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Suggestion for Stromberg repair - re-jet

A

Ab0ngcd

MEMBER
I have a NA-S3A1 391229-1-2 carb off a C-90 that was overhauled in 2010, but only 40 hours on it before 2013, then it sat until 2020, when it when it was fueled up and run for 20 more hours. It has started weeping, and I am putting it on a C-85. So it only has about 60 hours on it.

It should only need new gaskets, new jets, new needle and seat, and adjustment. So far my only estimate is for a complete overhaul. Any suggestions for someone or a company that does Stromberg repairs?
 
Ab0ngcd said:
It has started weeping,
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Where are the weeps? If it is at the parting surface between the two halves, try snugging up on the screws. Likely the gasket dried from lack of fuel. Is it dripping from the venturi section? Perhaps Leaking float?
 
just a comment, when you say only need, that is a complete overhaul on those carbs, pretty simple. not sure what else your thinking, but once its apart its apart and everything is checked.
 
I'm in the middle of overhauling my Stromberg right now. Get yourself the stromberg manual from Aircraft Spruce and compare the orifice sizes (drill sizes) with your carb against the C85 carb. There are differences in the fuel metering jet as well as some others.

Best bet is to send it to the Stromberg Specialist http://thestrombergspecialist.com/ if you can swing the rebuild cost. There are a couple service bulletins, one for drilling a new idle air passage in the upper carb casting that can be tricky but is much needed for fixing the leaking issue especially on aircraft with higher AOA in 3 point.

From my experience so far with rebuilding the carb, it can be done but if you add up your time, tools, and mistakes made/learned from it's cheaper to pay the $975 and get a perfect carb that's fully updated back from that guy.
 
I thought that a real "overhaul" would include disassembly of the throttle butterfly mechanism and checking dimensions, rebushing the throttle shaft, replacement of the throttle shaft, all the moving parts that wear out over 1000 hours. They also mentioned re-painting the housing. The paint is pristine, the throttle shaft and bushing are not worn, as far as i know. Things like that that double the price differentiating fro a repair and and overhaul. If it wasn't for the re-jet, all it should need is checking the float and if needed, replacing the needle and seat. Plus a gasket set.

The weeping is from the venturi section. So it could be the float.


Anyway, that was my guess. I would like to not shell out $1000. I did get a $775, but that did not include the jets, which they may not have.

I will contact Columbia.

Edit: Present carb had SB 73 and SB 84 complied with. Those are the higher drilling onf the housing and the delrin needle.

Thanks!
 
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Crash said:
I'm in the middle of overhauling my Stromberg right now. Get yourself the stromberg manual from Aircraft Spruce and compare the orifice sizes (drill sizes) with your carb against the C85 carb. There are differences in the fuel metering jet as well as some others.

Best bet is to send it to the Stromberg Specialist http://thestrombergspecialist.com/ if you can swing the rebuild cost. There are a couple service bulletins, one for drilling a new idle air passage in the upper carb casting that can be tricky but is much needed for fixing the leaking issue especially on aircraft with higher AOA in 3 point.

From my experience so far with rebuilding the carb, it can be done but if you add up your time, tools, and mistakes made/learned from it's cheaper to pay the $975 and get a perfect carb that's fully updated back from that guy.
Click to expand...


not that theres anything wrong with him, which ive never done business with, but saying hes your best bet, please explain???
 
Ab0ngcd said:
I thought that a real "overhaul" would include disassembly of the throttle butterfly mechanism and checking dimensions, rebushing the throttle shaft, replacement of the throttle shaft, all the moving parts that wear out over 1000 hours. They also mentioned re-painting the housing. The paint is pristine, the throttle shaft and bushing are not worn, as far as i know. Things like that that double the price differentiating fro a repair and and overhaul. If it wasn't for the re-jet, all it should need is checking the float and if needed, replacing the needle and seat. Plus a gasket set.

The weeping is from the venturi section. So it could be the float.


Anyway, that was my guess. I would like to not shell out $1000. I did get a $775, but that did not include the jets, which they may not have.

