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PA-11, C-90 & Marvel vs Stromberg

George

George

Registered User
Huntsville, AL
For the PA-11 with a C-90-8F TCDS A-691 sez "(Bendix-Stromberg carburetor, Continental Part No. 530726 ... are required with this engine.)

1) Do I need the correct Part Number or can I just configure any NA-S3A1 for the C-90 (1-3/8" venturi, #46 jet, and #60 bleed air).

2) Can a Marvel intake be used on the Stromberg in a PA-11?

3) Also, why did the FAA limit the C-90 to the Stromberg when only installed on the PA-11.
 
Since no one else has jumped in here, I'll take a stab at it. I'd say that legally you'd have to install that exact part number for "just a logbook signoff". Any other Stromberg part number would require a Field Approval (337) This seems pretty simple, but I don't know in this day and age with the FAA.

Not sure what you mean by a Marvel intake.

It wasn't the FAA's fault. It was Piper that only tested the PA-11 with the Stromberg. Probably had something to do with the fact that it was what Piper was using on all(?) their other models at the time. Additions to the TC are usually driven by popular demand for an option while the aircraft is still in production. I believe the PA11 was in production for less than 2 years?

I'd first look and see if there is an STC for a Marvel carb on a PA11 and work from that. If there is no STC, you could go the Field Approval route. I don't think it would be too hard, but the FAA is funny nowadays.

Good luck!

John Scott
 
I searched for a STC but no joy. It would be simpler to just install the Stromberg though I would prefer the Marvel with the accelerator pump.

Marvel intake ... What I meant to ask was: other than the carberator does anything else need to be changed?

I just bought a PA-11 so I am on the steep end of the learning curve.

By the way this is a great site for information.

George
 
The Stromberg works just fine, though perhaps not as fuel efficient as the Marvel. That plus you better remember to turn the fuel off when the engine isn't running as it has a tendency to dribble out the carb.

I've had no problem with stuble or hesitation. I have noticed an rpm drop in a negative g situation when really agressively pushing over, but that's about it. Some mechanics love the Stromberg, others hate it. It is a very basic carb and simple to overhaul.

I'd love to know why it is the only one approved. I think John is probably right, although one knowledgeable IA I know says it had something to do with the effect of the pressure cowl on the Marvel intake, or something like that. Perhaps Clyde Smith knows the answer?

One thing is for sure, the PA-11 is a joy to fly. Problem is it grew up to be a Super Cub too soon!! :p
 
I'd use the Type Certificate Data Sheet for the C90 as approved data for a field approval to install the Marvel Schebler carb. It is approved on the engine. I doubt the was a MS carb for it then. That is why MS carbs are like hens teeth for C85s. They all came with Strombergs and everyone wants an MS but there weren't that many built. If anybody has a carb for a C85 I am looking for one to finish a project. Good O-200 carb core would work also.
 
Its a double whammy - Not only does A-691 exlcude the Marvel but TCDS E-252 for the C-90 says "NAS-3A1 (sic) carburetor P/N 530726, eligible only on Piper PA-11 airplanes equipped with Piper mufflers."

Enough have chimmed in to know that if there was an STC or 337 "For the installation of a C-90-8F with a MA-3SPA carburetor on a PA-11 ..." there would be one. Anybody A&Ps/IAs want to take a stab at it? Mine doesn't.

Off topic: A friend just swapped me a Stromberg core with the 1 3/8 venturi ... now I just need to find a #46 jet. But thats another thread.

George
 
From the PA11 TCDS
(5) C-90-8F (with propeller Item 5, 6, 7, 9, or 101) Use actual weight change
(Bendix-Stromberg carburetor, Continental Part No.
530726 and engine cooling baffles per Piper Dwg.
11258 Change E are required with this engine.)
Click to expand...

From the C90 TCDS
NOTE 5. Bendix-Stromberg NAS-341 carburetor, P/N 530726, eligible only on
Piper PA-11 airplanes equipped with Piper mufflers.
Click to expand...

I read that as saying you can only use the NAS-341 carb on the PA11 not another aiframe. I think this is doable through my PMI. Where are you located?

