The International Cessna^® 170 Association

I decided that want to do a full check overhaul of my carburetor Marvel MA3SPA my engine is not running perfectly smooth and after spent a lot of time and $ trying to find the problem decided to overhaul mags and carb (previous owner didn't fly the airplane much), anybody can recomend me a good shop to send my carburettor? I am based in Livermore CA, Thanks.

WHEN...does it not run perfectly smooth? Takeoff power? ...could be weak valve springs. (When were your cylinders overhauled?...and were the valve springs checked?...or were they simply re-used...?

Confirm that you have the correct carburetor for your engine. Many MA-3 carbs will fit and just because you bought it that way doesn't mean that's what should be on it. (The C-125 engine carb was a 10-2848, but the C-145/O-300 was 10-4439. The specific differences escape me just now, but it still makes sense to confirm the datatag.)

My favorite carb overhaul shop was Hatfield in Houston, however Bill Hatfield has passed away and left the shop to his employees.
I have not had a carb overhauled by them, but they are the long time guys who did it for Bill.
Hatfield Aviation
Address: 8109 Braniff Street, Houston, TX 77061
Phone:(713) 644-1464

My second choice was Consolodated but they've retired from the business. I've heard poor performance stories from Tempest/Volare and would prefer an independent shop who has a proper flow-bench....

Airmotive Carburetor Co
475-479 Riverside Dr
Burbank, CA 91506 USA
Tel: 818-845-7455

Aircraft Fuel Injection Service Inc
2731 Brookfield St
Dallas, TX 75235 USA
Tel: 214-358-2377

but...

Here is the direct-link to the carburetor manufacturer, who will overhaul it for you: http://msacarbs.com/

From Terry Welshans History of Aircraft Carburetors:
"Great improvements in mixture control came about after 1920. This was due in part to advances made in engineering and chemistry and in the improvements in higher education. The gains made were in parallel with the aircraft and automotive requirements, which were performance driven by the publicity and popularity of racing. Recall that James Allison was motivated to get the maximum performance possible at the Indianapolis speedway, a hobby that eventually led to the development of the Allison aircraft engine. In 1904, Harry C. Stutz, who was involved in the design and manufacture of internal combustion engines, introduced George Schebler to Frank W. Wheeler. In the resulting partnership, Wheeler provided the money, while Schebler provided engineering skills. Stutz worked temporarily as Sales Manager. By 1907, they had achieved enough success to move to Indianapolis into a state-of-the-art building, a plant that reportedly was one of the most advanced manufacturing facilities in the United States at the time. Frank Wheeler and three other local men (including James Allison) opened the Indianapolis Motor Speedway in 1909. Prior to the inauguration of the Indianapolis 500 in 1911, the Wheeler-Schebler company sponsored the Wheeler-Schebler Trophy Race at the track. George Schebler sold his interests in the company in 1912, but it continued to operate under the Wheeler-Schebler name until 1928, when it evolved into the Marvel-Schebler Carburetor Company, one of five companies that played a role in the development of what that would become the Borg-Warner Corporation. The factory produced carburetors from 1911 up to 1951. Indianapolis 500 winners receives the Borg-Warner Trophy to this day.
....
"Originally known as the Wheeler-Schebler carburetor company, it became Marvel-Schebler Carburetor Company when it merged with Marvel Carburetor Company. The Marvel-Schebler company did some early work connected with developing fuel-injection systems in the late 1950s and early 60s, eventually merging with the Borg Warner owned Tillotson Carburetor Company in 1971. In 1985, parent company Borg Warner changed the division name to "Control Systems." Borg-Warner went through a leveraged buyout in 1987, spinning off the Borg Warner Automotive Inc., as an independent company that is still in operation, developing fuel-efficient engine and drive train technology. Marvel-Schebler/Tillotson spun away from Borg-Warner to become Facet Aerospace Products Company, which first became Precision Airmotive Corporation, then Volare Carburetors LLC, then Marvel-Schebler® Aircraft Carburetors (MSA). MSA produces these carburetors under Aero Accessories, Inc’s (Aero) FAA - PMA authorization. Marvel-Schebler® produces models: MA-3A™, MA-3PA™, MA-3SPA™, MA-4SPA™, MA-4-5™, MA-4-5AA™, MA-6AA™, and HA-6™. Continental, Lycoming and Franklin four- and six-cylinder horizontally-opposed aircraft engines use these carburetors"

http://www.enginehistory.org/Accessorie ... Hx01.shtml

I was very happy with exchanging my last carburetor at Chief Aircraft. Same with the mags. But that WAS 9 years ago...