I will contact Columbia.

Edit: Present carb had SB 73 and SB 84 complied with. Those are the higher drilling onf the housing and the delrin needle.

Thanks!
Click to expand...


the guys that know the carbs can tell things just holding it in there hands. at columbia ask for doug.
 
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One of the simplist carbs ever built, 1940s tractor carb. Easy to take apart and put back together. If you sink the float in boiling water it will tell you if it's leaking by blowing bubbles. Get a can of carb cleaner that has a spray wand and blow it thur the passages to see if they are clear. You can push 30-40 lb mono fishing line thru them also.

Plan B Find a grey old farmer and give it to him and he will fix it on his kitchen table while watching Wheel of fortune

Glenn
 
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tempdoug said:
not that theres anything wrong with him, which ive never done business with, but saying hes your best bet, please explain???
Click to expand...

When someone dedicates their entire business to rebuilding one specific brand and model of carb, has basically written the book on how they work and how to rebuild them, and has amassed a massive collection of every type of discontinued part out there, I think it's safe to say that person is the best at that niche.

In this case it's Bob and all he does is rebuild Stromberg NAS3 carbs. I'd say that qualifies him to be the "best" at it.

I'm not saying that's the absolute best option for every case as evidenced by how many Strombergs have been rebuilt by amateurs but if you have the money and want your Stromberg to be absolutely perfect and rebuilt 100% to original spec then the Stromberg Specialist is pretty much the only game in town.

I'd also like to remind that the original post was mentioning taking a C90 carb and converting it to a C85 set up carb. This is not a simple rebuild/tune but rather probably one that will need new jets purchased and the carb blueprinted against the C85 carb specs. Best to get a specialist to do it unless the OP is extremely detail oriented and checks all the orifice sizes and changes them accordingly.
 
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I've sat at Bob's table at Oshkosh many times. He knows what he's doing. What I don't like is he tries to scare all who ask about their Stromberg. He'll tell you that it's not legal till he looks at it and determines it legal. Maybe so? These carbs have been built from parts carbs for years and still run just fine. If he got 3 or 4 hundred bucks I say send it to him but I think he's between 11 or $1200 now.
Get the manual and look at yours. If then your not comfortable then send it out

Glenn
 
Crash said:
When someone dedicates their entire business to rebuilding one specific brand and model of carb, has basically written the book on how they work and how to rebuild them, and has amassed a massive collection of every type of discontinued part out there, I think it's safe to say that person is the best at that niche.

In this case it's Bob and all he does is rebuild Stromberg NAS3 carbs. I'd say that qualifies him to be the "best" at it.

I'm not saying that's the absolute best option for every case as evidenced by how many Strombergs have been rebuilt by amateurs but if you have the money and want your Stromberg to be absolutely perfect and rebuilt 100% to original spec then the Stromberg Specialist is pretty much the only game in town.

I'd also like to remind that the original post was mentioning taking a C90 carb and converting it to a C85 set up carb. This is not a simple rebuild/tune but rather probably one that will need new jets purchased and the carb blueprinted against the C85 carb specs. Best to get a specialist to do it unless the OP is extremely detail oriented and checks all the orifice sizes and changes them accordingly.
Click to expand...


nope, hes probably good at it but theres a lot of others that are too.i will have to tell my guy hes a amateur. only difference between a 85 and a 90 is the jets and venturi that im aware of. 3 non moving parts. real simple to replace those 3 parts. orfice sizes just takes that size drill bit either it goes or dosent. only difference is most dont advertise there services he does, which is ok.
 
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I just had Don's Dream Machines repair mine. Excellent work, good price, and 4 day turn time.
Dave
 
tempdoug said:
.i will have to tell my guy hes a amateur
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Touchy crowd huh

Don't take it personal against "your guy". Not everyone has a guy who they trust to do carb work and for an unknown poster with 2 whole posts asking for suggestions on how to rebuild a carb and convert it from one configuration to another the safe bet is to point him (or her) to "THE GUY" who is widely known and easily available to work on a Stromberg. Plus sourcing the parts mentioned can be problematic unless "your guy" has a stash of Stromberg parts to pull from.
 
