Old Carb.

Tom-D

Tom-D

Taxi to Parking
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Feb 23, 2005
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Tom-D
what would you do with it?

it seems to run fine, no leaks.

but it is way old.
 

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Definitely need to run the entire list of SBs that cover that model carb, for every parts manufacturer, unless the logs show to be done. There are a number of them that are stacked on top of each other and several that supercede others and others that change compliance and requirements.

A quick look showed at least 3 dealing with the body bolts showing signs of leakage. All were issued by different companies, some with installation effectivites, some for parts installations and others for overhaul facilities. Then there are the float and venturi messes too.

The Marvel line of carbs has been made and sold as well as supported by a number of companies over the years, and it has become a very tangled web of data and inspection requirements.
 
Craig said:
Definitely need to run the entire list of SBs that cover that model carb, for every parts manufacturer, unless the logs show to be done. There are a number of them that are stacked on top of each other and several that supercede others and others that change compliance and requirements.

A quick look showed at least 3 dealing with the body bolts showing signs of leakage. All were issued by different companies, some with installation effectivites, some for parts installations and others for overhaul facilities. Then there are the float and venturi messes too.

The Marvel line of carbs has been made and sold as well as supported by a number of companies over the years, and it has become a very tangled web of data and inspection requirements.
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This carb shows that the ADs have been complied with (V) (F) stamped on the data plate & SBs aren't required.
 
This carb does have a discrepancy that should not pass annual.
 
With the history on the Marvels, anyone who doesn’t adhere to the SB’s is an idiot.
 
Craig said:
With the history on the Marvels, anyone who doesn’t adhere to the SB’s is an idiot.
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But the shade tree mechanics will try to tell the owners SB's aren't required, therefore don't do them. o_O:rolleyes:
 
Salty said:
And this is why answering any question you ask is a waste of everyone's time.
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It would be apparent for anyone familiar to the carb.. and it has nothing about SBs.
 
Craig said:
With the history on the Marvels, anyone who doesn’t adhere to the SB’s is an idiot.
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Do your home work!
Anyone who is familiar with carb would know why the AD on the Venturi occurred and why Precision Airmotive no longer makes the carb.
Do you know why the MA3SPA uses 1-2 gallons more fuel than the early unmodified carbs? and why that is not good.
 
Craig said:
With the history on the Marvels, anyone who doesn’t adhere to the SB’s is an idiot.
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when you adhere to all Service Bulletins or replace the carb with new, the carb is no longer able to run auto fuel?
read the tag provided with the replacement carb.
 
My airplane is 50 years old. By definition, the carb is as well and I know it has been overhauled at least once because I had it done a few annuals ago.
 
Tom-D said:
Do your home work!
Anyone who is familiar with carb would know why the AD on the Venturi occurred and why Precision Airmotive no longer makes the carb.
Do you know why the MA3SPA uses 1-2 gallons more fuel than the early unmodified carbs? and why that is not good.
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Can you please elaborate? My plane has the same carb, and while I'm aware of the venturi AD I don't know the history or the real world risk.
 
Dana said:
Can you please elaborate? My plane has the same carb, and while I'm aware of the venturi AD I don't know the history or the real world risk.
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The world of CARBs is a long story, there were several companies involved, Marvel invented the carb many years ago and was doing fine until Precision Airmotive got involved, they used 7carb failures in 37 years invoke a emergency AD to place a 1 piece Venturi, this screwed up the flow rate in the carb, and it would not run correctly. After 4 re-rites the AD was modified so the original parts could be re-installed and checked each 100 hours for looseness of the Venturi.
during the process we find the parts were being manufacturing by Kelly they finally bought the mess and now have the rich mixture problem solved.
If you have a Yellow data tag on your carb it is one that KELLY made after the mess boiled out.
the carb pictured has no problem, it runs great. and the discrepancy I am talking has nothing to do with the ADs or SBs.
OBTW,,, I do not inspect or maintain this Carb/Aircraft. I spotted the discrepancy while helping un-cowling.
 
the discrepancy is wrong parts installed.
can you see them?
 

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So, this is one of those "everything works perfectly well, but the airplane is not 'airworthy' because it does not exactly match what was written on a piece of paper in 1948" situations. And, you can't get what was written in 1948 because the part with the correct part number hasn't been produced for the last 70 years.

And people wonder why aviation is dying.
 
Capt. Geoffrey Thorpe said:
So, this is one of those "everything works perfectly well, but the airplane is not 'airworthy' because it does not exactly match what was written on a piece of paper in 1948" situations. And, you can't get what was written in 1948 because the part with the correct part number hasn't been produced for the last 70 years.
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pretty much, but when the aircraft is not assembled properly isn't that a discrepancy that should corrected?
When Continental requires a positive stoped nut shouldn't there a cotter key?
the 4 studs that hold the carb to the sump provide the cotter key hole, shouldn't they used?
 
I see several differences from this one:

upload_2020-9-24_20-51-17.png
 
Lycoming long ago started using plain nuts, lockwashers and flat washers to mount their carbs. Studs weren't drilled.
 
Dan Thomas said:
Lycoming long ago started using plain nuts, lockwashers and flat washers to mount their carbs. Studs weren't drilled.
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I'm not your Lycoming Guy. It's interesting.
 
