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Silverhawk fittings

Quick question: I need to change the 90 degree fitting coming out of the Silverhawk fuel servo to a straight fitting. Are these standard fittings?

They are, but not what you might expect, at least that was the case on mine. There was a 90? installed on the back, for the outlet. When I removed it, it turned out to be a stainless steel AN833 bulkhead elbow with locknut, but with an o-ring under the locknut to seal it. I was expecting the end screwed into the servo to be what in the hydraulics world we would call an SAE o-ring boss fitting.

There is no AN spec that I could find for an o-ring boss fitting (the threads are the same size as AN/JIC for a given tube size); I wound up getting a US-made Parker stainless steel o-ring boss x -6JIC fitting for mine, from a local hydraulics supplier. JIC and AN are nominally the same, but the thread spec on JIC is looser and in principle means less fatigue life and lower pressure capability. More of a concern with aluminum than steel. I qualitatively compared the AN fitting I removed with the JIC fitting I installed under 10x magnification. I couldn't see a difference. I was looking for cut vs. rolled threads, since JIC allows the former but AN doesn't. It appeared to me that the Parker JIC fitting I inspected had rolled threads. Hardly definitive, but I feel comfortable using the fitting, especially since the fuel pressure is only a few psi at the servo outlet.

For what it's worth, I use those fittings routinely on a large high-g (in excess of 75g) hydraulic shaker with oil pressures around 4000 psi. Never had a fitting fail, though aluminum is verboten on our machine.

If you are interested, the Parker part number is 4 F5OX-SS. Be advised that the supplied o-ring is nitrile; as such it may have trouble with alcohol-laced fuel. If that's a concern, I have the correct size viton o-rings that solve the problem. I have way more than I could ever use, so I can send you one if you'd like.
 
Bob---they are -6 flare (AN) to o'ring fittings.
How's it coming?
Tom

Slow, but forward. If I can get some of the Minnesota types to stop by sometimes and help me plot an appropriate fuel line route, I'll be needing another fuel line.

I also have to can my stock oil lines and get them shorter (buying Van's stock hoses was a huge waste of money).

Can you refer me to a supplier for the Silverhawk-appropriate fitting? I don't kow the difference between a regular fitting and a fitting-to-o-ring.
 
Here's a crappy iPhone pic of the exact fitting. Just looked, lo & behold I have another one.

i-cpVM9wP-L.jpg


I'll never need it, and if I do, I can get lots more. Want it?
 
Use the correct fitting

What you?re looking for is a fitting for the metered fuel outlet fitting (I believe).
DO NOT use the hydraulic fitting shown in the picture above. While it may work, the hex does not correctly trap the O-ring in the boss. If you cannot find an AN815-4 fitting give me a call and I will send you one. It?s surprising that Precision does not tell you guys what is the proper fittings to use in their servos, especially for the fuel pressure fitting on the servo. We have gotten some of these servos back from customers for repair and the fuel pressure fitting has been run into the inlet screen destroying it. But hey it?s only a $200.00 part to replace!!!!!!!


Don
 
What you?re looking for is a fitting for the metered fuel outlet fitting (I believe).
DO NOT use the hydraulic fitting shown in the picture above. While it may work, the hex does not correctly trap the O-ring in the boss. If you cannot find an AN815-4 fitting give me a call and I will send you one. It?s surprising that Precision does not tell you guys what is the proper fittings to use in their servos, especially for the fuel pressure fitting on the servo. We have gotten some of these servos back from customers for repair and the fuel pressure fitting has been run into the inlet screen destroying it. But hey it?s only a $200.00 part to replace!!!!!!!


Don

So I'm learning something here myself. Reading between the lines, in aviation applications, it appears that there is no such thing as an o-ring boss fitting as used in hydraulics. Instead, bulkhead or union fittings such as an AN815 or AN833 are used, with the addition of an o-ring. Is that correct? Do you know where I could find the spec for the spotface and chamfer that create the o-ring seat? Presumably it's different than MS16142/SAE J514 if the hydraulic fitting I photographed won't capture the o-ring.

I just want to understand this better. I searched everywhere I could think of, including AC43.13, and couldn't find anything on the subject of o-ring boss style fittings as used in aviation, back when I needed a straight fitting myself.