A little closer to Livermore is Ly-con Rebuilding Co 8231 W Doe Ave, Visalia, CA 93291 559 651 1070. Ask for Chris. They do carbs, mags, and cylinders. Excellent reputation for engine overhaul/repair as well.

voorheesh wrote:A little closer to Livermore is Ly-con Rebuilding Co 8231 W Doe Ave, Visalia, CA 93291 559 651 1070. Ask for Chris. They do carbs, mags, and cylinders. Excellent reputation for engine overhaul/repair as well.

Good advice Ly Con overhauled this engine for the previous owner in 97.

correamoon wrote:

voorheesh wrote:A little closer to Livermore is Ly-con Rebuilding Co 8231 W Doe Ave, Visalia, CA 93291 559 651 1070. Ask for Chris. They do carbs, mags, and cylinders. Excellent reputation for engine overhaul/repair as well.

Good advice Ly Con overhauled this engine for the previous owner in 97.

They are a reputable shop and that probably answers the valve spring question. (But, last I heard they sent out accy overhaul work such as carbs, gens, starters, etc..)

gahorn wrote:WHEN...does it not run perfectly smooth? Takeoff power? ...could be weak valve springs. (When were your cylinders overhauled?...and were the valve springs checked?...or were they simply re-used...?

Confirm that you have the correct carburetor for your engine. Many MA-3 carbs will fit and just because you bought it that way doesn't mean that's what should be on it. (The C-125 engine carb was a 10-2848, but the C-145/O-300 was 10-4439. The specific differences escape me just now, but it still makes sense to confirm the datatag.)

Dear Gahorn

You just opened the Pandora box...well let's start from the beginning (: ...I am Leonardo from Uruguay, living in China for the past 6 years flying an Airbus for a Chinese carrier (yeah computer operator...dangerous computer..), in 2013 I fulfilled a dream, Oshkosh! comeback to China like crazy wanting to fly real airplanes again...well GA is forbidden in China...so I chill out and went to OSH again in 2014...well in OSH having some beers with my friend Allan Miller who also punches buttons on an A330 but owns a couple of Champs and flies a B-25 on his free days (you get the picture eh..) we started to talk about what I could buy...he asked what you want? I said taildragger! (used to fly them a long time ago...) he said ok...how many seats? I said eh 2...but wife and daughter mmmm...ok 4...well the talk ended with a list of candidates with the C170 as highly recommended...well back in China with a lot of time in hotels between flights and a good bank account I ended buying a C170 in Sacramento CA....(wait don't fall from the chair there was a pre purchase inspection...)

Ok Chapter 2...the C170 looked super solid, same family for 20 years, based in Sacramento in hangar...bad side average flight time around 20 hours a year since 1997...well I found a mechanic in Livermore and he did the pre purchase and give me thumbs up and a go ahead...Ok I transfer the money schedule a holiday including Disneyland for my daughter and we flew from China to Sacramento (this is the super short version of the story not everything was that smooth..)...well as I didn't have a FAA license in that moment I also arranged a ferry pilot for the short flight from Sacramento to Livermore were I found a hangar, original plan was to leave it there a few months and then fly it coast to coast to Florida to be shipped to Uruguay but fall in love with CA and now my airplane is a permanent resident in Livermore and I go there on holidays, ok back on track...we did the ferry flight and also some flight around SF and that was my last day free and airplane went to the hangar waiting for me to comeback...

Well the ferry pilot super cool guy John Quayle a resident of Livermore, very experienced pilot and mechanic ex C170 owner told me your engine is running rough something is not right...Ok...I didn't have any experience with this engines always flew 4 cylinders engines before enter the airlines 20 years ago so for me was ok...didn't know this 6 cylinders are super smooth (now I know...)...well I contacted the mechanic that did the pre purchase in Livermore and asked him to check for the problem I expected something simple and that the problem could be related to that the airplane was not flown very often...

