Stromberg Question

dillardrg

dillardrg

Pre-takeoff checklist
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Ron Dillard
I have a 46 J3 with a C-85-12 engine with a Stromberg Carb.
During the annual my AI noticed that my carb does not have a mixture control lever.
Not only does it not have a mixture control lever but all the parts normally inside the mixture chamber are missing and a smooth convex cover caps the chamber.
Using the NA-S series parts illustration all the parts #47 through #61 are missing.
I know that if all these parts are present, the mixture control lever would normally be safetied to the full rich position in this installation.
Is my carb legal in this configuration i.e. missing all these parts?
Will I have to replace all the mixture chamber parts and safety the mixture lever to the full rich position to be legal?

Comments please.
 
dillardrg said:
I have a 46 J3 with a C-85-12 engine with a Stromberg Carb.
During the annual my AI noticed that my carb does not have a mixture control lever.
Not only does it not have a mixture control lever but all the parts normally inside the mixture chamber are missing and a smooth convex cover caps the chamber.
Using the NA-S series parts illustration all the parts #47 through #61 are missing.
I know that if all these parts are present, the mixture control lever would normally be safetied to the full rich position in this installation.
Is my carb legal in this configuration i.e. missing all these parts?
Will I have to replace all the mixture chamber parts and safety the mixture lever to the full rich position to be legal?

Comments please.
Click to expand...


Ron,

I've found the Aeronca Type Club to be of immense help in these sorts of technical questions -- I'm sure the same exists for your J-3.

(My Chief has a Stromberg as well, with a mixture knob on the firewall safety wired in position)
 
Thanks Dan,

I did ask the question there as well, trying to get as much information as possible.
 
dillardrg said:
I have a 46 J3 with a C-85-12 engine with a Stromberg Carb.
During the annual my AI noticed that my carb does not have a mixture control lever.
Not only does it not have a mixture control lever but all the parts normally inside the mixture chamber are missing and a smooth convex cover caps the chamber.
Using the NA-S series parts illustration all the parts #47 through #61 are missing.
I know that if all these parts are present, the mixture control lever would normally be safetied to the full rich position in this installation.
Is my carb legal in this configuration i.e. missing all these parts?
Will I have to replace all the mixture chamber parts and safety the mixture lever to the full rich position to be legal?

Comments please.
Click to expand...
It's legal. Lots of those carbs were set up that way. Simple airplanes.

Those parts are hard to find. I have a Stromberg on my homebuilt, and machined the valve parts for the mixture. Seldom use it, though.

Dan
 
Dan Thomas said:
It's legal. Lots of those carbs were set up that way. Simple airplanes.
Dan
Click to expand...

Dan,

Do you have any documentation? I can't find anything that shows the carb without the mixture control lever sticking through the chamber cover. Any help would be appreciated.

Thanks,
 
dillardrg said:
Dan,

Do you have any documentation? I can't find anything that shows the carb without the mixture control lever sticking through the chamber cover. Any help would be appreciated.

Thanks,
Click to expand...

I think I saw something in the way of a service bulletin from Precision but I'm not certain that was it. I do know that the mixture control on some of these carbs was considered to be ineffective even when all the parts were in place and working correctly, although it's also my understanding that this wasn't really true at cruise power, the reality is it has no effect only at idle.
 
gismo said:
I think I saw something in the way of a service bulletin from Precision but I'm not certain that was it. I do know that the mixture control on some of these carbs was considered to be ineffective even when all the parts were in place and working correctly, although it's also my understanding that this wasn't really true at cruise power, the reality is it has no effect only at idle.
Click to expand...
Yes, the mixture works by applying back suction on the bowl from the venturi - so it don't do nuthing at idle. If nothing is broken, it will work fine at cruise / full power.

Am I reading between the lines or is the OP having a problem with his AI not signing off on the annual because the carburetor didn't come with the mixture control parts when it was new?
 
Capt. Geoffrey Thorpe said:
Yes, the mixture works by applying back suction on the bowl from the venturi - so it don't do nuthing at idle. If nothing is broken, it will work fine at cruise / full power.

Am I reading between the lines or is the OP having a problem with his AI not signing off on the annual because the carburetor didn't come with the mixture control parts when it was new?
Click to expand...

Sounds like it although I sense a possibility that when the airplane was new the carb on the engine had the parts (probably wired to full rich) and that at some point a carb sans mixture control parts showed up. But for all I know the mixture control components weren't there when the plane flew for the first time and/or mixture control might have been an option on the plane and/or engine TCDS.
 
dillardrg said:
I have a 46 J3 with a C-85-12 engine with a Stromberg Carb.
During the annual my AI noticed that my carb does not have a mixture control lever.
Not only does it not have a mixture control lever but all the parts normally inside the mixture chamber are missing and a smooth convex cover caps the chamber.
Using the NA-S series parts illustration all the parts #47 through #61 are missing.
I know that if all these parts are present, the mixture control lever would normally be safetied to the full rich position in this installation.
Is my carb legal in this configuration i.e. missing all these parts?
Will I have to replace all the mixture chamber parts and safety the mixture lever to the full rich position to be legal?
Comments please.
Click to expand...