I'll gladly swap out the one I have myself for an AN815 if it's a safety issue; I probably have one. What seemed weird to me when I wanted a straight fitting was the the 90 degree fitting I removed was an AN833 with the long (bulkhead) end screwed into the servo. There was a nut on the fitting to capture the o-ring and allow positioning of the fitting. It just seemed strange that they would do it that way instead of using an o-ring boss fitting designed for that purpose.
 
O-ring boss ports and such

Yes your picture is correct Bob. AN815-4 will work as an O-ring fitting with the addition of an O-ring at the base of the threads. The correct O-ring boss for use with AN fittings is MS33649 (that?s what we use when we manufacture our fuel injection regulator bodies), although in a pinch if all you have is a JIC port tool it will work.

When you install a 90 or 45 degree fitting (AN833 or AN837) you would use a bulkhead fitting with the jam nut (AN924), but there again you can use a hydraulic O-ring boss to JIC fitting. These have a washer abs jam nut made part of the fitting to seat the O-ring in the boss port. That?s what Precision uses for their 90-degree inlet fitting and some metered outlet fittings.


Don
 
I just talked to Don Rivera. I got a little education on the nuances of o-ring fittings in aircraft fuel systems. Go with the fitting he advises. There are subtle differences in the o-ring chamfer from SAE J514 to MS33649.

I'll add one more thing: don't overtighten these fittings, in any case. The o-ring is sealed once the fitting is bottomed. The spec on Precision Airmotive's site says 45-50 in-lb for this fitting.

Everything everyone has said about Don is true. What a nice guy. He spent 10 minutes on the phone with me today answering my questions and sharing arcane details about fitting design. Thanks, Don!
 
I don't mean anything by this, but...

this is why I have chosen to use Airflow Performance Fuel Injection on my bird...
 
You know, I read some of the conversations some of you have in this thread and elsewhere and I think, "I'm really not smart enough to build one of these." ;)

That's not true Bob. You're more than capable. To be honest I get a little frustrated with you when you talk like that. Not just you but others too. You must remember that you just don't have all the experiences everyone else has all wrapped up in one person. That's all.
 
That's right.. No one person has all the answers around these things! That's what makes the RV community great!
 
Bob, you are not alone!

I'm also installing a vertical induction IO-360, SilverHawk system, and have not yet run the fuel lines, so followed this thread with interest. I, too, am left with questions.
This is not at all a criticism of those responding, but rather reflects the vast gulf between what, say, Don at AirFlow knows, and what I know about fuel injection systems and aircraft fittings (nothing!).
Your question about whether the fitting (pictured) would work, with an 0-ring added, for example. The answer was yes, but I wonder - what type of 0-ring? Rather important, but presumably so obvious, no need to mention it.
Or, in a few spots (mechanical fuel pump, for example, or constant speed oil line) there is a fitting with an o-ring and a lock nut. How is that oriented and tightened?! Lars says the "o-ring is sealed once the fitting is bottomed". Is he talking about that kind of fitting? What does "bottomed" mean? I screw the thing in to the correct orientation, and it is not "bottomed" (I can still turn the whole thing) but I can then tighten up the lock nut against the 0-ring. Is that right? How tight?
Very grateful that people who know about these things respond to these posts. Please, when you do, assume that there are readers who really do know almost nothing and craft your responses accordingly!
This question of Bob's is directly connected to the very valuable recent Van's comment on safety and related thread. We all have to get the firewall forward stuff right!
Bill Brooks
Ottawa, Canada
RV-6A finishing kit
 
Installation of fittings

Bill you are correct in your assessment. There are people frequenting this forum with knowledge in specific areas. The beauty of this is you can tap the brainpower of many people, or as many manufactures are listed on Doug?s site, just give them a call. As with our company we are willing to help out (within reason) people?s questions on fuel system installation issues as well as troubleshooting the fuel system in your installation. You never know where this exchange of information may lead, but for us, hopefully to another sale of our equipment and another satisfied customer. Sometimes the answer you want to hear is not the answer we give, but in our case we deal in facts. And of course sometimes there is more than one correct answer.

For whatever reason what seems common and straight forward mystifies some people. For instance the bulkhead fitting you mentioned. We see these fittings installed incorrectly all the time. Take a look at the fitting and you will see a smooth section between the threads on the part of the fitting that is suppose to screw into the port. The smooth section is where the O-ring is supposed to be when the fitting is seated in the port. If you screw the fitting in to far the O-ring will get cut on the threads of the fitting next to the jam nut, conversely if you don?t screw the fitting into the port far enough the O-ring will get cut on the first set of threads on the fitting. It?s pretty simple to see if you take a look at the fitting and the port. Typically there is enough smooth section on the fitting to allow 1 ? turns of the fitting when the fitting is seated in its correct position to not cut the O-ring. In any case the fitting is not "bottomed" as this will surely cut the O-ring. As far as the material of the O-ring is concerned the manufacture should specify what material is to be used based on the conditions and service the part is in. If you don?t know then call the manufacture or get a copy of a Parker O-ring handbook. There is plenty of engineering information in this document to inform you of the correct materials and installation methods.

