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MG Midget and Sprite Technical - Header or No Header?

Hello,

I have a MKII midget with a stock 1098 engine. It has the factory exhaust manifold which does not look very efficient to me.

I found a good deal on a ceramic coated header and wonder if replacing the manifold will cause any issues, like having to replace the carburetor needles or making any special adjustments.

The car runs extremely well and I don't want to do something that will change that.

Thanks,
Paul
Paul Noeth

Hi Paul
You should be ok but there are a couple of points--
No1 is when fitting up the header, check the mounting flange thickness to make sure it's the same as the inlet manifold so that the large flat washers press evenly on both manifolds----If it's out you can weld packers to one half of the washers to even the fit up.
Other point is the mixture- If you're just fitting the header alone you should be ok but if you have sports air cleaners or a sporty free flow exhaust as well, then it'll possibly be a bit lean--but that depends on it's current mixture as well.
Any step in improved flow will usually lean the mixture, but with the exhaust the flow is usually controlled by the eficiency/size of the muffler more than anything.
Cheers
willy
William Revit

At the bottom of the header where the pipes go 2 into 1 (LCB) and there is a 90 degree bend, there can sometimes be insufficient clearance and you have to trim back the flat panel.
Daniel

Paul,

Is the new exhaust header for a small bore Sprite (948cc or 1098cc) or a 1275cc car as the small bore engines have a shorter block so using a manifold meant for a 1275cc engine will result in the exhaust hanging down lower below the car.

What diameter exhaust system are you planning to change to? You may not want to go too big if your car is a 1098cc with a stock or mildly modified engine, so perhaps use a 1 5/8 inch exhaust rather than 1 3/4” or even a 1 7/8” diameter system. Too big might be less efficient.

Maniflow manufacture exhaust manifolds for small bore A Series engines and a matching 1 5/8 bore exhaust system: https://www.maniflow.co.uk/index.php?view=product&from=206&product=1295 (as well as ones for large bore engines: https://www.maniflow.co.uk/index.php?view=category&category=206)

If the car is running extremely well, why change it?

Cheers
Mike
M Wood

Thank you everyone for giving me your insights. Most appreciated.

I am on board with every thing that was said. It is Mikes question that I am having trouble answering... "If the car is running extremely well, why change it?"

When I look at the exhaust manifold it does not look very efficient. I have always wondered if the car would run any different with headers. Will the exhaust note sound any more robust? The only way for me to know is to try it. On the other hand, the car does run well and I don't have to do anything or spend any money to keep it running that way. That should be an easy answer.

Thanks!




Paul Noeth

Paul

If you want to change anything, make sure all the tyres are recent, brake discs, front and rear friction material, solid and flexible brake pipes are in good condition, recent brake and clutch fluid and properly bled.

If you want to switch the headers and exhaust you might as well go for a new inlet manifold (Maniflow too) and K&N airfilters for twin HS2 carbs, the mixture might need sorting, then rolling road session and perhaps carb needle changes.

Cheers
Mike
M Wood

Paul, you echo my thoughts.

The O/E exhaust manifold is a big old lump of heavy cast iron. It does the job but as you say, not very efficiently.

My LCB came from Kim Dear at Magic Midget along with a larger bore exhaust and and a single RC 40 silencer/muffler.

It is more efficient and the sound has more bass and is richer - more like an MGB than the stock system. It is louder but not unbearably so and not annoyingly so on longer journeys. It puts a smile on my face especially on starting, it has a nice rasp to it.

The original saucepan air filters have been retained along with the standard carb needles and it runs well although that is down to Peter Burgess setting it up properly on his rolling road.

Jeremy MkIII

This thread was discussed between 27/06/2024 and 30/06/2024

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