Tom-D said:
pretty much, but when the aircraft is not assembled properly isn't that a discrepancy that should corrected?
When Continental requires a positive stoped nut shouldn't there a cotter key?
the 4 studs that hold the carb to the sump provide the cotter key hole, shouldn't they used?
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Depends on the installation. The current small Continental parts book shows a plain washer, lock washer and plain nut. Maybe in a previous version it was to be safety wired, but times do change. In the picture I didn't see an exposed cotter pin hole in the studs. Maybe Continental was having studs break in service, and changed to a solid stud. Might be a service bulletin on that.
 
JAWS said:
Depends on the installation. The current small Continental parts book shows a plain washer, lock washer and plain nut. Maybe in a previous version it was to be safety wired, but times do change. In the picture I didn't see an exposed cotter pin hole in the studs. Maybe Continental was having studs break in service, and changed to a solid stud. Might be a service bulletin on that.
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The 0-300- shown here requires a castle nut and cotter key. not a MS210--- style in the picture.
You are correct the IBP should be followed.
 
JAWS said:
Depends on the installation. The current small Continental parts book shows a plain washer, lock washer and plain nut.
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Which small continental ? the 0-200/A-65/85/90 requires it to be located on the intake spider and a stat-o-seal separating the case and intake then a washer then a castle nut and key.
http://rob.com/matt/manuals/O-200_Parts_manual.pdf

this publication shows a tilison carb - washer and nut.

correction..
http://nctc.tk/Continenl/Parts Catalogs/C-125, C-145 & 0-300.pdf

Fig. 13 Item 17 & 18 also shows a flat washer with nut

Ya learn some thing every day. wonder why the stud shows a hole for a cotter key.
 
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From the O200 reference above, the carb is attached with items 23, 24, 25, figure 12. They fit the carb to the studs, item 6. The carb attaches to the manifold.

The intake manifold (spider) is attached with items 1, 2, 3, 4, figure 12. The studs for the spider are not shown in figure 12. You have to go to figure 1, I think item 11. It is the manifold that requires castellated nuts and cotter pins, due to the lock seals that seal it - don't want to crush the seal with too much torque and allow the seals to shrink and expand.
 
JAWS said:
The intake manifold (spider) is attached with items 1, 2, 3, 4, figure 12. The studs for the spider are not shown in figure 12. You have to go to figure 1, I think item 11. It is the manifold that requires castellated nuts and cotter pins, due to the lock seals that seal it - don't want to crush the seal with too much torque and allow the seals to shrink and expand.
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Those Lock-O-Seals aren't sealing anything. They're acting as flexible washers to allow the manifold to rock a little on the studs. The Marvel Schebler carb has a bad habit of sloshing fuel out the bowl vent, which is in the carb bore behind the venturi, causing flooding and rough running. The weight of the carb and the torsional vibration of the O-200 worked together to make that carb do that at certain RPMs. Rough running and serious RPM drops can happen.

The overhaul manual has an innocuous little paragraph about tightening those castellated nuts. You run them up finger tight and then to the first notch that lines up with the cotter pin hole in the stud and install the cotter pin. NO wrench is used. They want that manifold flexible, and the rubber connectors on the induction tubes will allow some movement. I spent a couple of weeks troubleshooting an unhappy O-200 in a 150 20+ years ago and finally read the stupid instructions. Did what they told me and the engine smartened right up. I found that the rebuilder had left the Lock-O-Seals out altogether and had the manifold rigid, and have found several others like that, too.
 
Dan Thomas said:
T

The overhaul manual has an innocuous little paragraph about tightening those castellated nuts. You run them up finger tight and then to the first notch that lines up with the cotter pin hole in the stud and install the cotter pin. NO wrench is used. They want that manifold flexible, and the rubber connectors on the induction tubes will allow some movement. I spent a couple of weeks troubleshooting an unhappy O-200 in a 150 20+ years ago and finally read the stupid instructions. Did what they told me and the engine smartened right up. I found that the rebuilder had left the Lock-O-Seals out altogether and had the manifold rigid, and have found several others like that, too.
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been there too, but the 0-300 doesn't have that problem. when the 4 studs have key holes, use cotter keys.
 
Dan Thomas said:
Those Lock-O-Seals aren't sealing anything. They're acting as flexible washers to allow the manifold to rock a little on the studs. The Marvel Schebler carb has a bad habit of sloshing fuel out the bowl vent, which is in the carb bore behind the venturi, causing flooding and rough running. The weight of the carb and the torsional vibration of the O-200 worked together to make that carb do that at certain RPMs. Rough running and serious RPM drops can happen.

The overhaul manual has an innocuous little paragraph about tightening those castellated nuts. You run them up finger tight and then to the first notch that lines up with the cotter pin hole in the stud and install the cotter pin. NO wrench is used. They want that manifold flexible, and the rubber connectors on the induction tubes will allow some movement. I spent a couple of weeks troubleshooting an unhappy O-200 in a 150 20+ years ago and finally read the stupid instructions. Did what they told me and the engine smartened right up. I found that the rebuilder had left the Lock-O-Seals out altogether and had the manifold rigid, and have found several others like that, too.
Click to expand...

Cool. I thought they sealed the spider. Learn something new everyday. I helped a guy over the phone with his 150 a long while ago with carb issues on climb out. I wonder if this was the fix? I never did hear back from him.
 
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