Hope this helps.

Don
 
This question of Bob's is directly connected to the very valuable recent Van's comment on safety and related thread. We all have to get the firewall forward stuff right!

That's one of the things that has concerned me greatly is how LITTLE information there is about firewall forward material easily catalogued and organized (I miss you, Tony Bingelis). I mean, sure, if you spend months patrolling all the various spots and you happen to catch the correct thead, you can get a shred of it and then add it to all the other little shreds. A checklist of tasks for engine installations, for example, would really be a step in the right direction.

Remember when we first drilled HS410 and HS414 way back when we started these things. Remember how careful we were? That's the same attitude we need to bring to firewall forward.

I don't know one O-ring from the other. I obviously don't know one fuel servo fitting from the other and you can repeat this infamiliarity from one component to the next in the engine compartment. The problem isn't that I don't know how to get that information; the problem is I don't know what I don't know.

This is a pretty important part of the overall project and I appreciate Van's safety letters, but the fact is at this part of the project, Van's kinda says "you're on your own. Good luck." I can certainly see why; there are too many varying installations to be able to do anything but leave it to the builder to figureo out.

The information that Don has provided here, it seems to me, is invaluable, and it concerns me that the way a typical builder would learn it is a total crapshoot of luck and serendipity. Which is a bit of a shame because this is wayyyy more important than primer. (g)
 
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doing it right should be "low hanging fruit" of safety

I don't criticize Van's for not providing a paint by number or step by step for firewall forward. Even if he did it would not address important "gotchas" that relate to workmanship and technique.
I am now working firewall forward and fuel system plumbing (IO-360, vertical induction, AirFlow pump, Lightspeed ignition).
Are the hoses properly supported, how close can they be to an exhaust, what sealant if any should I use for an oil line, for a fuel line, how does that o-ring fitting get tightened? (thanks Don, now I know (except for how tight the lock nut should be), and it does makes sense.
When I make an aluminum fuel line with a Parker Rolo-Flair, what do I look for to make sure that the flare is done properly and won't crack or break after it is installed? Is that short aluminum line that I see some people have installed from a fuselage bulkhead or wing root gascolator to the tank at risk of cracking as a result of wing/fuselage flex? Or is that a silly concern.
This building thing is by definition in part for education - I get that and it is part of the appeal - but the consequences of getting any of this wrong contribute directly to the statistics we are trying to improve upon.
Reducing accidents from construction errors should be low hanging fruit. Unlike changing attitudes about, for example, flying single engine at night where reasonable people may reasonably disagree about what constitutes an acceptable risk, I am sure that nobody thinks flawed workmanship in a flight critical system is acceptable.
I am not an A&P mechanic but I am building a plane and want to do it right.
I will have inspections, but not everything can be easily inspected. I know I would benefit from a resource (a book, series of articles, whatever) that addresses the things every builder comes across. I think the safety stats would too.
Bill Brooks
Ottawa, Canada,
RV-6A finishing
 
o-rings, etc

Since I stepped in this one with my first post, here's some information to augment Don's last reply.

The Parker O-ring Handbook is the Bible of seal engineering information, except unlike the Bible, they used to be hard to get. Mine is 25 years old; I had to beg for it and I don't let it out of my office. Except like so many handbooks, now it's available online.

It's pretty obscure for the non-technical user, and even for the more technically minded, there's a lot there. Still, it decodes the numbering systems that specify o-rings, and that can be helpful.

Here's a photo of the AN833 fitting that came off the outlet port of my fuel servo. You can see the groove Don mentioned, and the o-ring and nut. Note that in this case the o-ring is riding on the threads. That's how the fitting came off my servo. Not good. That would probably have leaked. The o-ring is supposed to be in the groove.

i-V6j4fKP-L.jpg


Expanding on the posts about lack of FWF knowledge... My gripe related to this topic is that, despite 25+ years of experience with hydraulic fittings, o-rings and seal design (but not in aviation) I'd never heard of using what I considered bulkhead or union fittings for o-ring seal applications. And if you buy one of those fittings from Aircraft Spruce or other sites frequented by homebuilders, they don't come with the correct o-ring, nor is there any reference to it. And I still wouldn't have known if I hadn't responded to this thread, leading to Don Rivera's timely reply.

