Hi all
I think my S is pinging and have been reading up on the problems as what could be causing it, have been told to check the dissy is operating properly.
I'm not sure what sort I have and what sort I should have all I know is it doesn't have vacuum advance, is this correct and how do I go about rebuilding it.
What do I need to look for
Thanks in advance

MK1 S 23D4 and the MK2 S 29D no vac internally are very similar and have the same slow advance curve and a 15deg advance plate inside the dissy. The total crankshaft advance is 30deg. If you set your static advance any more than around 6 degrees you may get pinging. There is a simple mod if your handy with a welder and have an accurate timing light. Or do what everone else is doing now and go the black box.

Here is a picture of what I did to mod my 23D4 dissy. Easy to pull apart. Just punch out the drive cog pin and the rest comes out the top.

Check for bush for wear which will change the point gap and the dwell.

MK1 S 23D4 40819H and MK2 S 29D AYG 0175 Lucas dissys.

Or you could do what I did and install a Accuspark dizzy and Black box

mine would ping like crazy i found it did it at different rev ranges so by installing the black box i van now adjust it so that i get the right advance at the right time

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1968 Morris Mini Cooper S

Here is the info I have collected on the Cooper S distributors.

MK1 Cooper S
The Lucas 23D4 40819B was used with the original AEG148 cam (used up to engine No 9FSaY 40006)
The Lucas 23D4 40819H was used with the later AEG510 cam.
There is only a minor difference in the advance curve at low rpm. The 40819H has about 2 deg more advance at low rpm but the tolerances are such that the advance curves overlap any way.

MK2 Cooper S
The 29D AYG1075 was used from 1969 on the 9FXEY engine.
The first 70 Police MK2 Cooper S SPO41 got the standard AYG1075.
After the first 70 SPO41 police cars they went to the AYG0272 and that was also used on police Clubman GT’s. These had different points, springs and advance weights.

(The MK1 S 23D4 P/N 40819H and the MK2 Cooper S and GT 29D4 P/N AYG0175 both had the same curves.
Engine RPM = 650 rpm 0 - 2 deg, 830 rpm 4 - 8 deg, 1000 rpm 8 - 12 deg, 4000 rpm 18 - 22 deg, 7000 rpm 28 - 32 deg.)
The 15 degree advance plate does not work very well in a modified engine with modern fuels. Most engines will want a max advance of 32 degrees and an idle advance of 12 degrees. The 10 degree plate is more appropriate and will let you run the higher idle advance without the engine pinging at max rpm. More idle advance helps with economy and power.

I have a MK2 dizzy AYG0175 with a date stamp of 10 68

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That's why it's good to be.............ME

Probably fitted to a late Mk1 S in early 69. Not sure about the time lag on parts fitment. My car has dates from early 68 to late 68 and is a 5000 car.

I have an original mk I dissy.I found the same as others that it pinged like crazy in the midrange and if you retarded it the performance went. I had it checked by locAl classic car mechanic (ex BMC trained) on dissy bench tester it was all over the place. He advised it was very difficult to find correct springs and time consuming to test. Not only that but one of the cams for the points were out by a degree. That's 2 degrees at the motor!!!!

I wanted to keep to original correct dissy on the car. By far the best option i found is a stealth black box as mentioned. The weights shown above are disabled by tying them off with wire and the black box takes over their job. The mechanical points are replaced with electronic ignition. The perfect curve for the car can the be programmed in using a laptop. The box and wiring can be all hidden, and it all looks 100% original.

The car has never run so smoothly or returned such low fuel consumption.


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68 Morris Cooper S Mk1 (*ex 78 1275 LS 4th last built, 70 Morris 1500 OHC & 70 MiniMatic)

Thanks everyone I guess I need to find out what sort I have and if philp is right it can't be rebuilt so might have to go the black box way, can someone give a $ value for this and where to get one and any info as I'm not very good with this sort of thing......thanks again

Send a PM to `convertible mini' on here. He is an auto electrician in Brissy, and sells them.
Cost is around $200.

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DrMini- 1970 wasaMatic 1360, Mk1S crank, 86.6HP (ATW) =~125 @ crank, 45 Dellorto (38 chokes), RE282 sprint cam, 1.5 rockers, 11.0:1 C/R.

For the go to wo solution think $350.00 from "Convertible Mini" it is actually very easy to setup.

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1968 Morris Mini Cooper S

They can still be rebuilt as per original with mechanical weights springs and points ...and I can understand some would prefer this for originality. But it is getting harder to find correct springs ...and the black box is a great solution that is completely reversible.




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68 Morris Cooper S Mk1 (*ex 78 1275 LS 4th last built, 70 Morris 1500 OHC & 70 MiniMatic)

Thanks Doc and Phillb for your help, can you buy a new dissy or rebuild kits or is it best to go with black box

Talk to "convertible mini" as Doc suggested. Do you want me to pm you his details?

Yes, you can buy new reproduction distributors but they won't look right for your S. You also run into the same problem of not knowing what the advance curve is like unless you buy the very expensive ones. Even your original Cooper S distributor when new could be improved to run on the fuel we use today.

The option of an electronic module (replace the points) and some kind of programmable advance (like the Blackbox) mean that you can get the timing near perfect for your car.

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Convertable mini has both new replica mk1 dissys (I think) and the black box.

Depends what u want.

If you want absolute originality then the rebuild the dissy with weights and points.

If you want to keep the appearance of original dissy on the car I'd go with the black box. You just need to check shaft is ok but can be easily rebushed.

If you are happy with a new replica Mk1 dissy or a aftermarket dissy then those options are also there.




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68 Morris Cooper S Mk1 (*ex 78 1275 LS 4th last built, 70 Morris 1500 OHC & 70 MiniMatic)