IIRC, not all Strombergs came with those parts. Some have been removed over time. Frankly, if your Stromberg works properly, leave it alone. Those parts are not widely available.

Deb "owner of three Strombergs"
 
You need the production certificate to get the proper dash numbers that were produced without a mixture control.
 
gismo said:
Sounds like it although I sense a possibility that when the airplane was new the carb on the engine had the parts (probably wired to full rich) and that at some point a carb sans mixture control parts showed up. But for all I know the mixture control components weren't there when the plane flew for the first time and/or mixture control might have been an option on the plane and/or engine TCDS.
Click to expand...

i flew an Aeronca 7AC that had never had the control parts, just a factory-made cover. Wiring the control full rich does exactly the same thing as taking all the guts out and putting that cover plate on: it just vents the bowl to the dead-air cavity behind the venturi and lets the tiny suction port suck air from the cavity. The mixture contol worked by gradually closing off the port to the dead-airspace, allowing the suction to hold back on the fuel in the bowl.

I have an ancient Champ parts manual somewhere. If I can find it, we might see the carb breakdown showing the blank cover plate.

Go here, maybe: http://www.mechanicsupport.com/manuals.htm


Dan
 
Last edited:
Capt. Geoffrey Thorpe said:
Am I reading between the lines or is the OP having a problem with his AI not signing off on the annual because the carburetor didn't come with the mixture control parts when it was new?
Click to expand...

We don't have a clue as to how the carb was set up when new. Right now it does not have any parts in the mixture chamber and I can't find any documentation that this is legal, or that any came new like this.
 
Tom-D said:
You need the production certificate to get the proper dash numbers that were produced without a mixture control.
Click to expand...

Tom,
I have searched for a productdion ceretificate but no luck, do you know where I could find such an animal?
 
N1347B said:
IIRC, not all Strombergs came with those parts. Some have been removed over time. Frankly, if your Stromberg works properly, leave it alone. Those parts are not widely available.

Deb "owner of three Strombergs"
Click to expand...

Deb,

I would love to just leave it alone, but my AI insists that I find proof that it is legal.
 
I attached an authoritative sounding but unofficial document from the Cessna 120/140 archives that claims that no AD or Service Letter exists to officially deactivate the mixture controls.

I know more about the Rochester Quadrajet than the Stromberg. I went to an upscale Boca Raton car dealership with my college room-mate so he could get a small brass screw for his old Jaguar downdraft carb. He paid $24 dollars for it (a kings ransom at that point in our lives). I was startled and he said: "thats nothing, I really only need the little o-ring around the screw" I once wrote an uunet article on how the Stromberg works to "automatically" adjust the mixture. Based on tonights google-ing I was probably wrong.

You might e-mail the dude who wrote it, the address is in the PDF.

Good luck!
 

Attachments

  • stromberg_mixture___secrets.pdf
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dillardrg said:
Deb,

I would love to just leave it alone, but my AI insists that I find proof that it is legal.
Click to expand...

It is a horrible thing to fall into the hands of an uneducated IA. Those of us who fly vintage airplanes avoid the modern IA like the plague.

Stromberg developed and sold many models of their carbs without mixture components.

The NA-S2, NA-S3, and the NA-S3B models are equipped with cover plates only.

Most of the airplanes that came equipped with these Strombergs were not built with a mixture control in the panel, so they were wired rich at the factory or a non mixture model was installed. If there is not logbook entry that your carb was replaced since the airplane was manufactured, then the part is original. To add these parts (if they can be found) would not conform to its TDC.

Deb
 
N1347B said:
It is a horrible thing to fall into the hands of an uneducated IA. Those of us who fly vintage airplanes avoid the modern IA like the plague.

Stromberg developed and sold many models of their carbs without mixture components.

The NA-S2, NA-S3, and the NA-S3B models are equipped with cover plates only.
Click to expand...

Would that be the 384407 "Plate- Mixture cover replacement" used in place of the P-61037 "Cover Assembly - Mixture control" ?

http://www.mykitplane.com/Planes/PeoplesFiles/Stromberg NAS3A1, C-series Cont.pdf see listing for #55
 
twdeckard said:
I attached an authoritative sounding but unofficial document from the Cessna 120/140 archives that claims that no AD or Service Letter exists to officially deactivate the mixture controls.

