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My M10 1.6 is having some running issues at the moment, the biggest problem being that it overheats, not all the way, just a little bit, unless driven hard.

I suspect the HG may have gone, I'm getting foam in the radiator, and I "think" I can see white-ish smoke from the exhaust. The blowers don't blow hot (only the window demister blows hot?!).

So, I was thinking about taking the car off the road for the winter anyway, while I'm there I may as well get something done about the engine. I've chatted with a few guys off here about engine swaps and while I really would love to do the M52 swap, or even the M20 swap, unfortunately I'm limited by budget, and the amount of custom work involved with engine swaps limits me, even if I could source all the bits cheaply, the upgraded brakes and other bits that would need upgrading, would make the whole lot just too expensive.

So, my plan was to take the M10 out, strip it down and give it a decent bit of TLC. New HG, a good clean out, just generally give it some love.

I was however, thinking about doing a few little mods to it, maybe a new cam, and possibly put it on bike carbs?

I'm not after a number or power figures, but I'm assuming a few little mods are worth doing? As in, I'd notice it at least?

Anything worth knowing or thinking about with regards to taking it out and giving it a little bit of an overhaul?

I replaced the factory solex carb by a weber, after E21-Mark's suggestion(and also replaced the air filter by an appropriate K&N one). Left everything else pretty much as from factory, (well, up to now).
Difference is huge! Even now, that I have been used to it, it still surprises me sometimes.

Was recently thinking of going for a camshaft upgrade, but left these thoughts in stand by mode, as I am also thinking of bringing a bit closer to present my up to now future plans of an engine swap

However, afaik cat cams makes something quite interesting for M10

Good stuff, so it's work worth doing then?

Can't answer that question
It depends on your budget, and on the prices of. The items you find
A used carb is not big money
But if you want something more, I guess you are looking into cams, twin carbs(and appropriate inlet manifold), and exhaust, and these start to raise the budget(and the consumption as well), for not more than 120 hp(I guess), which will be given to you only in high revs, and, are all these worth the money? I mean you are then starting to approach an engine swap budget wise

And of course it all depends on where you want to arrive! A mate has made 185hp out of his 1602, no turbos. Based only in big carbs, wild cams and exhaust, and of course on high compression ratio.
Still not much power and torque under 3000 rpm (but a killer of giants after this point, a veryf ast car)

So, if you are not looking for extreme things, as you stated above, and if you find a used weber to replace the factory solex, yes, do it, you will be much happier

Is your car running on the factory solex carb? If you already have a weber, I am not sure if you are going to have any difference indeed

It's completely standard at the moment, so yeah, single Solex.

I'm not even sure if I'd go down the twin Weber route, I might look into bike carbs.

I'm not after a mental lap record setter. Something with a bit of theatre and noise, with a decent enough amount of poke would suit me fine.

Why bike carbs, can I ask?
I'm not saying anything against it, just never known what the benefits are over DCOE Webers? Cost?
If you're going bike carbs, there will be custom work involved. Have a look at Hakhawk's build thread for some info there.

I've done the Weber DCOE conversion myself, and I love the noise, throttle response, simplicity, and tidiness of the engine bay, but if I were to start again, I'd do an m20 swap (and I think I will at some point). Depending on available second-hand parts and pricing, I probably could have bolted an m20 in for a similar cost, and only a bit more effort.

Or, if you're going to rebuild the m10, you might as well put in a 286 (ish) degree camshaft with possibly a 2L crank and higher compression pistons. And run that with a Weber 38/38.

Or look around for a motor that someone else has built. That would save you time, effort, and probably money.

My m10 used to sit at 3/4 on the gauge but never went over that, old temp sensor?

I can get you a manifold made easily for bike carbs and get them setup all lovely for less than a grand.

however, what I would do is sack all that n/a crap off and just turbo it, that way you have 180hp and little weight and it will give you that WAAAPPPPP WHOOOSHSHHH YATATATTATA and you will laugh your head off every time or m52, either way it will never get boring,


One thing I learnt, there is no easy or cheap solution, budget 5k if you want the engine work / bay to match the rest of your car.

It used to only go to 3/4, but now it's started to move past that, and if driven with some vigour will go all the way over.

I thought about turbo-ing it, but I couldn't find any threads or anything on here.

My knowledge of turbos etc is that it's a very expensive game, or is that a bit of a non-truth? I'm not a fool, I wouldn't bolt a snail on and wind the boost all the way up, I'd be very happy with a low boost setup, for a nice balanced amount of power.

rebuilding a M10 or a M20, M50,...is almost the same price, ok M10 is 33.3% cheaper as it only has 4 cylinders. Depends on how do you plan your budget and who will work on your engine.

