mk1-forum.net

leon

I think the answer to your question is no one on here appears to have done it ,and so not only are you building an interesting engine , but a very unusual combination of parts too ...good for you ,more power to your elbow . please show us the dyno graph when its done .

incidentally , I have set up quite a few turbo mini engines by filing the needle , with great success, both bhp and economy , so if you get stuck for a needle ,that's always an option .

robert

my experience of 1071's is that they always run better on twins - be it 1 1/4s or 1 1/2s - ive never had any success running them on hif's (apart from initial start up)

I think the short strokes suffer from not been able to lift the piston enough to get the needle to meter in the right place, so they always run rich or week and very boggy.

of course it depends so much on many other aspects such as the cam etc, so what didn't work for me may well work great for someone else.


don't worry about the rod change box, the last 970 I had in a car (terrible thing it was as well) blew its self to bits in the outside lane of the M1 - broken 970 crank?, yep, got one of those

ianh1968 wrote:

AustinSuperSeven wrote:...a very desirable period engine and it would look better keeping it in period with a set of twins!
Putting a 44 on it will just make it look like any old A series from the 80s.

Good point.... Could be a "Street Sleeper" though, a decent 970 should out-perform
your average 1275cc Metro engine anyway.

I ran a 998cc years ago,
12G295 Head 1.312" Inlets, 1.0625" Exhaust, 10.5:1
Offset bush welded-up pressed steel rockers
MG Metro Cam
MG1100 Exhaust
Janspeed Inlet
Modified single 1.5" HS SU, No7 Needle, Blue spring
K&N with a proper shaped "stack"
N7YCC Plugs
etc etc...

When I stuck that lump in, the people I worked with didn't "get" the fact that my 998
would be better than the standard 1098 that came out. In fact, it would obliterate
a 1275GT...

It went to 8000rpm regularly and would out-accelerate a Turbo Metro quite easily 0-60mph.

... until I blew it up one day! The 970 should be fairly bomb-proof!

8000rpm with a 295 and MG Metro camshaft and a single Hs4?
Who are you trying to fool?

Vegard wrote: 8000rpm with a 295 and MG Metro camshaft and a single Hs4?
Who are you trying to fool?

Not trying to fool anybody, I had at least 2 different tacho's on
this engine and they went to 8000rpm, so I can only report what
I saw with my "Mk1 eyeball"...

The last of these tachos was used later on a 1380cc engine which
also showed 8000rpm. The stepper motor type Stewart Warner
which replaced that tacho showed the same maximum 8000rpm.

So two tachos showed 8000rpm on the 1380 and the earlier of the
two had also shown 8000rpm on the 998. So the 1380 and the 998
revved the same, whatever that was...

On Aldon's dyno on more than one occasion, at 7000rpm the SW
was showing spot on. On another dyno, more recently it has also
been spot on at 7000rpm. If the SW was showing spot on at 7000
and that one and the previous tacho showed the same max rpm, surely
it could be assumed that the tacho on the 998 was fairly close?

OK, let me re-phrase:

The engine spec is the same as my previous post, and the
tacho's that I used with the engine showed 8000rpm.

The head had the chambers done on a CNC milling machine and the
throats and the ports were done on a spark-eroder. The head used was
the second attempt as the first one ended up with holes in it. On the
second attempt, the electrodes were not dropped as far down through
the valve holes. You'd be surprised how quickly you can do the throats
and ports with a spark-eroder - and you don't end up with lung-fulls of
iron filings, either!

The inlets were 1300 valves, re-machined to a "Rimflow" shape. The
diameter, at 1.3125" was a 1/16th larger than the 1.250" valves which
are normally considered to be the maximum for these heads.

The exhausts were also cut from 1300 valves and needed the top of
the block modifying to clear them.

The head had throats and ports which were visibly far more open than
a 940 type and it had fairly strong springs on it, probably too strong...

The rockers were offset bushed, but not using bought ones. They were
made oversize on the outer diameter and the holes in the rockers themselves
were bored offset too, so there was a "double offset". The geometry of the
rocker assembly was optimised and custom pillars were made to achieve this.

The carb was quite substantially "done" inside and had a proper shaped
stack inside the K&N, not one of those silly straight ones with about a
1/32" rad in the end.

