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Discussion Starter #1
I've had my 61 since Dec. and it runs nice and clean, so I've never bothered to pull the air filter until yesterday. Too many other things to fix. I noticed there is a large externally threaded fitting on the choke housing facing to the back of the engine. It looks like someone tore it all up with vice grips or something. I put my finger over it and it pulls a lot of vacuum. I couldn't find anything about it in my shop manual yet. I sprayed carb cleaner around it and the RPMs increased. Is it for a PVC valve? I don't see a place for a PVC on the intake. Even though it seems to be pulling a lot of vacuum, I plugged it and it didn't seem to have any noticible affect. I'm guessing at a minimun, it had to be pulling in dirt. The air mixture screws at the base of the carb are around 6 turns out. I thought they were usually around 2-2 1/2 turns out? Sorry, but I have very little knowledge of carbs. Any help or suggestions are appreciated.
Karl.
 

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If it is a Ford carb the fitting is probably for the hot air tube that comes up from the exhaust manifold.
 

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If it is a Ford carb the fitting is probably for the hot air tube that comes up from the exhaust manifold.
Pulling A Vacuum? I wouldnt think so, but maybe... I would make the S.W.A.G. as PCV. IF the carb is in fact a Ford carb...
 

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I've had my 61 since Dec. and it runs nice and clean, so I've never bothered to pull the air filter until yesterday. Too many other things to fix. I noticed there is a large externally threaded fitting on the choke housing facing to the back of the engine. It looks like someone tore it all up with vice grips or something. I put my finger over it and it pulls a lot of vacuum. I couldn't find anything about it in my shop manual yet. I sprayed carb cleaner around it and the RPMs increased. Is it for a PVC valve? I don't see a place for a PVC on the intake. Even though it seems to be pulling a lot of vacuum, I plugged it and it didn't seem to have any noticible affect. I'm guessing at a minimun, it had to be pulling in dirt. The air mixture screws at the base of the carb are around 6 turns out. I thought they were usually around 2-2 1/2 turns out? Sorry, but I have very little knowledge of carbs. Any help or suggestions are appreciated.
Karl.
6 out seems excessive to me also.... Maybe time for a kit? How does the car actually run? As I said in previous post I would guess the big fitting is for the PCV...
 

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Doubt there ever was a PCV valve on any '61...sounds like the hot air intake fitting, used to heat up the choke spring so the choke will shut off after the engine gets so warm. If you have the original exhaust manifold, there should be a couple of holes or a fitting on it that two tubes attach to. One tube draws filtered air from the air cleaner, the other tube allows the now heated air to be drawn into the engine via the choke housing. 50 years after the car was built, there is very little chance that any of the original set-up is still functioning, IF it's even there...not too hard to fabricate something to duplicate the factory system, though.
 

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Doubt there ever was a PCV valve on any '61...sounds like the hot air intake fitting, used to heat up the choke spring so the choke will shut off after the engine gets so warm. If you have the original exhaust manifold, there should be a couple of holes or a fitting on it that two tubes attach to. One tube draws filtered air from the air cleaner, the other tube allows the now heated air to be drawn into the engine via the choke housing. 50 years after the car was built, there is very little chance that any of the original set-up is still functioning, IF it's even there...not too hard to fabricate something to duplicate the factory system, though.
PCV systems were required on Pass Cars starting in 1961 in California but a picture would stop 99% of the guess work.
 

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PCV systems were required on Pass Cars starting in 1961 in California but a picture would stop 99% of the guess work.
Didn't know the PCV system went back that far...not surprising it would be CA...but either way, the choke housing is not where the cranckcase fumes/droplets were vented.
 

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there is a large externally threaded fitting on the choke housing facing to the back of the engine.
Hey Mr. CTS,
Go here:

Autolite 4100 1.12 C4AF-9510 DG Carburetor

Scroll down to the 17th JPG.

Is the fitting at which the Blue Pen is pointing the threaded fitting to which you are referring?

If it is, THAT is the Choke Heater Fitting.

If you have an electric Choke Cap, you can just cap that threaded tube..

Or if you want to return your Carburetor to its ORIGINAL functioning, you can get a fitting for your Manifold from Greg Donahue.

It is called a Choke Heat Chamber Assembly, Part Number: C3AZ-9890A

HTH

JC
 

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Discussion Starter #10
Hopefully this pic goes through. For what I know about Fords, I believe this is a Ford 2100 on a 352 3 spd. car. The previous owner said he had a carb fire. To what extent, I only know that the hood is in primer and there is no insulation. The carb and air cleaner look nice, so is it orginal to the car? There is also a tube sticking down from the carb[in the background]. What is that? Screws missing from the housing too but doesn't seem to be leaking at the carb.
 

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Hopefully this pic goes through. For what I know about Fords, I believe this is a Ford 2100 on a 352 3 spd. car. The previous owner said he had a carb fire. To what extent, I only know that the hood is in primer and there is no insulation. The carb and air cleaner look nice, so is it orginal to the car? There is also a tube sticking down from the carb[in the background]. What is that? Screws missing from the housing too but doesn't seem to be leaking at the carb.

That carb has been converted to an electric choke so it doesn't use the hot air tube system at all. You can see the threaded fitting with nothing attached...I suppose the vacuum source for the original choke was blocked where the choke body mounts to the carb body...at least I hope it's blocked. The fitting/nipple in the upper part of the photo is where the hose that used to supply filtered air the choke system was connected to the carb.

No PCV on that car, though.
 

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Screws missing from the housing too but doesn't seem to be leaking at the carb.
Hey Mr. CTS,
The Screws that are missing were to hold the Bracket that held the Heater Hose to the side of the Choke Cap to keep it heated after the hot air from the Exhaust Manifold had opened the Choke, which activated the little Piston in the Choke Mechanism, which when opened, closed off the orifice that permitted the Engine vacuum to draw the heated air from the Fitting in the Exhaust Manifold.

JC
 

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The heated air is always pulled thru the choke housing and then into the engine in order to keep the thermo spring hot and to maintain proper carb calibration. The manual spells this out pretty clearly and that's why disabling the stock choke system can mess with the air/fuel ratio of the original carb boosters and jets combination...the whole intake charge becomes richer...similar problems occur when changing to or from a PCV system as it messes with the carb calibration.
 

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rambutt is correct, except the size of the leak hardly affects the main metering. you would need to adjust the idle mix though
 

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that is manifold vacuum-meaning it comes from below the throttle plates. any air entering the manifold which doesn't go through the venturis affects mixture
 

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that is manifold vacuum-meaning it comes from below the throttle plates. any air entering the manifold which doesn't go through the venturis affects mixture
Bingo...that's why manual choke(HiPo 289), road draft tube, and PCV engines have different boosters for otherwise identical engines. PCV and auto choke designs BOTH introduce a controlled vacuum leak directly into the intake manifold, bypassing the carb metering. IF the auto choke vacuum source was above the throttle plates, there would be virtually no vacuum to pull the hot air thru the choke housing.

And true, the PCV system is a bigger "leak" than the auto choke "leak", but they are both accounted for to some degree from the factory by the use of different booster clusters and sometimes accel pump settings.
 

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The vacuum leak has to be capped (blocked) if not using the hot air feature.

It will not only throw the calibration of the carb off but will introduce unfiltered outside air.

The heated choke shown is only an electric assist. It draws approx. 7V and will not operate the choke properly if the hot air feature is non-operational. You will need a HOLLEY choke kit (12V)
 
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