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MG MGA - Carburettor leak

I have a standard SU set up.I have just noticed under the front float chamber and under the fuel pipe connection joint alongside the rear float chamber, there is a browny coloured gunge. Would I be right in assuming this is from leaking fuel? It doesn't look like, or smell like petrol, but the only other fluid in the vicinity, is the oil in the dashpots.

Thanks
Graham V

I can answer my own question. There is definitely a leak from under the front carburettor which I will have to sort out.
What I didnt know was fuel turns into that browny gunge
Graham V

I am about to order the new seals etc for my carbs. I intend to replace both the rubber grommets for the float bowls and also renew the jet seals, while I have it all of the car, even though I did it all only three years ago.
I see Barney and others recommend Teflon o-rings instead of the cork washers in the jet assembly (two o-rings for each cork seal).

But I cannot seem to find a supplier. Does anyone know where I can get the “last a lifetime” teflon o-rings?

Thanks
Graham V

Graham
I've used the green rings from air conditioning sets a couple of times and they seem to be good
They make heaps of sizes ,diameter and section , I even found some for the bowl/hose fitting, a trick is a squirt of silicone lube or even a smear of oil on the o ring so it slips into place nicely , this will prevent the edge of the o ring getting nicked/damaged during assembly
Don't forget to make sure you get 'all' the old o ring out of the bottom of the fuel bowl, the last thing you need is a piece of that getting into your jet tube /hose assembly--

They are the rings used with 134a gas, it's the common automotive ac gas used here now and I 'think' over your way as well---should be anyway

For use with R-134a. The green O-Rings are Highly Saturated Nitrile (also known as Hydrogenated Nitrile) and are commonly referred to as HNBR or, in some cases, HSN

They're a tiddle softer than black or blue O rings but hold their shape well

If you went to your local Automotive airconditioning service centre they should have an assortment of sizes for you to choose from

Have fun-stay safe
willy

William Revit

McMaster Carr in the US have them. You can order from UK. I have bought from them. I use (3) in place of each cork seal.
Internet search in uk should turn up a local supplier. Size details on MGAguru website.
Mike
Mike Ellsmore

Thanks Willy and Mike. Very useful.

It seems to me that as well as those two small cork seals, the third larger cork seal must also be a potential weak point with modern fuel. I have see the Burlen site has a “super dry jet bearing kit” (WZX 1775) but it’s not available, but what is available are those three seals in “super dry” form (WZX1779) http://sucarb.co.uk/replacement-superdry-seal-kit.html. It says they won’t fit into the standard cork set up, but I am not sure why. It looks the same to me except (depending on the accuracy of the description) the cupped washers are replaced by steel washers.
Have you come across them anyone? Surely worth a go for the price?

As I don’t want to have to do this job every couple of year ( did it in only 2017), I was thinking to help seal the grommets beneath the float bowls, I would add just a tiny smear of holymar blue. I did that on my fuel sender unit and it sealed nicely. Not too much I know. Any views?

Thanks
Graham V

Haven't experienced the superdry kit Graham so can't comment really- sorry, but as you say probably worth a go for the price
Personally I don't like glues and sealants on fuel fittings but if you've had luck with hylomar blue--
William Revit

The only problem I have with the large bottom cork seal is when someone may not tighten the big nut all the way to solid landing, leaving the jet bearings loose. The it will have all sorts of problems, including leaks and wear of the jet and needle when not properly centered. And of course not being able to adjust fuel mixture when the lower jet bearing is free to rotate. When the large bottom nut is properly tight, the cork washer never leaks. For me, it always works well, so no need to fiddle with that one.

"Superdry" Seal Kit may be a can of worms in my view. I have very good luck using Teflon O-rings without leaks, so anything more complex looks like a solution looking for a problem.

The Superdry kit is not just different replacement seals, but also includes different mechanical parts (not compatible with original style seals). It may work well, but the non-compatible bit may come back to bite you later with addition cost and more inconvenience. This is a single source kit, so if/when you may need replacement seals they have to come from the same source. Having to place a separate order for a few seal parts is an inconvenience in itself. If/when that single source or specialty part may dry up or be unavailable, you're just SOL, having to remove the special parts and reinstall original type parts (which you then have to buy again if you tossed out or misplaced the originals).

In fact there is a note on the supplier's web site stating specifically, "Due to the wide variety of kits we produce, some are not held in stock and may need to be built to order". How much of a delay are you willing to tolerate when your carburetor may be leaking? If I was to use the Superdry seal kit, I would be compelled to purchase and keep spare seals in my possession at all times. And that still does not guarantee they will be available far into the future.

I have had a few other parts like this that seemed like a good idea at the time, but are no longer available. For instance, intermittent windscreen wiper control, electronic voltage regulator (for generator cars), certain cruise control models, electronic radios, power antenna, electric window winders. They are fun while they last, but not fun when you need a replacement part that no longer exists.

When it comes to something that is required to make the engine run, and may not be easily available in the future, I don't want it in my car. -- $0.02
barneymg

Graham

I have fitted the Superdry seals and parts to my car. I did one carb several years ago and then the second one last year. The metal parts included in the kit are very similar to the ones using the cork gaskets and nicely made. I have been very pleased with them and it was very easy to fit. The seals have a double lip for the jet and the housing so should give a better seal than a round O ring seal.

I had no trouble getting the kits in the past. I think I would trust Burlen to have the parts available for a long time, although surprised they don't have stock now. You could always buy a spare set of seals for £4.50 each if you were worried.

Best John
John Francis

Thanks Willy, Barney and John.
I will take Barney's advice. But as the "super dry seals" appear only to be compatible with their own jets, etc which are unavailable, I have little choice, anyway.
For the purposes of the archives, I have purchased via ebay, a set of Viton O-rings that include 8 jet seals (2 to be used in tandem at each point) and also the 2 large bottom seals, again in viton.
And I have 4 rubber grommets for the float bowls in my store, so I am ready to go as soon as the ebay order arrives.
I hope they work better than the cork, as I find that bottom bolt under the rear carburettor an absolute pain to remove and replace.

Thanks for your input

Graham V

Graham, try removing carburetors and inlet manifold as an assembly, so much easier.
Mike
Mike Ellsmore

Mike
Thanks for the suggestion - appreciate the help although on my car the heat shield looks like it may well block full access to those bolts.
But anyway, as I dont really want to wait around for a new gasket to arrive for the inlet manifold, I think I will press on this time around.
I will let you know how I get on
Graham V

I said I would report back on how I got on. I do hate it when the OP doesn’t do that.
The Viton seals arrived promptly and frankly I thought very reasonably priced at £7.50 including postage.
They fitted easily, as suggested, I used a bit of oil to help everything come together more easily.
I used to complain how difficult the job was. Removing and replacing the air filters, and working with that lower rear carb bolt. But now it’s all seems so easy. I had always taken both carbs off together. But I now realise I just need to loosen the throttle linkage, and undo the connection between the two choke levers. Then the front carb comes off on its own, and that leaves much improved access to remove the rear carb.
I am guessing that’s the way you are supposed to do it and I have just learned the hard way!
I replaced the air filter bolts with long “furniture bolts” that run right through and come off and on very easily. The advantage of furniture bolts is they take a small Allen key at the head. Happy to share some photos if anyone is interested.

Anyway thanks for your support as always. Took the car for a spin today, after tuning it, and was very pleased with the results.
Graham V

This thread was discussed between 15/05/2020 and 26/05/2020

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