Steel Needle Stromberg Carburetor

[flyken]

Re: Steel Needle Stromberg Carburetor

Regarding the Stromberg carb, the reason why many have the mixture control either removed or tied off is because dirt/debris gets in there causing the diameter of the holes to be smaller so less fuel passes thru and you end up with a lean mixture and cooking your cylinders. As for the Marvel, now Precision carburator being over rich well no it is not. It is indeed a precision carb and you use the mixture control (with your egt and/or cht) to precisely mix the fuel/air. You actually will burn less fuel with a precision carb provided you lean properly - and you can generally start leaning above 2500ft asl in normal atmospheric conditions in level flight on the smaller continental engines. The 2nd great advantage to the precision carb is by properly leaning you are controlling cylinder head temps in climb, cruise and descent something you cannot do with a stromberg. This means longer periods between top overhauls and lower oil consumption. The 3rd great advantage to the precision carb is it has an accelerator pump and what this means is you don't run out of fuel when you suddenly need to add power on short final or when you find you have landed on soft groudn or overflow. The stromberg carb basically acts like a toilet bowl and as we all know once you flush the bowl you have to wait for the tank to refill with fluid. By having the accelerator pump there is no delay after advancing the throttle with a precision carb.

[Ragwing nut]

Re: Steel Needle Stromberg Carburetor

On the tail wheel mod, besides the bleed air port change, there is also a slightly lower float setting. Steel needles won't leak once properly seats. Most the time the needle seat is wore out and won't properly lap.

[N96337]

Re: Steel Needle Stromberg Carburetor

Regarding the Stromberg carb, the reason why many have the mixture control either removed or tied off is because dirt/debris gets in there causing the diameter of the holes to be smaller so less fuel passes thru and you end up with a lean mixture and cooking your cylinders. As for the Marvel, now Precision carburator being over rich well no it is not. It is indeed a precision carb and you use the mixture control (with your egt and/or cht) to precisely mix the fuel/air. You actually will burn less fuel with a precision carb provided you lean properly - and you can generally start leaning above 2500ft asl in normal atmospheric conditions in level flight on the smaller continental engines. The 2nd great advantage to the precision carb is by properly leaning you are controlling cylinder head temps in climb, cruise and descent something you cannot do with a stromberg. This means longer periods between top overhauls and lower oil consumption. The 3rd great advantage to the precision carb is it has an accelerator pump and what this means is you don't run out of fuel when you suddenly need to add power on short final or when you find you have landed on soft groudn or overflow. The stromberg carb basically acts like a toilet bowl and as we all know once you flush the bowl you have to wait for the tank to refill with fluid. By having the accelerator pump there is no delay after advancing the throttle with a precision carb.

Not quite true....but a common misconception all the way around.
The mixture control is of a "back suction" type. NO fuel flows through the orfices in the mixture plates...they only vary the amount of pressure on the fuel in the float chamber, thus leaning or enrichening the mixture. When the biggest holes in the upper and lower plates are aligned, the float chamber is subjected to basically atmospheric pressure, and when the smallest are aligned the pressure acting on the float chamber is subjected to less pressure. This is why you don't see the instant effect of leaning as you do on a direct mixture carburetor. These are extremely simple, but you can't compare apples to oranges.
The lack of an accelerator pump doesn't mean "once you flush the bowl you have to wait for the tank to refill with fluid"... what happens is the mixture goes too lean when you spike the throttle because of the now suddenly open position of the throttle plate and the engine wants to stutter. The same amount of fuel is still in the carburetor, so you don't have to "wait for the tank to refill with fluid". An accelerator pump just shoots a blast of fuel into the venturi to enrichen the mixture when you spike the throttle. Again, a not uncommon misconception, but not quite the way things work.
John

[flyken]

Re: Steel Needle Stromberg Carburetor

The stromberg misture disc has 4 apertures in it and they do get contricted from dirt etc and this causes a leaner mixture over time and that is why you end up overheating cylinders in climb or with trying to lean with a stromberg. Without the suction of the airflow you don't get the fuel. The toilet bowl in the stromberg only holds so much fuel and can only release that fuel at a limited rate. The precision with the accelerator pump delivers more fuel - or if you prefer provides more pressure the end result is the same. The precision carb will make your engine perform more economically, with more cylinder temperature control, and smoother power changes.

[flyken]

Re: Steel Needle Stromberg Carburetor

I should add I am sorry if I was bad with my stromberg carb principles its been a long time since I dealt with one - and it mostly brings up unpleasant memories. I once built a vacuum tube radio but would be hard pressed to explain how that works now too. Maybe its best to forget and buy an Icom. The precision to me is clearly a better product that saves you money in the long run on fuel as well as prolonging cylinder life. I am not trying to upset Stromberg lovers but sometimes it is better to go with newer technology. I've also thrown out my phonograph, 8-track, tape recorder, phonograph and Narco Com11A. I've kept the woodstove.

[Joel Severinghaus]

Re: Steel Needle Stromberg Carburetor

Aircraft Systems is still there. They still do great work. George

I'll second that. Aircraft Systems in Rockford, IL overhauled my carburetor about a year ago (crack in the float was causing a fuel leak). Got the taildragger modification, Delrin needle, been very happy with it.

I've had Delrin bagpipe chanters, so I was already partial to that plastic.

[Frank DeBartolo]

Re: Steel Needle Stromberg Carburetor

God--I miss the 8 track tapes--or was it the times?