I know more about the Rochester Quadrajet than the Stromberg. I went to an upscale Boca Raton car dealership with my college room-mate so he could get a small brass screw for his old Jaguar downdraft carb. He paid $24 dollars for it (a kings ransom at that point in our lives). I was startled and he said: "thats nothing, I really only need the little o-ring around the screw" I once wrote an uunet article on how the Stromberg works to "automatically" adjust the mixture. Based on tonights google-ing I was probably wrong.

You might e-mail the dude who wrote it, the address is in the PDF.

Good luck!
Click to expand...

Very informative, Thanks
 
N1347B said:
It is a horrible thing to fall into the hands of an uneducated IA. Those of us who fly vintage airplanes avoid the modern IA like the plague.

Stromberg developed and sold many models of their carbs without mixture components.

The NA-S2, NA-S3, and the NA-S3B models are equipped with cover plates only.

Most of the airplanes that came equipped with these Strombergs were not built with a mixture control in the panel, so they were wired rich at the factory or a non mixture model was installed. If there is not logbook entry that your carb was replaced since the airplane was manufactured, then the part is original. To add these parts (if they can be found) would not conform to its TDC.

Deb
Click to expand...

R&W. Geoff and Deb, If these came without the mixture parts there should be some documentation, I will keep looking.

Thanks
 
Capt. Geoffrey Thorpe said:
Would that be the 384407 "Plate- Mixture cover replacement" used in place of the P-61037 "Cover Assembly - Mixture control" ?

http://www.mykitplane.com/Planes/PeoplesFiles/Stromberg NAS3A1, C-series Cont.pdf see listing for #55
Click to expand...


Geoff, I think you have nailed it :cheers:. That listing for #55 is used only on the NA-S3B model and none of the other mixture parts are listed for that model. Also, #54 listed for the 3B is "Gasket-Mixture control cover replacement plate.
Also, the NA-S2, 3, and 3A do not list any of the mixture parts, only the NA-S3A1 and the NA-SO3A1 list the mixture parts.
This is what I was looking for:D.

Thank you Thank you Thank you
 
Rotor&Wing said:
He (the IA) has the resources to do that. Have him do it.
Click to expand...

He might, too, at shop rates. Gets expensive.

I'm glad Geoff found that. I looked everywhere and couldn't find such a document. Excellent stuff.

Dan
 
dillardrg said:
Geoff, I think you have nailed it :cheers:. That listing for #55 is used only on the NA-S3B model and none of the other mixture parts are listed for that model. Also, #54 listed for the 3B is "Gasket-Mixture control cover replacement plate.
Also, the NA-S2, 3, and 3A do not list any of the mixture parts, only the NA-S3A1 and the NA-SO3A1 list the mixture parts.
This is what I was looking for:D.

Thank you Thank you Thank you
Click to expand...

That's why they pay me the big bucks here.

:rofl:
 
dillardrg said:
Tom,
I have searched for a productdion ceretificate but no luck, do you know where I could find such an animal?
Click to expand...


Ask FSDO to provide it..I would ask mine, but he would want to know what aircraft I was working on and that would lead to him playing 20 questions with me.
 
I would ask the IA to call FSDO, and simply tell them the Carb model, and serial number and ask if it requires a the mixture plates to be installed.

some do, some don't. ( as DEM has pointed out)
 
Tom-D said:
I would ask the IA to call FSDO, and simply tell them the Carb model, and serial number and ask if it requires a the mixture plates to be installed.

some do, some don't. ( as DEM has pointed out)
Click to expand...

Uh, did I hear someone suggest getting the FEDs involved:no:
 
Ron Dillard. You got lots of information and much more mis-information. Excepting special installations as a result of STC's or special 337's, the TCDS for the plane lists the Engine for that particular plane. It took a while, but I found the TCDS for the J-3 () which calls out Continental engines and its list includes the C-85-12. The TCDS for the C-85 () calls out the permissible carburetor and it names ONLY the NA-S3A1, with the mixture control. Your engine (unless an STC changed it) requires the NA-S3A1 and EXCLUDES THE NA-S3B! Now for the guessing. Somebody installed the wrong carburetor, maybe because that was all there was (no C-85 () should have it) or he intended it for a temporary test and was sure that the plane would never be flown high. If you have read my article listed as from the International Cessna 120/140 club, you can sense how I feel so strongly that every C-85/90 should have the mixture control. ALL! the carburetors authorized for our small engines are equally effective at all altitudes except the Stromberg is not effective at low engine speeds.
The TCDS for the plane calls out the engines authorized.
The TCDS for the engine (s) calls the carburetors.
The model number of the carburetors calls out the parts and features of the carb.

Your engine should have the NA-S3A1, and it should have the mixture control.
Try it, you might like it.

If you need any other of my carb aricles, let me know.

Neal F. Wright
 
Thanks Neal, I have a copy of A-691, the model of carb was never a question.
Your article was very informative and it looked like you spent a lot of hours researching.
Good stuff.
 
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