If someone has built one exactly the same as this, perhaps they would be
able to tell me what the engine I built revved to...


What ever it revved to, I don't really care, it was a great engine and I had a
lot of fun using it!

I am sure the 970 will be great fun as well - Sounds like a sensible spec, to me...

robert wrote:I have set up quite a few turbo mini engines by filing the needle ,
with great success, both bhp and economy , so if you get stuck for a needle ,
that's always an option .robert

Robert, Just re-reading through this thread....

You may be interested to know that the needles spreadsheet that
is available on the Mk1 site will recalculate a filed needle back to
round again.

If you then plug the "round" figures back in, it will locate a proper
profile to match it which is handy if you are building more than one
engine of the same spec.

If you can't get enough fuel at the fat end, you could try modifying
the jets to take 125thou needles. The spreadsheet will tell you
the equivalent sizes for the larger needle, and again, it can be
used to find a proper profile to match.

http://mk1-performance-conversions.co.u ... l_carb.htm

thanks ian,interesting info .

This is my 970 prior to fitting. I fired it up on the floor and looked for oil and water leaks; all good.

Nice, looks very nice.

Would you happen to have a picture of the front, I am always interested in the water pump and water pump pulley clearance. Engine steady is a first time for me, interesting exhaust manifold for your spec.

Wim

Pics of my 970 rebuild;
https://plus.google.com/photos/11743283 ... banner=pwa

dutchacme wrote:interesting exhaust manifold for your spec.Wim

... I think it's one of these:

http://www.minispares.com/product/Class ... o%20search

I was wondering what this freeflow manifold would do for mid range torque and high end revs.

The traditional fit for a 970 with a 649 would be an old skool small bore 3 into 1. Being one of the few combinations where a small bore lcb would loose out.

Wim

There are 2 major themes of exhaust (one of which is mucked up by the siamese ports of a 5 port head). That of velocity and that of resonance. The name of the game is how different sized pipes can allow gas with a given density to give effective pressure at the inlet valve just prior to it opening, and low pressure at the exhaust valve etc.

If you cast your mind back to a slinky spring and make the spring go longer/shorter/repeat you get a compression/rarefaction of a wavelength which is proportional to the speed of the cycle of the piston/valve in focus. So, the faster the engine goes, the shorter the wavelength. With resonance tuning, there are pressure waves which traverse the pipe, rather like an organ pipe, this can be tuned to accentuate a low/high pressure as required at the valve required.

The 3 in 1 system has the advantage that when a pressure wave comes back from the end of the exhaust, it is split more effectively than the shorter Y of the LCB. If you try and visualise it, you can easily see the problem. Longer cams tend to be more responsive to this affect and this can be enhanced by megaphones/short exhaust/etc. You have to remember that the resonant frequency of a pipe is proportional to it's length and the oddity is the speed of sound (which is faster in hot, low density gases) so your usual maths doesn't work.

Taking the 3 into 1 system from the point of velocity extraction, the exhaust valve opens and a slug of hot gas shoots off down the pipe, behind the pulse is a lower pressure area which can extract residual gas which might remain and is facilitated by a longer duration exhaust. So, since a high revving engine will have really fast frequency, it follows that long pipes are unnecessary......

Wrong. They are even more important. When you have a long cam, the gas is less sure about which direction it is travelling in at low rpm, so everything needs to be done in order to maximise this. This means longer tubes to give a better extraction (exhaust) or ramming (inlet). If you have a short stroke engine, by the very nature of it, the pressure difference vs time are going to be less significant which means that the engine will take longer to respond and requires similar treatment.

So, if you take an engine and you fit a longer cam in it, in order to retain low end good behaviour, you need to lengthen the pipes accordingly....In order to maximise a short stroke engine, you need to do the same.

Having twins allows the charge a better "shot" and a better uniform velocity than a 2 into 1 inlet. I know that a MG metro manifold is great, but from a ramming point of view, it's all wrong. If you wanted to run such an engine, it would be a better idea to position the manifold away from the engine using 5" pipes (like a weber manifold) so you get some ramming.

I could explain this better with diagrams.

Matey's 970 engine is going to run short of it's potential due to his lack of understanding of the facts.

However, we can all applaud his motivation, like we can applaud Icarus.

