automatic choke operation

[fordor41]

Decided to hook up the auto choke on my carb (SBF 2 brl). I cleaned out the hole in the exhaust manifold so the heat tube would slide in and noticed that it appears to be a blind hole. how can heat travel up the heat tube to the choke housing to open the choke if the hole in the manifold is a blind hole. I assume there is some sort of vacuum assist from the choke housing but with a blind hole how does the heat travel?

[rotorwrench]

I agree. Most all heat riser tubes have at least some circulation through the hot manifold (it just needs heat, not exhaust) but it won't work well without the ability to flow hot air with a carb vacuum port to aid the flow. What is the origin of the engine/manifold sbf combination? Maybe the manifold pathway is crusted up with corrosion of something.

[scicala]

If it becomes an major issue and a lot of work to correct it, you can always buy a Holley electric heated choke thermostat cap for $15 all day long. Supply it with 12V when the ignition is on, then a short ground wire, and your all set. There should be a vacuum pulled through the choke housing on the carb which keeps it from overheating and pulls the air through.


Sal

[40 Deluxe]

What year carb and manifold? Most shop manuals for whatever year you have will show the heat tube setup. It varies between years and engine models.
Definitely you do not want exhaust gasses in the heat tube! It will clog and corrode the choke mechanism in no time. This was common back in the day and parts houses had various repair kits to bypass the clogged/burned out factory tubes.

[rotorwrench]

I think the old mustangs and similar cars with 289 & 302 engines had a kind of steel wool inside the stove to act as a filter for the air being drawn in from down on the bottom of the stove part. A person may have to take the manifold off and see what can be done to restore proper function. PITA for sure but working on it in the confines of an engine compartment is a PITA too.

[fordor41]

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I removed the manifold ( mid '70's Ford truck) and don't see any evidence of a passage way out of the blind hole. Agree that exhaust gasses are a bad thing in the choke housing.
went thru'59-'65 Motors manual and a '81 Ford manual. they show the heat tube/choke and manifold but nothing as to how it works. I've had a lot of '60's-'80's fords but never thought of how it should operate. As I remember the heat tubes were a tight fit in the manifold

[40 Deluxe]

Originally Posted by fordor41

I removed the manifold ( mid '70's Ford truck) and don't see any evidence of a passage way out of the blind hole. Agree that exhaust gasses are a bad thing in the choke housing.
went thru'59-'65 Motors manual and a '81 Ford manual. they show the heat tube/choke and manifold but nothing as to how it works. I've had a lot of '60's-'80's fords but never thought of how it should operate. As I remember the heat tubes were a tight fit in the manifold

Try a blast of compressed air to see if that opens it. Or run a small drill bit in by hand-any carbon will be dug out easily but if you hit metal you won't damage the tube.
Another thought: By the '70's at least some Fords were using hot air pipes from the exhaust manifold to the air cleaner with doors that let in heated air when cold and then opened to let in cool air after the engine warmed up, and also electric chokes. So your manifold and original carb may not have had a heat tube for the choke!
Do you the exact year of the carb and manifold? There should be a metal tag on top of the carb with a date code such as 'E4' which would be 1974.

[rotorwrench]

If it looks like the one in the link, then it has a similar stove to the ones made in the 60s. https://www.ebay.com/i/182743884683?chn=ps

I'm not sure if the bottom part of the stove can be removed or not if it's too crusty. Some folks just get a long drill bit and drill though but it needs to have filtered air passing through the system.

The thermally controlled induction air heating system is a separate system. PCV and EFE (early fuel evaporation) systems started showing up around 1962 and were the first of the emission controls.

[fordor41]

Originally Posted by rotorwrench

If it looks like the one in the link, then it has a similar stove to the ones made in the 60s. https://www.ebay.com/i/182743884683?chn=ps

I'm not sure if the bottom part of the stove can be removed or not if it's too crusty. Some folks just get a long drill bit and drill though but it needs to have filtered air passing through the system.

The thermally controlled induction air heating system is a separate system. PCV and EFE (early fuel evaporation) systems started showing up around 1962 and were the first of the emission controls.

pretty much exactly like that one. found one on the ole interweb, on a mustang and the round area in the center of the 1st pic had a hole for the air to feed up thru the manifold casting and into the heat tube to the choke. extra hole had a tube that led to the air cleaner to supply clean air. time to do some digging. thanks for replies

[fordor41]

Originally Posted by rotorwrench

I think the old mustangs and similar cars with 289 & 302 engines had a kind of steel wool inside the stove to act as a filter for the air being drawn in from down on the bottom of the stove part. A person may have to take the manifold off and see what can be done to restore proper function. PITA for sure but working on it in the confines of an engine compartment is a PITA too.

Actually removing the manifolds from my '41 w/ 302 is a piece of cake. disconnect header pipe, remove 8 manifold bolts and it slides right out. Love those Ford engines!