PA18 TCDS
Models PA-18 and PA-19:
Continental C-90-12F or C-90-8F (Uses carburetor setting No. 530726)
Click to expand...


People who have helped me with parts and service onStromberg carbs.
El Reno Aviation 800-521-0333 Ted is good on Stromberg carbs.
Airomotive Carburetor Co. 818-845-7455 Burbank CA also.
 
I'm in Huntsville, AL ... I've updated my profile.

I see you're in Texas. I'd be curious to find out what your PMI thinks. This may be worth a try if he thinks it is OK. At worst I just use a Stromberg and be done with it.

El Reno ... good guys. I used them for O-235 parts in my Colt I just sold.
 
Hmmm, perhaps I spoke too soon.

The other day on takeoff my engine was putting up a bit of a fuss. It was cold out (+7 C) and I had no preheat and warmed up for about 15 minutes prior to takeoff. The winter kit is on the front (except the airbox block).

It sputtered and developed only about 2250 until about a minute after takeoff when I throttled back and then forward again and it cranked right up to 2525. I had no problem for the rest of the day.

Now, I know from past experience that the C-90 really likes to be warm before the throttle is advanced, but when it ran up ok to 1700 I figured I was ok... :oops:

So, next time--preheat. Now, I've only turned my "big screw" adjustment on the back of the good old Stromberg carb out another quarter of a turn for increased richness in cold, dense air. Me thinks I need to turn it out a bit more....

Thoughts?
 
I would think the throttle pump of a Marvel would be nice under those circumstances. But I'm still learning about small bore Continentals so take what I say with big dose of skepticism.

For my situation, a DAR is coming up next week to check a friends RV. If a DAR can do field approvals (337s) I may get paperwork in order and save a whole bunch of time.

So ... may a DAR do field approvals?
 
In 2001 my Cub had the Stromberg removed and a Marvel Schebler installed on the C-90-8. With ADs 72-06-05R2 and 98-01-06 done at the same time.

But my 11 is really a J-3C that was converted.
Since the Continental overhaul manual for the C-90 lists the Marvel as an option it should not be a big deal. Mine works just fine.
 
I just found out the DAR that was coming up can't/won't do field approvals.

I'm on the hunt for someone with a 337 to install a MA-3S-PA on a C-90-8F installed on a PA-11. This seems so damn simple I'm surprised that no one has a 337 for this.

Any referals will be appreciated. I need to join the Cub Club too.

George
 
David Lowe has the STC for the c-85, don't know maybe c-90. 270-736-5392
 
George,
Sorry, that was an old number. Try this one.
David Lowe/ Lowe Aviation 270-736-9051 hangar or 270-929-3776 cell
-Chris
 
I had a good conversation with David and learned a few things from a master mechanic. He seemed to support going for a coordinated field approval. I'll be waiting to see what Steve's PMI says. If that is positive I'll go for it. Worst I could do is be denied and just put a Stromberg on her.

Welcome to the world of old Cubs ... I think!

George
 
The small Cont guys and carb guys around here say the Stromberg is a way better carb for the C90 and developes more power than the Marvel. I would stay with the Stromberg if it was me.
 
A "coordinated field approval" is when the project is referred to the ACO by the FSDO for approval. It was implied in a conversation to contact the ACO and request a "one time STC coordinated field approval".

George
 
Alex Clark said:
What was standard on the PA-18-95s??
Click to expand...

Pretty sure there is a stromberg on the one I fly from time to time.

I have a marvel and a stromberg for my C90. I might have to play with them when I get the cub flying.

Tim
 
I think I'm going for the 337 as things are looking up. I prefer the Marvel for four reasons ... 1) easy starts 2) no hesitation/stutter when the throttle is advanced 3) complete support 4) a real mixture control for my annual x-country to Sentimental Journey (I had the Colt under the trees next to the PA-11 in '05 and '06).

When I get the 337, is there a place on this site to post it for the benefit of others who have a C-90 in their PA-11 and want a Marvel. The Short Wing Piper Club has a page just for 337s.
 
Thanks Steve for your help. If you can get to Sentimental Journey this June, dinner of your choosing is on me. George
 
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