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MG Midget and Sprite Technical - Protecting the Exhaust Pipe

Is it possible? I'm putting the rusty old one back on, and it's lost a good thickness of steel, I would say. Still solid, but it would be nice to arrest the corrosion.
Nick and Cherry Scoop

You can try painting it with heat resistant paint but eventually it will corrode through. I read that most mild steel exhausts rust from the inside out anyway.
Bob Beaumont

Agree with Bob, you can get a temporary cosmetic effect but in practice I doubt it will extend the life at all.

The old advice of try and avoid short trips applies, combustion makes water vapour and if you don't run the engine for long enough to get the whole pipe hot then the water will condense, accumulate somewhere and accelerate rusting.

AdrianR

Thanks both for saving me a job. Now for the horror of putting it on the car. This is when you really need a lift.
Nick and Cherry Scoop

I remember some years ago, when I bought a replacement exhaust system for one of my cars, (may have been an early fiesta), I noticed a small hole at the bottom silencer. When I queried this, the supplier said it was a drain hole, to reduce water build up, and therefore reduce rust. It seemed to work in that water would drip from the hole when the engine was cold.

Having just googled it I came across the following:

"Bosal has introduced a drain hole to its exhaust systems, mainly in the rear silencer to release the condensate.

The drain hole is a formed 2mm hole at the bottom of the inlet endcap of the lowest part of the exhaust system; this prevents the build-up of corrosion and prolongs the life of the exhaust."

http://garagewire.co.uk/news/exhaust-drain-holes-help-prevent-corrosion-reports-bosal/

Maybe worth doing?

Jim
J Smith

I thought you had done the difficult bit Nick. I was impressed in the photo of your engine going in, that you had remembered to put the exhaust in position first. At least that is what it looked like.

I, on the other hand, have a new Maniflow 3-2-1 to fit to my Austin Sprite with the engine already in place. I am not at all sure that this is possible. I bought the new Maniflow several months ago and have been putting off this job by repairing the old rusted through one in situ with Gungum, which has finally dropped out.

I have just come in from undoing the manifold and carb nuts but will leave grovelling underneath until tomorrow. It might rain.
GuyW

Guy, I believe it is possible, but you'll need to have the car quite quite high off the ground to allow the manifold to rotate into position.


AdrianR

Adrian,
when I bought it I rang Kim, I think it was, and asked him. He wasn't sure. He said that on some cars it would just go in, whilst on others apparently it will not. The problem, as I recall from when I fitted the first one is that the final bend a the bottom tilts the manifold plate towards the rear just a fraction too far, however high off the ground the car is. As there are mixed reports on the feasability of this I did wonder if the design had been altered, but he said no.

I think one possibility is to remove the heater. I will no doubt find out tomorrow. ;-)
GuyW

My maniflow one I purchased last year went straight in. It was tight around the heater box
Bob Beaumont

On the Frog, Bob? No wing in the way.
I do dislike putting exhausts on. It's all trial and error, and a cricked neck.
Nick and Cherry Scoop

Guy,
it helps if the gap at the chassis has been relieved a bit, I'll try to take a photo tomorrow.
Nigel Atkins

7 years ago I had to remove the heater. The new maniflow went in without removing the heater.
Flip Brühl

Nigel mine doesn't have the horizontal plate that some have. And when I fitted the previous one I ground a little crescent off one of the flanges, the one on the base of the triangular web I think. I also had to shorten the end of the pipe where it joins to the front of the exhaust pipe. I am hopefull that the new one will fit OK
GuyW

Guy,
by the sound of it you might be OK this time.

A stab in the dark with my camera shows me that there might have been more(?) relieving than I remembered. -

Nigel Atkins

Replacement Maniflow now fitted and being heated to cure the VHT paint.- it won't fit a domestic oven. There was a difference between the old (16years or so?)and the new. The length of the manifold system between the rear face of the rear downpipe and the tail end of the pipe, where it connects to the next bit of the system. The old one was just over 12", whilst the replacement is about 9". This is achieved by having a shorter single pipe after the Y branch, but the triangular part of the Y branch where the 2 pipes come together is also shorter.