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Drip. Drip. Drip. Is there anyone on here that does not have a Champ or a Cub in a back hangar on their airport with gas stains down the cowling and a puddle on the floor because the owner forgot to turn the gas off? That stone simple Stromberg carburetor that was overhauled by a farmer at his kitchen table while watching Jeopardy needs another overhaul, the floats too high. Where is my can of Gumout? Or maybe there is a fuel bowl vent modification service bulletin that needs to be complied with. Your carb any your money. Drip. Drip. Drip.
 
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cruiser said:
Drip. Drip. Drip. Is there anyone on here that does not have a Champ or a Cub in a back hangar on their airport with gas stains down the cowling and a puddle on the floor because the owner forgot to turn the gas off? That stone simple Stromberg carburetor that was overhauled by a farmer at his kitchen table while watching Jeopardy needs another overhaul, the floats too high. Where is my can of Gumout? Or maybe there is a fuel bowl vent modification service bulletin that needs to be complied with. Your carb any your money. Drip. Drip. Drip.
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Ha, 15+ years ago I called Fresno Airmotive who had a guy who was a Bergh guru. I told him my stumbing problem and said I should mention that my carb didn't drip like all my friends carbs did. He said " when I get done helping you it will "

Glenn
 
Bob is not accepting carburetors because of Covid so that takes him out of the picture anyway. We have one on a J3 that Bob did his magic on. It never leaked before but does now and runs way to rich. It is on it's way to Aircraft Carburetor and Fuel Injection of Texas. I have always he=ad great service from them on everything from pressure carbs on the old Bonanzas, carbs on the Wright 3350 down to the little Stomberg.
 
I have both a steel needle/sharp edged seat and a delrin needle/rounded seat to try. Will try putting a vacuum to the inlet side and see which one holds pressure better.

A local carb/mag rebuilder up here told me to never lap a steel needle into a brass seat as the compound will embed itself into the brass and the seat will never seal right. Instead set the needle into the seat and give it a good whack with a hammer to set the needle into the seat. Something I might try.
 
the only 2 things to struggle with in those carbs is safety tying the main discharge nozzle and arm, ive got 5 thumbs on each hand and setting the float with no leaks, set some fuel up about 3 feet with a hose when doing it.
 
Crash said:
I have both a steel needle/sharp edged seat and a delrin needle/rounded seat to try. Will try putting a vacuum to the inlet side and see which one holds pressure better.

A local carb/mag rebuilder up here told me to never lap a steel needle into a brass seat as the compound will embed itself into the brass and the seat will never seal right. Instead set the needle into the seat and give it a good whack with a hammer to set the needle into the seat. Something I might try.
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They do make a lapping compound for soft metal. I have not tried it so advice is worth what you paid for it. https://ws2coating.com/2014/02/20/create-better-component-surface-finishes-with-lapping-compounds/
DENNY
 
Steve Pierce said:
Here is a file of Stromberg carburetor data that I have gathered over the years. I built a few out of a box of parts and had good service. There is some tribal knowledge for sure. https://drive.google.com/drive/folders/1xYSpK0qJCqNY8fq2JWITqRw0mda1AlVE?usp=sharing
Click to expand...

My C-85 has a real flat spot between 1200-1500. If you don't run carb heat when cold on the ground (25-55'F) it likes to quit if you jab the throttle at all. I heard that richening the idle mixture helps. Otherwise it runs great. Any suggestions, other than don't jab the throttle?. (new needle and seat/low hours since overhaul)
 
WhiskeyMike said:
My C-85 has a real flat spot between 1200-1500. If you don't run carb heat when cold on the ground (25-55'F) it likes to quit if you jab the throttle at all. I heard that richening the idle mixture helps. Otherwise it runs great. Any suggestions, other than don't jab the throttle?. (new needle and seat/low hours since overhaul)
Click to expand...
If this just started happening in the cold weather, richen the idle mixture a turn.
 
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