Shall I get a BMW KAD twin cam head for it, then lump a turbocharger on it ? Then I maybe will realise the 970's potential!

A BMW head would be a good idea and fits in with the spirit of ultimate tuning, to which shorter strokes lend themselves to. Turbocharging would be interesting as well, the thing would be that the low down torque would probably be affected by the resistance of the turbo itself. Both of these things are in the spirit of minis and in the spirit of mini tuning, which is the essence of the car.

How about putting a Massey Ferguson exhaust pipe on it, or a Maxi cylinder head, perhaps you could even take the innards out of a series 2 morris minor gearbox, just to handicap the thing even more.

Your idea will not make the most out of an engine. What you are doing is taking a real piece of rare and interesting hardware with some serious potential. Not only are you not making the most out of it, you are handicapping it.

These guys may encourage you, I sadly think it's quite a waste of components. Hopefully you will get tired of it and do it justice, or sell it to someone who will.

I almost get the impression you are deliberately trolling.

Of course the main trouble with this, is that isn't a 3 into 1. It's a short LCB.

In the shed wrote:There are 2 major themes of exhaust (one of which is mucked up by the siamese ports of a 5 port head). That of velocity and that of resonance. The name of the game is how different sized pipes can allow gas with a given density to give effective pressure at the inlet valve just prior to it opening, and low pressure at the exhaust valve etc.

If you cast your mind back to a slinky spring and make the spring go longer/shorter/repeat you get a compression/rarefaction of a wavelength which is proportional to the speed of the cycle of the piston/valve in focus. So, the faster the engine goes, the shorter the wavelength. With resonance tuning, there are pressure waves which traverse the pipe, rather like an organ pipe, this can be tuned to accentuate a low/high pressure as required at the valve required.

The 3 in 1 system has the advantage that when a pressure wave comes back from the end of the exhaust, it is split more effectively than the shorter Y of the LCB. If you try and visualise it, you can easily see the problem. Longer cams tend to be more responsive to this affect and this can be enhanced by megaphones/short exhaust/etc. You have to remember that the resonant frequency of a pipe is proportional to it's length and the oddity is the speed of sound (which is faster in hot, low density gases) so your usual maths doesn't work.

Taking the 3 into 1 system from the point of velocity extraction, the exhaust valve opens and a slug of hot gas shoots off down the pipe, behind the pulse is a lower pressure area which can extract residual gas which might remain and is facilitated by a longer duration exhaust. So, since a high revving engine will have really fast frequency, it follows that long pipes are unnecessary......

Wrong. They are even more important. When you have a long cam, the gas is less sure about which direction it is travelling in at low rpm, so everything needs to be done in order to maximise this. This means longer tubes to give a better extraction (exhaust) or ramming (inlet). If you have a short stroke engine, by the very nature of it, the pressure difference vs time are going to be less significant which means that the engine will take longer to respond and requires similar treatment.

So, if you take an engine and you fit a longer cam in it, in order to retain low end good behaviour, you need to lengthen the pipes accordingly....In order to maximise a short stroke engine, you need to do the same.

Having twins allows the charge a better "shot" and a better uniform velocity than a 2 into 1 inlet. I know that a MG metro manifold is great, but from a ramming point of view, it's all wrong. If you wanted to run such an engine, it would be a better idea to position the manifold away from the engine using 5" pipes (like a weber manifold) so you get some ramming.

I could explain this better with diagrams.

Matey's 970 engine is going to run short of it's potential due to his lack of understanding of the facts.

However, we can all applaud his motivation, like we can applaud Icarus.

I'm not about to enter this debate, I have my own views on it though

However not withstanding this, I would like to say a sincere thanks to In the shed for explaining these inter-twined subjects so simply and well, especially since this is a very complex topic.

https://www.google.com.au/search?q=helm ... ent=safari


This is an interesting subject in terms of exhaust and inlet, air behaves like a spring, as all gases do.

You can design a system (such as an airbox) where a ramming effect is achieved through tuning the size of the container to the resonance of the engine.

So can I take it that In The Shed disapproves of folk who restore a 970 Cooper S to factory specifications are not fully realising the potential of the 970?

I can't wait to hear how it goes.....

BMC not realising the 970's potential!