Thorp Air Command - T18.net

I have a fuel fitting going into my carb, but once I screw it into place, it is facing about 180 degrees in the wrong direction.

How do you get a fitting to be facing the direction you want it to face and be screwed in tight enough to not leak?

Pretty sure when I put mine in it was a "tight fit ." Had to put a wrench on the carb nut while turing the AN fitting (should do that anyway) . Also the use of fuel lube helped . If it apprears that it is going to be too tight try another fitting . I have found in some cases no two fittings are the same . Different manufactuer , slightly longer length , slighty different cut on the threads , etc. Be careful what type of thread sealant you use . Precision has a bulletin out about the unauthorized use of certain sealants that may break off and clog fuel passages , etc. BOOM !

RB

Hi Ryan,
On the carburetor, I would replace that fitting with a steel one first of all. In my past experience, steel fittings are recommended in that location. I would personally use a good fuel-proof anaerobic thread sealing compound on the pipe threads for lubrication & to help prevent galling, as well as sealing. It is critically important to apply the sealant correctly & avoid the first couple of threads. There are differing opinions about using thread-sealing compounds - as Rich said, fuel-lube is fine. As you approach the proper position you have to make a decision about whether it is tight enough, or whether it will go another full turn. Usually a new fitting will have slight differences in the thread and it will end up tight in a different position than the first one did - especially steel vs. aluminum - as there are sometimes differences in the starting position of the threads. You might also consider going to a straight fitting on the carburetor, and using a 90 deg. female flared hose fitting, if that's what you require.

It seems to me that sometimes those inlet filter adapters have a different type of thread... a straight machine thread instead of a tapered pipe thread, where you would use a different fitting with an o-ring seal & a check nut. I might be wrong. Make sure you've got a female pipe-thread there if you're using a fitting with a tapered pipe thread.

I hope this is helpful.

_________________
John Evens
Arvada, Colorado
T-18 N71JE (sold)
Kitfox 7 SS N27JE

Good point John . I think Lycoming does recommend steel fittings on the engine . It's been a while , but pretty sure my fitting is steel on the carb . I'll have to look .

RB

If you use a straight an6 -to -pipe thread fitting, and a sweep elbow on the hose end, you can set the fitting to the carb 'just right' for tightness. A sweep elbow has much less restriction to flow, which might be important if you are using a gravity system.
http://www.summitracing.com/parts/aer-fbm1389/overview/
The link should show a steel aeroquip 90 degree hose end to AN6 with a low restriction tube elbow.

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Scott Emery
EAA Chapter 326
T-18 N18TE

A close nipple ("Pipe" Nipple, Rich) and coupling always solves those annoying problems. As a side note, be cautious with fittings - a friend of mine had an automotive fitting mated to an aviation fitting on his leaky brake line - one is 45 degree flare, and the other 37 degree (aircraft) flare - make sure they match.

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Fraser MacPhee
N926WM
Serial #279-1
Angel Fire, NM (KAXX)

Whoa! if talking about the fitting for a Marvel carburator it is a straight thread with a nut, O ring and an washer and not a pipe thread. This fitting is the same as the fuel pump fitting and can be positioned at any angle.

I took off one of the fuel pump fittings to see if it would fit into my carburator fuel inlet, and no joy. It was slightly too big. I did some research over on the vans website some folks there had this same issue. Here is a picture of someones carb inlet (which looks just like mine)



Apparently, Van's drawing OP-28 says that a AN823-6D fitting gets installed into the carb.

It has been a while since any carb work , so I went out to the hangar and dug up a fuel pump fitting and tried to fit it to a "spare" MA-4-5 carb . It was too large , so I am pretty sure I used a AN822-6 steel fitting with fuel lube . I'll know 100% when I go to the airport Saturday morning . I'll report back .

RB

thanks for the help Rich. This stuff keeps me confused. I'll be glad when I get this thing installed and flying!

I still haven't figured out AN/pipe size fittings . >:D They don't make any cents to me . Like John and I said you can take 2 different fittings and they will not fit the same in the hole with regard to rotation . Thread cut , length of the fitting (however slight) and manufacturer . I do remember reading somewhere that Lycoming recommends steel fittings on the engine and I think that includes the carb . BOOM !

RB

yes, I will certainly use steel. I'll use a straight adapter coming out of the carb and an 90 degree adapter on the hose like Fraser and Scott recommend. That will solve the orientation problem. Thanks for all the help.

Went to the Aerodrome to do a Maint. check flight and look at that "crazy" fitting on the carb. I did use a steel AN822 fitting and it points to approx. a 45 degree up position (about 2 O'clock) . As a side note while I was holding short at 27R at KSEE the Memphis Belle taxied up behind me ! BOOM ! BOOM !

RB

you da man Rich. much appreciated for checking that.

Don't be fooled RB ..the real Memphis Belle is still undergoing restoration ... The ones an imposter!

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Lee Walton
Houston, TX
N51863,N118LW
KEFD