I attempted to remove the old manifold but, just as I recalled, there was no way this would come out with the engine in position. Nothing to do with the height off the ground, its the shape of the pipes relative to the damper mount, footwell front panel and the hole in the chassis that the pipe goes through. Anyway, as it was already knackered I cut it up with a mini-grinder disc and took it out in bits. The replacement just slotted in place as easy as anything. I just had to remove the head steady that my car has. The only complication was the 3 1/2" gap under the car where the shorter version didn't meet the front of the current exhaust! Soon sorted with a section of pipe from the "someday usefull" bin and 10 minutes with the MIG.

Referring back to Nick's original question, when I cut up the old pipe there was zero corrossion on the inside of the pipes near to the manifold. It had a thin even layer of black (soot?) but was otherwise virtually as new. The corrosion had occured where the 2 pipes take a 90 degree swoop under the car, where it had rusted through form the inside, to meet with the scars of occasional contact with speed humps and such like.
GuyW

Hi Nick
yes the frog. It has a 1275. The old one was a challenge to remove. It was a special tuning one but the section where the Y is had over time started to fracture. I welded it a couple of times but eventually succumbed. The maniflow one sits closer to the floor than the ST one and provides a bit more ground clearance. I notice too the the centre branch was a larger diameter than the outer two
Bob Beaumont

Clearance with the new Maniflow installed:

GuyW

I gave it a few light coats of VHT paint. Looking again at my old one almost all of the corrosion is from the ouside, not the inside at all so I am hoping this paint might add a few years to its life expectancy.

One is supposed to cure VHT paint at progressively higher temps, 300 -450 -600F I think but as it wouldn't fit in the oven I had to skip that bit and rely on cooking it gently with engine heat once it is fitted.

Looks nice though doesn't it?

GuyW

I had mine ceramic coated as its meant to reduce underbonnet heat. It was did not overheat last year in traffic but it was not really that hot to test it.
Bob Beaumont

Beautiful, Guy. That Y-piece and pipe certainly is short, though. Have you tried to see how close the T on the steady bracket comes to it? Mine is miles away, and I'm going to ask the blacksmith to extend it.
Nick and Cherry Scoop

I have never used the steady bracket off the bell housing - if that is the one you mean Nick. In fact I am not sure that all of the cars had that. Should there be one on a 1971 car?

Since these one piece manifold and exhaust sytsems are much more rigid than the original CI manifold mated to a down pipe with a rather dubious clamp perhaps they are OK without the steady.
GuyW

I agree entirely, Guy. Essential on the original exhaust system: not on a Maniflow.
David Smith's reply to my speedo cable clip question some days ago implied that later cars had a steady bracket, albeit flimsier than a Frog's.

https://tinyurl.com/y95dz3zy

BTW, I forgot you were talking about your Austin.
Nick and Cherry Scoop

I've wondered about that bracket and strap, the '77 factory parts catalogue shows it on the page for single box system on the list for exhaust systems except 1500, yet Moss have it on and off various models and MGOC varies too.

If I remember correctly a few years ago the brackets weren't available new.

My car's had two different LCBs without the bracket over 10 years but I bought it recently (had the strap a few years back) but I'm undecided whether it's best to fit it or not.

Any info on whether the bracket is necessary and on which models would be useful (if only so that I can take it off the ever expanding to-do-list).
Nigel Atkins

The bracket and strap was on all 1098 & 1275s; don't know about Frogs - I've never had one. I reckon they sometimes 'go missing' when exhaust centres fit new systems and find the bracket broken or badly damaged. They also get omitted when fitting LCB manifolds as the bracket won't fit round the larger pipe. I agree with Guy's analysis that LCBs don't need them as they are more rigid and do away with the floppy bellmouth pipe to manifold fitting.

I have several spare sets if anyone needs one.
David Smith

Thanks for that info David.

I had two and a half years on (too) lower front springs with the exhaust hitting and scrapping at the LCB manifold to centre pipe U-bolt and later thin bolt clamp and the LCB seems to have survive well so I'd go along without the need for the bracket with LCB.
Nigel Atkins

This thread was discussed between 20/04/2018 and 25/04/2018

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