Frank D
N43684

[Larry Lyons]

Re: Steel Needle Stromberg Carburetor

Well sorry for switching subjects but! I had an 8-track in a 1964 Chevy van. Called her the blue whale, she had bunk beds, a surf board rack and we slept in her on the beach to catch the early tide. This was in the days before conversion vans. Old memories.............Larry

[flyguy]

Re: Steel Needle Stromberg Carburetor

Just one oops there.
The small holes in the slider do not affect the mixture when the control is set to full rich. They are sealed off and only the largest hole on the top rotating plate is aligned with the large hole in the bottom static plate. Dirt in the small holes would affect your ability to lean smoothly when the small holes were in use at very lean settings.
Just trying to keep it accurate for people with less experience.
Darryl

[NY86]

Re: Steel Needle Stromberg Carburetor

Blocked mixture control holes won't damage the engine. Furthermore, the amount of air flowing through the mixture plates is minimal and only while the control is being manipulated. In cruise no air flows in or out of the mixture control. And, if you get a blockage in the large holes you've got other problems already. To get an over lean condition, even if the holes are blocked, the pilot still has to over lean it . If you don't lean it it stays full rich. (Whether or not you can damage the engine this way is another argument for another day...)

The Stromberg doesn't suffer from a lack of an accelerator pump. It doesn't need one. It uses a different strategy and it works fine as long as you aren't using it as a stop light racer. And you'll never need to buy a $75.00 accelerator pump plunger, and said plunger will never sieze up and jam the throttle.

The reason the mixture often seems ineffective is the carb has already compensated for the change in altitude due to clever design. No other explanation makes sense. If you pulled the mixture control back on the Marvel and didn't get an RPM increase would you think it was junk, or would you think leaning was not called for?

The reason so many are wired rich is because student pilots had a habit of pulling it, thinking it was carb heat, or cabin heat, or whatever, and killing the engine, much to the consternation of the instructor.

I don't want to start a pissing contest, but everyone I meet who thinks the Stromberg is an inferior carb doesn't understand how it works or how to properly operate it. Simplicity is elegance.

The most current version of the Stromberg articles, written by my most excellent friend Neal Wright, can be found here.

[flyken]

Re: Steel Needle Stromberg Carburetor

A lean mixture will damage the engine and yes blocked holes will do it. The Stromberg does the job the Precision does it better. I flew with a Stromberg for years. When it started giving me problems, rather than putting too much money and time into keepiing it going, I went to the newer technology. I've found the Precision carb gives better performance particularly in cold weather, saves gas and controls cylinder head temps better. I can climb longer without overheating the cylinders and can control cooling of cylinders on descent better. Frankly I 've never met anyone who has flown both who prefers the Stromberg over the Precision but to each his own.

[N96337]

Re: Steel Needle Stromberg Carburetor

Flyguy & NY86, well said....I was going to reply, but could see there wasn't much use. John you're right..flow through those holes is very minimal... not like it's a metering jet. I've got some diagrams and stuff here...maybe I should scan them and start a new thread to try to explain the operation. I totally agree that those who complain about it, 99% of the time just don't understand how it works. Everyone looks for instantaneous change, and don't understand that it's not that type of system, and have no idea that there's already a bit of an automatic compensation system built in. Most of them are amazed when it's explained properly. I've flown both...and still have the Stromberg on my plane and every small engined airplane here that I take care of....why would I want to spend a pile of money for a different carb? These work well, are very simple and easy to maintain, do what they're designed to, and are already there. One Taylorcraft here in the valley has been owned by the same guy since new..and still has the Stromberg... and trust me, he's flown plenty of others. They aren't "old" technology... direct reaction carbs were in place before them.... it's mostly knowing how they work.
John

[Ragwing nut]

Re: Steel Needle Stromberg Carburetor

They are both ancient technology. On a small continental, a marvel on a 65 or 85 with accelerator pump is very rare to find even if there is a correct p/n for it, don't remember.

I run strombergs when I can simply based on the fact it costs me as a mechanic less than $50 in parts to overhaul, and I have plenty on the shelf to keep me flying. Marvels kits are 10x as much and I quit messing with them years ago simply because they would overhaul them for a few pennies more than it cost for the kit and I got a warranty with it.

[NY86]

Re: Steel Needle Stromberg Carburetor

The Stromberg does the job the Precision does it better.

Then why do you have to lean the Marvel and not the Stromberg?
Not my idea of "better".

[flyken]

Re: Steel Needle Stromberg Carburetor

Well again, you lean to save on gas - giving you more range - and to better control cylinder temp. By controlling cyl temp you prolong cylinder life. I knew Stromberg lovers would give me a hard time about this. The Precision yes is also at this point old technology. Again the most important reason for the switch to Precision is performance. When it is -20 at the surface and about 0 to -10 celcius aloft (inversion) and you are landing in deep snow or worse yet discover overflow that lag in acceleration is critical. Now instead of just slowing down a bit but being able to accelerate out you are stopped and stuck and will have a great time moving a bunch of snow and dragging your plane around. I should add the change in engine noise and performance flying thru an inversion is neat. Also when you are slipping into short strips with obstacles at the ends (meaning dead air)that bit of lag on short final can be critical. If you fly into high lakes on windy days you need all the help you can get. I like the way the Tcraft flies - I've Cubs and C180s and Beavers and Beech 18s(they fly nice too). I am not flying the edge more than I am comfortable with but I do sometimes ask alot of my Taylorcraft - but not more than it or I can do. The precision carb makes it a slightly better plane.