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MG Midget and Sprite Technical - Exhaust pipe. One piece or two?

I need a new pipe from my 3 branch to silencer.

I only need the main section. The neck type doesn't matter as I'm cuting it off.

Moss sell a TWO piece stainless pipe.

I can buy a ONE piece stainless, from AH Spares, but it includes a stainless silencer.

I've only ever had a one piece pipe.

Is there any advantage in a two piece pipe?

I can't think of one, and if anything it's just another leak point isn't it?




anamnesis

Yep, another potential leak point but It's cheaper to post two shorter pieces rather than one longer piece...
Jeremy MkIII

Using two does add the alignment flexibility that by rotating the length with the crank can give some degree of fine adjustment and positioning for the silencer box.

Why the downpipe section? I thought you had a 3-2-1 branch?
Dohh! Just tried reading your words!
GuyW

Ah right, the postage cost. Yep, that'll be it then. Lol.

I guess that's so, with a downpipe connection you can twist the rear end. But since I'm cutting it off, it's no use to me. I've already got 2 cut off downpipes. This'll make a 3rd. Lol.

I think I'll ring AH Spares and see if they'll supply just the pipe alone as I don't need the silencer.

anamnesis

Dont think it's just the postage costs. I'm sure I read once on one suppliers website that they now do two parts as most of the mainstream couriers will only accept upto a certain length package.

Trev
T Mason

And yet Moss supply the mild steel version, Part Number GEX1306, as one piece.

Odd.
anamnesis

Trev, its much the same. Most of the couriers seem to have standard limits on package length and size, for their normal pricing. But most will still take oversized items but charge more for these. So size does matter.

A few months ago I bought an exhaust system online and it came in a cardboard carton, 3 metres long. Unfortunately it was faulty but I only discovered this when fitting it and after I had recycled its huge box! The company I bought from refunded and paid for the return but I had to fabricate a new card box using big card boxes recovered from local recycling skips, plus a few kilometers of parcel tape. Took ages to make a strong enough box, 3,200 x 600 x 450.
GuyW

A question on stainless steel grades.

I don't know what grade SS it is, but I have an 'old' 2 box silencer in stainless. The later 1275 cross behind the petrol tank box system. The silencers are still perfect, corrosion free. But the pipe joining the silencers, and the tail pipe, are pretty rusty with pinholes in the joining pipe. Possibly an old Moss 2 box system. I forget.

Anyway, would the pipes have been stainless, or did they use mild steel to join the ss silencers?


AH Spares boast their exhaust system is 304 grade ss.

"They are also backed by a lifetime guarantee."

https://www.ahspares.co.uk/austin-healey/sprite/exhaust/exhaust-system-stainless-steel-1.aspx

How long lasting IS grade 304 Stainless Steel? REALLY a lifetime?

Who're the SS experts here?

304 vs 316 vs 409 stainless steel ?

anamnesis

<< The silencers are still perfect, corrosion free. But the pipe joining the silencers, and the tail pipe, are pretty rusty with pinholes in the joining pipe. >>

Precisely describes what happened to my system. Could be the same supplier, whoever that was. Like you, I don't remember. But it had lasted well beyond 20 years. I would buy another, the same again.
GuyW

Anam,

This links to a site detailing stainless steel types.

https://metalscut4u.com/blog/post/types-of-stainless-steel.html

Grade 304 Stainless Steel: The most widely used stainless steel grade, Grade 304 offers excellent corrosion resistance and is suitable for various applications, including food processing equipment and architectural structures.

Grade 316 Stainless Steel: Grade 316 is commonly used in marine environments, chemical processing equipment, and medical devices due to its superior corrosion resistance

Grade 409 Stainless Steel: Grade 409 is commonly used in automotive exhaust systems and heat exchangers, offering good weldability and formability.


Simon
S Holt

Thanks Simon. That's some list of SS numbers. I had no idea there were so many grades. Anyway, from that it seems 304 is good.

Interesting Guy. Yep maybe we bought the same product, with poor quality pipes. Mine must be around 20 years old too, but I can't find a receipt to date it.

