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MG Midget and Sprite Technical - 1275 Exhaust downpipe doughnut gasket.

Which way up?

The knackered one I scraped out, looked like it had been in there since the factory. Metal side down. And it seems to fit better that way.

Can someone confrim that?

Metal side down or up?

Lawrence Slater

Metal side up.... otherwise the heat will melt the rubber

Prop
Prop and the Blackhole Midget

Rubber? No rubber in there Prop.
Lawrence Slater

So. Does anybody have the true gen on this exhaust seal?

Metal up or down?
Lawrence Slater

I put the metal side down.

Funny I had that same question a few years back and was really perplexed about it. Nothing gets me more angry then when those donut gaskets leak. Call me nuts I just cant stand it.

The MGA and B use the same gasket, I was surprized to find out. ( Im pretty sure I checked it out at the time and noticed the same part number in the moss catalogs) You might want to check me as its been awhile.

I usualy get crusty manifolds clean by wire wheeling them. I like to clean the beveled edge up where the donut gasket mates to the bevel. I notice that many old manifolds tend to pit and distort the beveled edge.

The new gasket will fill the imperfections pretty well if you put the soft side toward the manifold.

The Metal side seems to help brace against the exhaust pipe well. If you put the metal side up it wont seal up to the manifold as well making it leak and the exhaust pipe will wear threw fairly quickly.

I hate the sound of a leaky sounding exhaust especially on a british sports car that has a great sound like an MG.

Ive had success doing many of them it will work for you too! :-)

I ve always found it strange that no one that asks this question....so from experience this is what I had to figuire out.

It not quite as good as oil suck experimentation but just as tricky...Ha ha ha

Good luck Lawrence!
Steven Devine

Sometimes I would add some muffler repair paste if the manifold was really pitted but on the whole if you get everything lined up properly you should be able to get a good seal with just the donut gasket alone.

Just wanted to add that so you have all my tricks!

:-)
Steven Devine

Oh yea! Many times when cleaning out the old donut off the mating exhaust I would find I needed to grab a piar of vice grips to peel out the old remnants of the old donut gasget. Ive always assumed it was whats left of the old metal strip that was once the metal side of the discarded donut. It makes me think thats how they were placed new.

Let me know what you think. Thats my 2+2+2 cents
Steven Devine

sounds good to me
William Revit

Thanks both.

That's great Steve. That confirms my finding the remains of the metal in the downpipe too. So definitely metal down. And yep you're right about the annoying noise of a blowing downpipe. This one was blowing, and now I've scraped out the old doughnut -- maybe even the remains of 2 of them, -- I'm not surprised.

Cheers.

Lawrence Slater

Well that was fun.

Stated bolting up the flange, didn't think I'd gone that tight, CRACK. One of the bolt hole lugs snapped of the f*cking manifold.

Can you MIG cast iron? I was only looking at that the other day for some reason. So with nothing to lose I aimed the mig at it.

Bloody hell, it only worked.

Not sure how strong it is, but it feels good and tight.

Worst case it cracks and blows, and I ask someone on here if they have an unwanted '73 cast iron manifold for sale. Or I look on ebay. Or I bung a 3 branch on it, since it appears that the cast iron manifolds can't be bought new.

Lawrence Slater

You youst to be able to get rods and arc weld cast iron, a friend of mine altered a pair of v6 manifolds years ago and there still in one piece.
Dave Pratt

I hate those down pipe gaskets. The land rover has one that had to be so bloody tight it stripped it's studs, the p6 has 2 and I snapped 3 and stripped 2 of the 6 studs taking the damn things off. And they still leak!!
Rob Armstrong

Well so far the mig has done the job. The manifold weld has held, and it's not blowing.

I just used regular wire, argon mix gas, and pre-heated it a little with a blow torch. It spluttered a little and doesn't look overly pretty. But I won't lose sleep about that.
Lawrence Slater

This thread was discussed between 25/03/2015 and 27/03/2015

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