Engine has 390 hours since overhaul by Ly Con in 1997 including carb and mags, carb has the single venturi and proper fuel nozzle (at least on the overhaul papers, called Marvel to check the parts list that was changed by Ly Con and all are correct)

Ok a lot of $$$ later and 4 mechanics my engine is still running "sometimes" rough, I went on holidays last month stayed 2 weeks in Livermore, flew 30 hours got my FAA license, tail dragger endorsement and spent a lot of time in the hangar with mechanics, overall very cool experience except that still runs rough...here goes the symptoms...

Engine does full power, 2350 RPM on take off with cruise prop.
Sometimes runs a little rough sometimes not and not any specific range, sometimes after start, sometimes climbing, etc..
Usually when you lean runs smoother so we thought was too rich...called the previous owner and he told me that he always flew it like that...just lean it...after lean it usually runs smoother.

What we checked:

Plugs, changed (and new ones pressure checked)
Harness, checked.
Mags, checked Left one looks slightly weak, we found a suspicious points and we changed them, the rest looks like new and timing checked)

Primer checked and seals changed anyways, no leak.
Manifold instrument line, we tapped the line and after that the engine ran smooth! we thought we found a the problem...wrong...later the problem was back)

Valves...reamed and new springs, we found a lifter collapsed changed but was not the problem.

Prop, in proper track and feels slightly out of balance but we are sure is not the problem, a dynamic balance coming soon.

We found the connecting rod pin of one of the cylinders with too much movement, I changed the cylinder.

Cam lob checked on at least 2 cylinders like new, no metal in 2 oil changes.

I don't think is the counter balance of the crankshaft.

Heater box not perfect but good enough according the mechanic.

Intake manifold rubbers changed.

Carb visually checked, float in good condition and proper adjustment.

Well as you can see mostly everything has been checked...really frustrating issue at this point the possibilities are that the problem is intermittent so is in one of the components already checked and the mechanic miss it or I don't know...the airplane is in great overall condition always taken good care by previous owner, several C170 owners that saw it said you have a great solid airplane but somehow we can't find the issue so I will get more aggressive sending the mags to overhaul and carb I expect there is something small somewhere that is screwing up the mixture in an intermittent way and that is why nobody can find it...

Leonardo

Congratulations on your new airplane and it sounds like you are taking all the right steps in getting checked out and making sure it is airworthy. It is normal for these engines to run slightly rough after start but they should run smooth within a minute or so. Prop imbalance manifest more as a vibration or slight shaking as opposed to engine roughness. Your mechanic has probably checked but make sure when you move the mixture to idle cut off that the rpm rises slightly before cutoff indicating mixture control adjusted properly. Roughness in flight or during ground ops might be the result of carb ice and this is a common problem in California where it is so dry that pilots are lulled into complacency until it sneaks up on them. Experts will tell you: "impossible" If it ices up it will be obvious and will quit unless you apply carb heat. I have heard of cases involving intermittent carb ice including occasional roughness. You might try applying carb heat when you experience roughness and see if that helps. Some old-timers will tell you that partial carb heat can help smooth engine roughness under these circumstances. (carb ice can occur up to 70 degrees plus with sufficient moisture in atmosphere) Chris at Lycon told me they have a bench in house to perform work on these carbs.

Leonardo,
When you do get around to having your prop dynamically balanced be sure to check that it is clocked properly before starting the balance procedure. The prop should be 11 o-clock to 5 o-clock position with the number one cylinder at top-dead-center. It would be a good idea to check the prop position regardless of weather you balance it or not.

johneeb wrote:Leonardo,
When you do get around to having your prop dynamically balanced be sure to check that it is clocked properly before starting the balance procedure. The prop should be 11 o-clock to 5 o-clock position with the number one cylinder at top-dead-center. It would be a good idea to check the prop position regardless of weather you balance it or not.