I agree, it doesn't look as good crossing behind the petrol tank. But I like the sound the 2 box stainless makes. It has that kind of hollow noise like an mgb.

I guess at circa 29 years old, I shouldn't grumble, but it's frustrating that the silencers themselves are still perfectly ok. I've been wondering how I might repair the joining pipe. It's quite solid, but has pinholes in places, so I doubt it would take a weld. Maybe wrap in repair bandage and then exhaust manifold wrap to protect it. Just seems a waste to chuck perfectly good stainless steel silencers.

I've also got a single silencer, and again the only thing wrong is the feed pipe rusted. The box is pretty well perfect still. I'm going to experiment and see if I can weld a new bit back on/in, before I shell out circa 200 quid for a new stainless system from AH Spares.





anamnesis

Here's a possible solution.

"exhaust pipe bends and elbows"

90 Degree Exhaust Bend Stainless Steel All Sizes Tubing Bend Swage

£11.79
Free postage


https://www.ebay.co.uk/itm/271602939938





anamnesis

I thought about re-doing mine with new pipe sections. I assumed someone would make them but never got round to searching ebay or anywhere else. The idea got overtaken by an offer of a new system which is fitted, though somewhat noisier than my old one, now stored as a "that's too good to throw out" item. (someone here, he will remember 😀)
GuyW

" -- stored as a "that's too good to throw out".

Yep, that's exactly why I still have mine.

Rylan, remember him? gave me a new single silencer he bought but didn't need. When my twin ss pinholed, I bunged the single on and here I am. 🤣🤣.

Now it's fix it or bin it.

Actually, I now have TWO too good to throw out silencers.

So it's fix *them* or bin 'em.

I want 'emptier' shelves. 😅


anamnesis


As an aside. Another version of BUYING TIPS.

Anybody here used flux core wire to mig before?

I am buying MIG tips for flux core wire. 0.8mm wire. But I've read that the tip should be 0.9mm. As if 0.8mm, flux core wire tends tp get stuck in the tip.

Is that so? Or 0.8mm matched to wire size good enough?

anamnesis

Unless they are hard to come by, I wouldn't think there is any problem with going for the 0.9 tips for 0.8 wire. If that is what the flux core stuff is. Less likely to snag.

I occasionally have used 6mm wire but don't change away from the 8mm tips and the slack fit doesnt cause any problems, there's still plenty of contact area.

I've never used flux core as I use C02/Argon mix in 200l bottles. Just changed one yesterday at £54 which I think is a pretty good price (rental bottle, but free rent!)
My SIP welder has reversible polarity connections but I dont know what that is for. I don't have instructions for it - it was a freecycle acquisition, new, unused!
GuyW

Thanks Guy.

I already have some .8mm flux core, and have run out of gas. Thought I'd have a go gasless, as an 'ugly' presentation on the silencers won't show/matter.

Reverse polarity is I believe for gasless. I *think*, even without flux core, reversing polarity gives a cleaner weld. But don't quote me on that. Lol

Just found this on polarity.

"Don't confuse Flux Cored wire with Gasless wire. Gasless, wire requires you to change polarity. Conventional Flux Cored wire does not"

And

"When the talk of reversing polarity, its like you say, changing the Wire (Torch) from DC + to DC -. And this is only changing the heat distribution, 2/3rds of the heat at the Positive pole and 1/3rd heat at the negative pole. So when welding solid wire and you are on DC+, you get 2/3 heat on the wire and 1/3rd at the welding return (earth)/work piece. I don't have a lot of experience with Gasless wire on DIY machines, but I think its fair to say that All Gasless wires are Flux Cored, but not all Flux Cored wires are gasless........does that make sense?

With your Gasless wires, its easier to imagine them like a MMA Electrode inside out. The Flux coating is contained within the hollow outer shell, which is made from the filler metal. When welded the Flux forms a molten slag which sits on top of the weld and hardens and keeps the pool from the atmosphere so there is no reason for a shielding gas.