I'm lucky that my combo of engineering experience and lifelong hobbies of auto and motorcycle wrenching have had given me some cross over to aviation, but obviously there are still big (and potentially dangerous) holes in my knowledge. Trying to get this done with no technical background must be really intimidating.
 
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Lars,
thanks for the reference - I don't mind the learning, it is not knowing whether I have it right and am not missing something. I consider myself fairly mechanically adept (restored old British cars, rebuilt engines etc..) but aircraft have their own technologies and systems, and of course failure is more than pulling off to the side.
Bob, I apologize for the massive thread drift!
Bill Brooks
Ottawa, Canada
RV-6A finishing
(Hartzell installed for first time)
 
The information is out there

Well, we do offer a Fuel Injection 101 class twice a year. In this 2-day session we cover all the intricacies of fuel injection systems, and their installation. These types of issues are covered in the class. But hey, I guess everyone knows this stuff because we canceled the spring class. No one signed up. Next class is the first weekend in November 4-6.

Any takers???

Don
 
Well, we do offer a Fuel Injection 101 class twice a year. In this 2-day session we cover all the intricacies of fuel injection systems, and their installation. These types of issues are covered in the class. But hey, I guess everyone knows this stuff because we canceled the spring class. No one signed up. Next class is the first weekend in November 4-6.

Any takers???

Don

Hey Don - how about updating your profile (and/or signature) to show your location? Anytime I see something that might be interesting (to see, do, or buy) on the forums, I check to see if it is something within a reasonable distance. If others are as lazy as I am, they might not take the effort to do a search to find the link to your company or where you are. That might affect how many people sign up for the class. I'd love to see something like this - I find fuel injection training manuals to be hard to follow.

Paul
 
Well, we do offer a Fuel Injection 101 class twice a year. In this 2-day session we cover all the intricacies of fuel injection systems, and their installation. These types of issues are covered in the class. But hey, I guess everyone knows this stuff because we canceled the spring class. No one signed up. Next class is the first weekend in November 4-6.

Any takers???

Don

I would love to attend- from the description on your website it sounds like a great course. Time and especially distance is the problem for me, at least right now while I'm building (siphoning off all excess time and money). Eventually though I hope to make a point of it.
 
But hey, I guess everyone knows this stuff because we canceled the spring class. No one signed up. Next class is the first weekend in November 4-6.

Any takers???

Don

Sarcasm aside, I don't think you're understanding the view of the non-expert builder who's working like crazy to try to pull information from a million different places in order to keep from burning alive in an airplane thousands of feet above the ground.

I'm sorry nobody showed up but I can assure you it has nothing to do with with everyone knowing this stuff. My guess is they didn't know about it. Obviously they do now.

It's an underreported and unacknowledged fact of airplane building that the builder has to work VERY hard to gain all of the knowledge that's required to properly build an airplane. It's not in the best interest of the kitmakers to tell you this up front.

But, as I said earlier, if you don't know what you don't know, it's mighty hard to know what to do about it.

I know people pooh-pooh the idea of some sort of checklist of major things people need to know, especially firewall forward. I get it. It's a "real airplane builders don't use checklists" mentality. But people either want these things to stop crashing, or they don't. And it would be a great first step if the best and brightest RV builders in the business could put their heads together and come up with a page on a Web site -- this one perhaps? -- that says: "These are the steps you need to follow in this process and here's a link that has all the information you need on this particular component."

I mean, just look at this thread -- O-rings and the importance of using the right one. Multiply that by 100 different potential causes of problems and the challenge is obvious.

It would be a great step toward improving the safety of homebuilt airplanes.
 
Finding the information

Bob, there is no place for sarcasm here. This is ?deadly? serious stuff. I understand what you mean, but it is kind of like me diving into the workstation here at my desk cause it doesn?t work or putting ?signature? to show my location. What does that mean? I don?t have a clue about how computers or programming work and don?t really want to know, just that it works when I turn it on. But even though I don?t care to work on electronics (why do you thing we build mechanical fuel injection systems) I am forced to learn how to program a SDS fuel injection and ignition system on a Rotax. With my limited knowledge of automotive computers, this is a large task. Just figuring out how to get into the program is a dilemma; there are 86 pages of stuff to read. For a computer savvy dude or a 14 year old it?s probably cake, for me it?s a pain. I?m not even going to try getting into the EFIS to add some new parameters like MAP (it?s a turbo charged engine and there wasn?t any MAP read out. Stuck a 2 ?? MAP gauge in the panel, problem solved). Man I love the mechanical stuff.

