15 replies to this topic

[blacktulip]

how can you tell a cooper s 25d dizzy from a normal 25d dizzy?

[bmcecosse]

It has no vacuum advance. At the time - this was the 'thing' to do - run with no vac. We know better now!

[blacktulip]

so any 25d with a vac advance it not the s version?

[jaydee]

As far as i know, old S engines never used vacuum advance..

[Ivor Badger]

The part number stamped on it is the simple way.

[minimender]

Have a look on the advance plate it will have the advance degrees stamped on it. I'm not sure whether all the 'S' models used the same dizzy but if the number is larger than 10 then it would be safe to say that it isn't an 'S' part.
I'll look it up if no one knows off hand.

[bmcecosse]

The lack of advance is the answer - although some basic van models didn't have advance either! There is a part number of course - I just can't remember it now - and it's too cold to go out to the garage and look at the S dizzy I have there! But why the excitement ? It wasn't otherwise 'special' in any way - although stronger sprung points were specified for the S engines.

[minimender]

The lack of advance is the answer - although some basic van models didn't have advance either! There is a part number of course - I just can't remember it now - and it's too cold to go out to the garage and look at the S dizzy I have there! But why the excitement ? It wasn't otherwise 'special' in any way - although stronger sprung points were specified for the S engines.

It's because it's off an 'S' everything from the 'S' makes yer Mini go faster....not.

The Morris Marina was very similar and had no vac advance for some reason , something to do with crank rumble problems I believe.

[dklawson]

As Roy said, the -S had no vacuum advance. The family of distributors was the Lucas 23D4 (as opposed to 25D4 with the vacuum canister). The base number for the -S distributor will be "40819"

[bmcecosse]

That's the number I was looking for! Well done. Since we are on the subject - does anyone know what mechanical advance was built into that dizzy ? I robbed the bits from mine years ago - to put in a dizzy WITH vacuum - and it's long gone now.

[minimender]

That's the number I was looking for! Well done. Since we are on the subject - does anyone know what mechanical advance was built into that dizzy ? I robbed the bits from mine years ago - to put in a dizzy WITH vacuum - and it's long gone now.

Depends on which 'S' it was taken from.
the static figures might help you as they advanced from that to about 30 degrees
The 1071 was 12 deg static
The 1275 was 2 deg static
These figs would suggest a lot of built in advance so prob a 15 deg dizzy

I know the last 'S' models used a 10 degree dizzy but they had vac advance.

Hope that is of some help.

[blacktulip]

cheers chaps, i have looked it up and it turns out its a 998cc cooper dizzy (up for sale if anyone is interested)

[minimender]

cheers chaps, i have looked it up and it turns out its a 998cc cooper dizzy (up for sale if anyone is interested)

Good dizzy for a 998 that, set it up at 5 deg BTDC static as it was in the cooper and it will go well.

[dklawson]

Roy, if you're looking for the mechanical advance cam info on the 23D4, check out this PDF spreadsheet by Marcel Chichak:
http://www.starchak..../pdfs/lucas.pdf

Search the PDF and you'll find three 40819 dizzys includes some data on their advance curves. Marcel also has a PDF on tuning the Lucas dizzy and it has more information on the 40819 advance curve and components:
http://www.starchak....lucastuning.pdf

[62S]

I know the last 'S' models used a 10 degree dizzy but they had vac advance.

The last S distributor was the 41033 but it still didn't have a vacuum advance.