That position is performed facing aft as if to hand prop the engine.

voorheesh wrote:Congratulations on your new airplane and it sounds like you are taking all the right steps in getting checked out and making sure it is airworthy. It is normal for these engines to run slightly rough after start but they should run smooth within a minute or so. Prop imbalance manifest more as a vibration or slight shaking as opposed to engine roughness. Your mechanic has probably checked but make sure when you move the mixture to idle cut off that the rpm rises slightly before cutoff indicating mixture control adjusted properly. Roughness in flight or during ground ops might be the result of carb ice and this is a common problem in California where it is so dry that pilots are lulled into complacency until it sneaks up on them. Experts will tell you: "impossible" If it ices up it will be obvious and will quit unless you apply carb heat. I have heard of cases involving intermittent carb ice including occasional roughness. You might try applying carb heat when you experience roughness and see if that helps. Some old-timers will tell you that partial carb heat can help smooth engine roughness under these circumstances. (carb ice can occur up to 70 degrees plus with sufficient moisture in atmosphere) Chris at Lycon told me they have a bench in house to perform work on these carbs.

You bring an interesting point as my carb temperature indicator shows low temperatures too often...and I respect them and use carb heat all the time even immediately after take off, according two very experience pilots/mechanics my temperature indicator could be working wrong but on the ground before flight is showing the right ambient temperature...is anything that can be wrong in the carburettor that can be creating more ice than it should?

The prop position was checked and adjusted, the balance was checked just by hanging the prop and marking the position when rotated I know is not the best way but was the only one we had and looks good but I can feel is not perfect as you can feel and slight increase in vibration when turning right, which is not the same of the roughness.

I do get the 50 RPM increase when cutting the mixture but as I said the problem is intermittent.

Good thing about this problem is I am learning a lot, also all mechanics agree that is a very solid engine and the roughness must be something minor that nobody could find so far...

Thanks for all the comments.

I am not aware of any fault in the carb itself that would make it more susceptible to ice. Maybe someone else? Your induction system might be worth checking to make sure your carb heat is rigged/functioning properly. With all the attention your aircraft has received, I would be surprised if that was an issue. If your intermittent problem is present on our really dry days, it probably is not carb ice. I would definitely get with Lycon on this issue since they overhauled your engine, even though it was awhile ago. They are known to stand behind their work and the family has a good maintenance shop at Visalia Airport that could assist you in getting to the bottom of this problem also. The engine rebuilding shop is about a mile from the airport. Good luck.

My first thought was sticking valves, a common problem discussed here. But as you've checked the valves that can probably be ruled out. It would be helpful to have a CHT/EGT probes on all six cylinders to see if the roughness could be isolated to one cylinder. To another owner with a rough running engine George gave this advice:

gahorn wrote:There's a baffle above the carburetor that in some engines is rivetted and has been known to shake loose and block one of the "spiders" ...or intake pathways. You'll have to remove the carburetor to check for that. I recommend you first do the compression test, then the rocker-cover removal observation, then the carb removal to check the intake baffle.

The three things I remember that cause mild roughness in these engines are:

1) The clocking of the propeller, mentioned before

2) Loose intake manifold hoses or elbows. A small leak in an intake connection will cause that cylinder to run lean.

3) Broken flow divider in the sump just above the carburetor. The newer sumps have this part cast in as part of the sump and have no problems. The older ones were made out of sheet steel and riveted (this may not be the right word, but the fastener is similar to those attaching the data plate) and had a tendency to crack and fall out or get sucked up higher into the intake system, causing uneven mixture distribution. Check the third post in this thread for photos. Edit: Sorry George, I missed your post on this possibility before I posted. At least now there's a link to the photos...)

correamoon wrote:[...
You bring an interesting point as my carb temperature indicator shows low temperatures too often...and I respect them and use carb heat all the time even immediately after take off, according two very experience pilots/mechanics my temperature indicator could be working wrong but on the ground before flight is showing the right ambient temperature...is anything that can be wrong in the carburettor that can be creating more ice than it should?....

A lower temp than ambient during engine operation is quite normal. The method to use a carb temp gauge is to avoid carb throat temps below abotu 35 degrees F (5C). The vaporizing fuel refrigerates the carb throat and freezing temps may cause humidity to freeze and reduce air flow. It is highly unlikely you need carb heat at full throttle climb after takeoff.

I also had an occasional rough engine about ten years ago which was traced to leaking oil seals in my magnetos. It was intermittent and virtually impossible to duplicate. Slight oily-ness inside the points cavity ws cured with new seals and no more problem.