Morris Minor Owners Club

Mike those photo's look familiar, I think the top ones, the green ones, are from Scott
here is OZ I think and the bottom one looks like my gear when you where here in Brisbane.

The dizzy is electronic and the reason is that when I went to get it converted the fellow
said the original one was not deep enough in the body to accomodate the electronic gizmo's
so he converted the later series II. But apparently the vacuum is not nescasary as the original
never had it anyway.

You could equally say the second carb and modified exhaust are not necessary as they weren't fitted originally.
The reason later cars had vacuum units fitted is that it fits the ignition curve to the requirements of the engine better.

Well, vac advance exists to aid economy at low throttle settings plus help the igniting of weak/econ mixtures. At idle you have lots of vacuum and this will advance the timing a lot but at full throttle you'll have zero-ish advance from the unit. Just off of idle (say, 1000 rpm?) you'll have either lots of vac or less if the location of the port is in the manifold (downstream of the butterfly) or just before the butterfly. I'm not 100% up on the technology here but the short version is that the 25D4 will run best if the vac advance is plumbed in "to the same location as it was on the engine it came off of". If it expected lots of vac advance just off of idle then it would've had weights for a small mechanical advance just off idle. Remove the vac input and you'll have little advance just off of idle and it will run like a pile of poo. Ring any bells?

Does this make sense?????

On the Srs2 it may well be plumbed in to the raer of the carb, on the flange, just below the throttle spindle where it is seeing a different vac from the manifold on the other side of the butterfly in the manifold.

Hello Oliver,
If the engine is idling much too fast it is certainly getting a supply of air that is not controlled by the throttles (assuming you have followed the other suggestions and you know the throttles close properly). This suggests an air leak into the inlet system and I see something in this picture that has my attention - What is that tube below the air inlet casting?[frame][/frame]
Is that connected downstream from the carburetors? It won't matter if it's upstream, it may be only a drain. If that is not the culprit I would examine all the gaskets between the carburetors and the manifold and also the manifold gasket itself. Is everything tight? Are the throttle shafts a good fit in the bodies? I can't see a throttle shaft air leak giving you 1600 RPM but it could screw up the idle speed more than you might think. Also, with two throttles connected as you have them if the alignment of the shafts is off by even a little they will bind. I have experienced this problem with my car.[frame][/frame] even though the shafts are joined by a flexible connection.

Good luck with it, that is certainly a pretty engine compartment in a very attractive car.

Darrell McDonald

Have you followed precisely the instructions for tuning twin carbs? If you have not got the instructions I can send you some.

I've just got to say I have been extremely "time poor" lately
or I would have dedicated more time than I have to getting the
engine running better.

Once again my good mate Neville came over to try and sort things out, with me, so thanks Nev.

I only had 3-4 hours to work on the car.
OK, before we started again, we checked the twin carbies and found that
the springs were missing from the pistons. So we replaced them then we made sure the pistons moved freely. Checked the linkages.

Because we were down on vacuum on the front carb, I thought I still may have a valve problem.

So we started it and warmed it up, then removed the plugs and did a compression test. a couple of the pisons were down a little, but nothing to warrent the low vacuum.

Then I noticed water leaking from the back of the head, so we re torqued the head bolt and fingers crossed they are not leaking.

So the next thing we did was to take the carbies off and check everthing off the car.

It was OK, but I notioced that the high vacuum carb's butterfly was "ever so slightly" open more than the other when "closed." I figured that maybe the manifold may be not quite flat which was twisting the accelerator shaft when bolted on. So there was still further adjustment on the shafts once installed so we re set the butterfly valves and "TA DA" we got a decent idle speed!

Then we went about trying to fine tune the carbies and timing, but by this stage we where rushing a bit as we were on over time, and then the engine cut out and would not restart.

We soon realised we had run out of petrol!
So I think that was a sign to down tools and come back later.

But I am very happy with the results so far, so thanks agin to Neville for all his help.

It looks like I "MIGHT" make it to the Australia Day Celebrations on the 26th Jan.
But past dates ahve come and gone so we shall see what we shall see!

You have to undo the clamps on the thottle linkage so that both carbs are tuned independently and one does not affect the other.

Well I am very happy to say Neville and I
sorted it out & I went for my first drive today!



It was a combination of carby setting and timing.

So far so good!

Hi Oliver,
Did you make it to Australia Day Rally?