But in any case as I said before there are many people who frequent this forum who have specific knowledge of certain subjects. If you don?t know, ASK. It?s probably a lot easier than trying to sift through the chaff to find the correct answer on the Internet or going to the library. I guess I?m still back in the 60?s. When my Dad and I started building our Starduster Too there was a set of drawings to build the structure and then it was pretty much your own doing. Systems especially. But back then most people that built homebuilt airplanes already had a background in aircraft and many were A & P?s (A&E then). As far as information goes for fuel systems we have compiled a 180+ page manual for our fuel injection system installations. You can purchase one if you like or you get the manual free if you purchase one of your fuel injection systems. I see you have chosen a Precision fuel injection system, so you best source of information pertaining to Precision fuel injection systems and their installation is Precision themselves. Here is their phone number. 360-651-8282.



Don
We are at KSPA
 
If you don't know, ASK

That's always excellent advice. But look at the thread. It started with a fitting question and evolved into the use of a wrong O-ring. Is that a big deal? I don't know but I'm assuming that using the wrong O-ring can get you into trouble.

But it never occurred to me to ask. It never occurred to me that it was so easy to use the wrong O-ring.

The stuff that people know to ask about isn't what I think concerns a lot of people who interested in safely building airplanes. It's the stuff they don't know to ask about.

It gives me great pause to think about all the things that might be wrong on my airplane, that I never asked about because it never occurred to me to ask about. In 10 years of building, however, I've asked a ton of questions and gotten a ton of answers. But as I near completion, and especially working on the FF, I grow more concerned about the things that are out there ready to bite you that I never knew were out there.

That's why I'd like to consider getting people together to produce a checklist. It would make a good sit-around-the-campfire activity at Oshkosh this year.
 
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With a risk of sounding like a broken record, I'd like to put in another plug for Don's Fuel Injection 101 class. I?m not associated with his company in any manner except I?m planning to use his system. I?ve mentioned this before, but I took his class in November 2008 and I highly recommend it. Any time a component manufacturer offers first hand information on how their system works, I believe it's a great opportunity. Even if you are not using AFP?s system, you?ll still learn the fundamentals of fuel injection. It's a weekend class that begins on Friday evening with a tour of his shop. It then continues all day on Saturday and concludes on Sunday afternoon. The classes are intentionally kept small so there is plenty of opportunity for hands on and questions. Don does a great job of instructing and was able to get the information down to the level that even I could understand? BTW, did I mention he and his wife are great cooks?
 
O-rings and such

Bob,

It wasn?t really about that the O-ring was wrong but the fact that Lars suggested a hydraulic fitting which was really incorrect for the type of port it would be screwed into and then found that the original fitting was installed wrong and the O-ring would get cut. Of course depending on the type of liquid the O-ring is exposed to the material is chosen accordingly. For us since we deal with fuel we use Fluorosilicone or Viton O-rings. Again the material is chosen base on the type of service the part is used in. Fluorosilicone works better for some applications, Viton for others.

As far as a checklist goes, we have one in our manual. It gives a run down of things to check before starting the engine for the first time.

Don
 
Bob's idea

)"And it would be a great first step if the best and brightest RV builders in the )business could put their heads together and come up with a page on a Web site )-- this one perhaps? -- that says: "These are the steps you need to follow in )this process and here's a link that has all the information you need on this )particular component."

Like building a plane, the document would be a sum of a lot of smaller component parts, specific to RVs, so a doable task:
For example,
1. aircraft fluid fitting installation:
- installing a fitting (sealant, torque);
-special fittings found on an RV, like the o-ring and locknut fittings we talk about here);
- method/system to verify that fittings are checked tight and good to go
2. hoses:
- what type of hose for what;
- making a hose and how to test;
- how to determine length of hoses, and what is too long/too short;
- firesleeve -on what and how to install;
- support methods and specific requirements (how long an unsupported loop is OK);
- routing considerations;
3. fuel injection:
- checklist of a good install;
4. control cables:
- hardware for connections;
- if the cable breaks/disconnects, what should happen (throttle opens, closes...);
5. fasteners:
- what kind of locking device for what (internal lock washer, split washer, loctite...);
6. ......