DIY is pricy here, more or less Do It Right or Do It Again, no middle way.

You can easily survive work + M20B25 swap or M50 M52 swap for 2 grand, but the engine will be as is, used, and in a shape that it is now.

about the overheating problem, try to get another M10 radiator, i'm most certain that is the problem, I had same issues on mine...old copper coolers and 30 years of age, not good.

could also be a thermostat i might have a spare one donated by Reck. in fact hes probably got one (along with half an e21) he takes everywhere with him in his boot but yeah while the fluid is out flush the rad through.

it doesn't matter what you do on an e21 it will cost you, the best thing about an e21 is you end up learning lots in the process.

I've battled M10 overheating problems the whole time I've owned an E21 and finally got so fed up that I decided to sort it once and for all. I've just had a head skimmed by Lockstitch in Rochdale for £80 - they fitted new valves, lapped them in and replaced the steam seals at the same time too (provided by me). If your bottom end is in good ick that might be all that's required. They're currently boreing and rebuilding the bottom end too - pistons have cost me best part of £400 though, and all the rest (gaskets, seals, bearings, oil pump, water pump) etc. plus labour are going to push it towards £900 I reckon. Then I'll want a new rad to go with it, and a new exhaust system!


Running at three quarters is pretty hot, it should pretty much sit in the middle all the time except under heavy load on a hot day! What are your other symptoms? Are you losing water? Try flushing the rad and replacing your thermostat and water pump - cheap and easy first.

I also have some Dollerto Twin 40's and manifolds sitting in a box that I could definitely be tempted to part with - came with the car when I bought it. I switched to a Weber cause it's my daily and petrol is expensive enough as it is!

Eddie. wrote:It's completely standard at the moment, so yeah, single Solex.

I'm not even sure if I'd go down the twin Weber route,....

Are you sure the carb is a single one? (Mine is the 316 1.6, not the 315, so dual solex 32/32 was it.)
If you replace the single solex by one dcoe weber, or dcd or however it's called, by a dual weber carb, even if you don't go for twin carbs, you'll notice a big difference, I guess, for small money

Reck wrote:I've battled M10 overheating problems the whole time I've owned an E21 and finally got so fed up that I decided to sort it once and for all. I've just had a head skimmed by Lockstitch in Rochdale for £80 - they fitted new valves, lapped them in and replaced the steam seals at the same time too (provided by me). If your bottom end is in good ick that might be all that's required. They're currently boreing and rebuilding the bottom end too - pistons have cost me best part of £400 though, and all the rest (gaskets, seals, bearings, oil pump, water pump) etc. plus labour are going to push it towards £900 I reckon. Then I'll want a new rad to go with it, and a new exhaust system!


Running at three quarters is pretty hot, it should pretty much sit in the middle all the time except under heavy load on a hot day! What are your other symptoms? Are you losing water? Try flushing the rad and replacing your thermostat and water pump - cheap and easy first.

I also have some Dollerto Twin 40's and manifolds sitting in a box that I could definitely be tempted to part with - came with the car when I bought it. I switched to a Weber cause it's my daily and petrol is expensive enough as it is!

Yeah, I'll start with the obvious stuff first with regards to the overheating, but ideally, I'd like to take the engine out and give it a spruce up anyway, if nothing else, for something to do over winter!

Yeah, I've done my best to keep the temperature down on the engine when using it, not always possible though. I know the M10 is a tough old lump, so it hopefully will be okay. In all honesty, for all that work, £900 seems very good to me?

I'd be interested in your Dollerto's, depending what figure you had in mind?

Another option if you wanted to upgrade the carb...

http://www.ebay.com.au/itm/BMW-DCOE-KIT ... 492&_uhb=1

Not quite as good as twins, but easier to tune, less bother with linkage, and a bit cheaper. I think the main benefit over twins was that it clears the brake booster in LHD cars.

I have a mate with that setup on his m10, but I couldn't tell you how good it is, because he originally had it installed on a dying engine, and his new engine is still being built.

But as a guide, my 1.8L m10 has all stock internals, but with twin DCOE Webers, 4-2-1 headers with 2" exhaust, bosch red coil, thermo fan (removed engine fan), and was dyno'd at about 125hp at the crank, which is about 20hp better than it would have had from the factory. So realistically, not a whole lot more power for the cost and effort. The plan was to eventually rebuild with higher comp pistons and cam etc., though now I'm leaning more towards a 2.5 m20.