off, or told their customers to take them off.
This was in the days where people actualy debated if drum brakes were better than disc, very passionate debate
Since the choke seems to stay opened or closed by adjusting it I think your thermostat is ok, If I remember correctly to start the car you first need to pump the gas pedal once to turn on the choke. It will stay open by itself until you do so.
I’ve rebuilt some carbs with great success. I use a carb cleaner in a spray can to clean out the jets and passages, and use ‘simple green’ and a couple of brushes to clean the outer body parts and plates. I’ve never had them so dirty they needed a caustic bath to clean up. Like the OP, the most of them I deal with have simply become hard to tune and need jut a clean up and new gaskets.
Pumping the gas does three things. It allows the chole to close, it enables the throttle plate linkage to set onto the high idle cam, and it primes the engine with a spray of gas from the accelerator pump. Until you do this, the accelerator linkage normally goes up against the high idle linkage and that keeps the choke from closing.
It may be confusing to use the word thermostat here. Choke control or the more formal names like bimettalic coil keep the item from being confused with the cooling system thermostat.
Right you are. I remember unlearning pumping the gas when FI came along, suppose not pumping the pedal is the answer, once the bimettalic coil is readjusted? Choke and carb cleaner in a can ma be needed also.
Yup. Perhaps a readjustment and cleaning is all that’s needed, however the problem with old carbs is that the parts wear. The shafts for the choke and the throttle plate can wear grooves in them, float linkage cane become sticky, floats can either leak or saturate (depending on the float material), accelerator pump linkage can wear, etc. Since the OP was considering rebuilding it, my thought was that just buying one already rebuilt made more sense.
Would saying that turning that OEM carb as a core would hurt the cars “originality” be overkill?
It might of the car were fully documented and shown. If not, a properly operating vehicle is worth more than an all original that doesn’t run right.
I think pumping the gas pedal to set the choke is the problem. I do not understand your question Oldschool, I think a manual choke in my estimation of a classic would be an obvious after market patch job. Please explain “Would saying that turning that OEM carb as a core would hurt the cars “originality” be overkill?”
The question is base upon the idea of maintaining all the original equipment the car came with. Some think that Mustangs (even 6 cylinder Mustangs, are collectible and value them more if intact, even down to the original carburator). I can’t believe you needed that explained, but stranger things have happened
I was looking at if he put in a manual choke control that would certainly be a detriment, if he got a rebuilt carb of the same model how would one know or care, I am not that into it I know the answer, thanks.
They have tags on them and “people in the know” look for these signs of originality.
Thanks for all the advice. We have now been able to locate a source and purchased the thermatic spring. The question we seek now is what are the proper steps that we need to follow in order to get this set correctly? I assume that settings are based on the outside temperature. We are still have some cool mornings < 50 degrees.
Thanks ahead of time for the responses.
You should see a scribed line on the carburator body where the thermatic spring mounts. There will be a corresponding line on the housing of the spring. Mount the thermatic spring housing line to the lean (-) side of the line on the carurator body – leaving the mount screws loose so you can still turn it. As you rotate the thermatic spring housing to line up with the body line you should feel the spring hook grab the tang on the choke lever and try to close the choke. Tighten down the mounting screws when the lines are together.
When you open the throttle with the engine off the choke should now snap almost closed. Now try starting the engine cold. If the engine does not start but a shot of ether will get it going, move the housing line to the + side of the carburator body reference line. If the engine floods, move the housing line to the - side of the body line. It is a little bit of a cut and try affair.
You will have to also make sure the vacuum break is working and set correctly. When everything is right, the choke should go completely closed before the cold engine starts; the vacuum break should the choke plate open about an 1/4 inch when the engine catches; and the the engine should run and accelerate smooth as it warms up. Spitting and back fire up the carburator requires a little richer (+ direction). Sputtering and black exhaust smoke requires going a little leaner (- direction),
Let us know where you are on this situation and we can go from there.
As stated previously your spring appears to be fine based on the fact you can make it all the way open or all the way closed. Before replacing the spring, pump the pedal one time to actuate the choke. if it does not close adjust the existing until it just barely closes. That is a good starting point. Return the part if you can because I do not think it is needed.
The spring is heated by electricity. I’ve never had to replace one, but I’d leave the choke in the same position to start. There are marks on the black plastic houseing and the metel base of the carb. Note where they are and reset at the same place.
I think it should take about 5 mins. of current to the choke spring for it to hold the choke in the full open position. As long as the the choke is fully closed when cold (you have to press the gas petal down one time to set the choke) the car should start fine. Then just drive and see how the car drives as it warms up. If you get a minium to zero stumbling until the temp gauge registers in the middle area the choke is set fine. If it doesn’t fun smoothly while warming up you can move the choke marks and it is a matter of trial and error until you get a setting that works.
I’d tend to have the choke open up sooner even if it means a little stumbling as that will dump less raw gas into the motor as it warms up.
Thanks for the info. Once we replaced the spring - I hooked the tang into the spring at the start - that is there was a round section on the spring and i just place the tang into it - and did some adjustments it is now starting.
There are times when it takes a little bit to get it started but, it does start with out opening the hood and closing the choke. I am sure that there will be some adjustments when we get back into winter.
Update. After doing a complete rebuild of the carburetor and tune up the car starts fine.