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MG MGA - 'O' rings instead of cork?

Now that the engine is out of the car (thanks for everyone's advise), I am starting on the carbs....
Basically they are in good shape , but need some new seals, etc....
I purchased the SU kits from Moss, and also , upon advise from a fellow enthusiast, purchased the "O" rings for the jet seals....
Here's the problem...With the "O" rings in place, and the lock nut tightened, I can barely move the jet up and down...It is really tight!....I lubed the jet, and the "O" rings, but that made no difference.
Have I done something wrong, or is there a way to get the jet to free up enough to work properly....Or, should I just go back to cork (which are soaking in oil)....?
Edward Wesson 60MGA

Edward - common Bauna N or nitrile 'O' rings will not work for sealing the jets (if you think that are tight now, right after installation, wait until fuel is in the system and they start to swell). What you want is teflon 'O' rings. As long as there are no scratches on the outside of the jets, the Teflon 'O' rings will last a lifetime. They are available from Tom Bryant at 207-443-6338. Cheers - Dave
David DuBois

Teflon O-rings, McMaster-Carr part 9559K15, $8.42 per 25. 8 required per car.
Del Rawlins

Thanks...Now the question, why Moss is selling the "O" rings that don't work?....The tech guy said they've never had a problem....
I don't really know if these are Nitrile, but they are black...
I installed the oiled cork ones today, and the jets work perfectly....
If they leak, I will purchase the teflon ones...

My carbs only use two seals per carb jet, one on top of the spring , and one on the bottom...Cupped washer holds them in place.
Edward Wesson 60MGA

ED, I tried the teflon washers and my carbs leaked. I put in cheap o-rings and the leaking stopped.The choke does not stick, but it does run richer. For what it's worth. JOHN
John Gordon

Edward, you put two of the teflon washers in place of each of the original cork packings. So you end up using 4 per carb. I wonder if one O-ring backed up by a teflon ring might also be a good solution? In the aircraft hydraulic systems I work on, a lot of the packings are like that, using square profile seals.

If you want to use regular O-rings, you should be able to source something in Viton that will work from McMaster-Carr.
Del Rawlins

Standard 'O' rings will eventually swell and cause problems, whether they are nitrile or vition will eventually start sticking. If the doubled teflon 'O' rings leak, they were probably nicked when installed. Teflon is very fragile to cuts and nicks, I have always advised people to make sure the outside of the jet is perfectly smooth, with not nicks in them. It is also advisable to use some 400 grit sand paper to slightly radius the end of the jets and stake the sharp edges off the through hole part way up the jet. Careful installation results in many year of trouble free service (I have had them in our TD for over twenty years with no problems whatsoever. Cheers - Dave
David DuBois

I use the teflon O rings in my carbs. They are white in colour. Four O rings go on each carb, two on top and two on bottom of the spring. The brass cupped washers hold them in place. I had polished the jets thoroughly before assembly, and smeared them with a little silicone grease. I've had them in for about six months now and never any leaks. I was told that they last for many years.
F Camilleri

Well, at this point, I will see if the cork starts to leak when I get the lump back in the car....If so, I will try the Teflon...
The "O" rings that Moss supplied couldn't be used at all...I did polish the jets before I re-installed them (very lightly, of course)...
For the momement, anyway, I am considering the carbs done...Now moving on to the clutch....
Edward Wesson 60MGA

Interesting that Moss has not sourced better O-rings yet. The leaky nitrile and viton ones have been a known problem for years. I called them on this almost 8 years ago. The cork ones work fine if you can find them. I haven't tried Teflon yet.
Ira Spector (PA)

This thread was discussed between 15/11/2013 and 01/12/2013

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