It is easy for those of us not at risk of being asked to produce any of this to be enthusiastic proponents - but it would be valuable - both for the content and its accessibility in one place on this site. Information is useless if it is not accessible. For some things, it would be just a matter of creating a link to an existing resource.
Do those working on a strategy for reducing accidents think there is merit in this? There are enough examples of crashes resulting from fires caused by leaking oil or fuel fittings or failed hoses, engine stoppage from bad electrical connections etc. that there would have to be a positive affect on safety.
And taking the Airflow course on fuel injection sounds like a great idea!
Bill Brooks
Ottawa, Canada
RV-6A finishing kit
 
FINALLY....

.....I see you have chosen a Precision fuel injection system, so you best source of information pertaining to Precision fuel injection systems and their installation is Precision themselves. Here is their phone number. 360-651-8282.
Don
We are at KSPA

I've been monitoring this thread waiting to see how long it would take for someone to finally state the obvious. The people at Precision are great folks and have always gone out of their way to answer my questions. You simply have to call and ask. Before bashing them, at least give them the opportunity to provide the information.

Although the discussion has been interesting, it could have easily gone bad with someone taking bad advice and installing something that was not correct.

Thanks Don for finally giving the advice that should have been Post #2. The following posts could have been the discussion on what Precision's response was so we all could learn what the "correct" fitting is to use.
 
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That would free up VAF for more posts about.... ummmm... what? :D

I'm sure another "Safety Missive" thread would have been launched. Probably on offering bad advice/recommendations where your first offense you get flamed and than reported to feds on your second. The picture of the fuel fitting would have gotten the poster banned from the site and turned into the feds.:D
 
Around my neck of the woods, we have a lot of builder groups, EAA chapters etc. And even on a typical Saturday, a lot of folks poke their heads in the hangar. People are always asking questions and getting answers. I wonder if the percentage of incorrect answers they get is higher or lower than the percentage of incorrect answers they get via the 'net?
 
Back to the issue of installing the fittings. I've finally gotten around to ordering -- and receiving -- the 45 degree steel bulkhead fitting as required. And Lars was good enough to send me some O rings. And Tom has built a fuel line. Guess it's time to install things.

The fitting I'm replacing -- a 90 degree fitting -- was tightened with the jamp nut but once that was loosened, the entire fitting was loose. I'm presuming that is the intent here but I want to make sure. This isn't something to screw up.

Is the goal here to insert the fitting to the point that the O-ring will sit up against the unit...as opposed to having a thread exposed? Or is there a torque value that needs to be applied here for the fitting, and then one for the -- for lack of a better word -- jam nut against the O-ring?
 
Bulkhead fitting installation

The fitting is not tightened against anything. Position the fitting in the port so the smooth section of the fitting will be where the O-ring is when the jam nut is tightened. When installed correctly the O-ring will be in the tapered part of the port in the housing and on the smooth part of the fitting. The jam nut is what will tighten the fitting in place. See the picture posted a page back or so by Lars. You should have around one turn to position the fitting where you want that will keep the O-ring on the smooth section of the fitting when the jam nut is tightened.

Don.
 
O-ring source

I checked with Precision Airmotive on the specific part number for their version of an O-ring, which they said could be used in conjunction with an AN815-4 union (straight fitting) on the Silverhawk fuel outlet. That is a Precision part number 951787 whcih they claimed would be available through a Precision distributor.

Anybody found a $hipping friendly source for that o-ring?
 
I checked with Precision Airmotive on the specific part number for their version of an O-ring, which they said could be used in conjunction with an AN815-4 union (straight fitting) on the Silverhawk fuel outlet. That is a Precision part number 951787 whcih they claimed would be available through a Precision distributor.

Anybody found a $hipping friendly source for that o-ring?

Parker's number is 3-906 for the correct o-ring to fit a 3/8" o-ring boss fitting that meets MS33649.

McMaster-Carr's aviation department sells them as part number 1201T294, $14.82 for a bag of 100 in mil-spec Viton fluoroelastomer.
 
Since it's never been used, I just took the O-ring off the fitting that was on there, and put it on the new one. That's OK, right?

Most likely. As long as it wasn't cut or nicked, it'll work. Obviously an inspection item (around the fitting, for leaks) after you get the engine running, but it would be in any case.
 
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