Flux cored wires as I know them are use'd in Industry, and are mainly used on DC + (like solid wire) and still have to be used with a shielding gas. They have this flux inside, to add mechanical properties to the welded joint and increase welding speeds, they are not there so they can be used without gas."

https://www.mig-welding.co.uk/forum/threads/flux-core-reverse-polarity.4843/

anamnesis

Hmm? Dont follow that. If reverse polarity gives a cleaner weld, then why isn't it reversed as standard all the time? There must be more to it than that!
GuyW

Dunno. Research needed. Lol

Did you read my following comments? I edited just before you posted. Does it make sense now?
anamnesis

Ah, I read yours before the long edit you added and didn't then refer back to it before posting mine!

Like this classic:
https://www.facebook.com/share/v/14DMZ9ZoXiF/
GuyW

😅. Yes indeed.

I'd forgotten how funny the 2 Ronnies were. Lol.
anamnesis

Turns out, after I ordered 5 .8 mig tips, I already had one sitting in the box of flux core wire.

Anyway, I've been doing some flux core migging. Apart from a bit of splatter, I found it quite good.

Started with the single box with the rusted input pipe. Used a carbid burr to remove the remains of the rusted pipe. Using bits of old exhaust pipe I kept (just in case I might need it lol) I made up an input pipe, and hammered it in.




anamnesis

Bit of flux core welding.

Bit of vht silver exhaust paint.

Turned out nice 😏.

And importantly, it doesn't leak. 🙂.




anamnesis

Flushed with success lol, I sorted the twin box silencer too.

Discovered I still had the 'neck' from the last pipe I bought; -- just in case I ever needed it. Turns out to be pretty well perfect for the job.

Sliced it up to make it fit over the remaining stubs between the boxes.




anamnesis

Final cuts, lined up and tidied up. More flux core welding, and beautification with silver vht paint.

Tested on the car, again no leaks.

Turned out nice again. Lol.

But I prefer the single box. Hence the spare twin goes bqck on the shelf, but now useable; if I ever fancy a change or need a new silencer.

And since I didn't actually need a new pipe after all, because it was the single box rusted input pipe leaking, I've saved circa 200 quid by reparing these two silencers.

And now I done a fair bit of gasless/flux core, I'll buy another reel of flux core, and return my empty gas bottle.

https://youtu.be/P0qyrnGLnsw?feature=shared





anamnesis

Nice, but I couldn't go back to no gas MIG I spent hours trying to get a nice weld, then bought some gas and thin wire and it's IMO so so much easier
Malc Gilliver

I agree broadly, esp' on visible panels.

But I've run out of gas, and rarely do any welding now, so didn't want to buy another fill up.

Plus I already had a reel of flux core, and this welding only needs to be sound, not pretty.

Actually, you can get quite a nice weld, and you can weld outside in the wind. I found a good instruction on line about angles and distance with flux core. Pity I didn't find it BEFORE I welded my silencers. 🤣🤣.

https://www.millerwelds.com/resources/article-library/flux-cored-welding-the-basics-for-mild-steel


anamnesis

Nice job Anam. Well done!
GuyW

I ended up making mine with SS pipe, bends and silencer from fabco. Really good quality stuff, better than my welding!



Rob Armstrong

Anam
Your gasless welding looks better than my "with gas" welding 😮

George Formby - that's going back!
Bill B

Wow, those are a complicated set of welds Rob. You'd need to be good to do that. I only did mine because it was simple.

Cheers Guy. If you have a bored 1/2 day to waste, and a spare pipe neck, you can fix your too good to chuck out twin silencer, for almost free too. Lol.


Thanks Bill. I did find flux core quite easy. But I also used the grinder to 'dress' it. 😅😅.

You know, I really like George Formby. Must have heard it a lot when I was a kid. But his tunes and lyrics are great imo.

I'm leaning on a lamppost at the corner of the street
In case a certain little lady comes by, -- '

Whose done that or similar? Lol

https://youtu.be/vEymZ3rXOmc?feature=shared

Mind you, these days, it's called stalking. 🤣🤣🤣. Such cobblers. Soon there'll be no way to engineer a 'chance meeting' for a 'romance'. Lol.





anamnesis

This thread was discussed between 05/06/2025 and 13/06/2025

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