34 replies to this topic

[gaspen]

Hello

 

Many topics is about how bad are the old dizzys becuase of weakened springs and wear, as well as about the new dizzys "un-known" curves.

 

Therefore I decided to build a dizzy machine, not just for fun 

 

 

First things first : I need datas and I have to understand these datas

 

I found this chart : https://mgaguru.com/...ition/ig126.htm

 

Questions :

 

1) Assume that these numbers are measured at the dizzy's shaft, right ?

 

2) How should I interpret the vacuum codes ?

 

3) There is a 41026K in my 850. The list I've linked shows 41026A. Do these letters makes any difference on curves ?

 

4) Can I find more detailed advance curve data ? Maybe I can use the curves from the modern programable dizzys? 123ignition for example ?

 

Thanks

 

 

[68+86auto]

Ignore that chart unless it's as a last resort. It's full of errors, even the rotation direction isn't consistent.

Yes the degrees and rpm are at the distributor. Data for use in a distributor machine is listed like that. Workshop manuals are usually at the crankshaft.


Here's how to interpret the vacuum codes.
 Screenshot_20241116_202322_Opera.jpg   33.08K   3 downloads

The letters at the end can change the curves but not always.

Here's a better source of curve data however it's of little use to minis as it only goes up to around 1963. I have a newer book on it's way to me.

https://archive.org/...-specifications


I was making a distributor machine but gave up and found one for sale.
 IMG_20241116_201929_(2040_x_1150_pixel).jpg   54.29K   5 downloads

Edited by 68+86auto, 16 November 2024 - 10:32 AM.

[nicklouse]

IIRC AC Dodd was using a pillar drill and a rpm sensor to set the advance curves.

[gaspen]

Ignore that chart unless it's as a last resort. It's full of errors, even the rotation direction isn't consistent.

Yes the degrees and rpm are at the distributor. Data for use in a distributor machine is listed like that. Workshop manuals are usually at the crankshaft.


Here's how to interpret the vacuum codes.
Screenshot_20241116_202322_Opera.jpg

The letters at the end can change the curves but not always.

Here's a better source of curve data however it's of little use to minis as it only goes up to around 1963. I have a newer book on it's way to me.

https://archive.org/...-specifications


I was making a distributor machine but gave up and found one for sale.
IMG_20241116_201929_(2040_x_1150_pixel).jpg

 

Thank you

 

Wish I find such an equipment in my country 

[nicklouse]

https://youtu.be/3WJ...I8Pc-0E0aVTtyqq

https://youtu.be/wxX...vrhtUokgeOlS0J_

enjoy. 

[gaspen]

https://youtu.be/3WJ...I8Pc-0E0aVTtyqq

https://youtu.be/wxX...vrhtUokgeOlS0J_

enjoy. 

https://youtu.be/wxXJKI9MdIs?t=464

[Spider]

You can see my machine in this thread;-

 

https://www.theminif...d-distributors/

 

I've generally found the the springs last OK, even many I test now that are circa 40 years old are still in spec. however the other mechanical parts wear, causing the mechanisms to stick or over-advance.

 

The numbers on the distributor body dictate the curve, the letter suffix indicates a feature of it, eg, it might have a symmetrical or asymmetrical or high lift cam.

 

The various Lucas and BMC tables will state if the data is in distributor or crankshaft speeds and angles. Most are in distributor but not all, just check carefully before using it.

[68+86auto]

IIRC AC Dodd was using a pillar drill and a rpm sensor to set the advance curves.

 

The problem is it really doesn't tell you how many degrees advance it has. It's pretty crude. It doesn't tell you if each cylinder is firing at the same time either (bent shaft or worn cam).

[68+86auto]

Wish I find such an equipment in my country 

 

It's probably actually easier (but not easy) where you are. They are very rare here.

 

Saying that, I know a Hungarian mechanic who hadn't seen one before.

[ACDodd]

The problem is it really doesn't tell you how many degrees advance it has. It's pretty crude. It doesn't tell you if each cylinder is firing at the same time either (bent shaft or worn cam).



Hehe I love commented like this as it demonstrates a lack of understanding of the principles of the process I use. The amount of degrees is set before I get onto my jig. As is the straightness of the shaft.
I also have a design which my students make in which they build their own dizzy machine which reads out advance in both degrees and rpm. It also is a much faster to use that a conventional dizzy machine, as you don’t have to use the complete assembled dizzy to get the advance system to work. The reason why I don’t use this design is that I have developed a level of skill which means it’s not needed.
The next thing to consider is that advance numbers are different between engines. When you have worked on many hundreds you would know this, which is why knowing the numbers on a dizzy machine is less important that the numbers the dizzy actually delivers when it’s installed.

[gaspen]

The problem is it really doesn't tell you how many degrees advance it has. It's pretty crude. It doesn't tell you if each cylinder is firing at the same time either (bent shaft or worn cam).



Hehe I love commented like this as it demonstrates a lack of understanding of the principles of the process I use. The amount of degrees is set before I get onto my jig. As is the straightness of the shaft.
I also have a design which my students make in which they build their own dizzy machine which reads out advance in both degrees and rpm. It also is a much faster to use that a conventional dizzy machine, as you don’t have to use the complete assembled dizzy to get the advance system to work. The reason why I don’t use this design is that I have developed a level of skill which means it’s not needed.
The next thing to consider is that advance numbers are different between engines. When you have worked on many hundreds you would know this, which is why knowing the numbers on a dizzy machine is less important that the numbers the dizzy actually delivers when it’s installed.

 

Then the question : why they invented the distributor machine ? 

[gaspen]

 

Wish I find such an equipment in my country 

 

It's probably actually easier (but not easy) where you are. They are very rare here.

 

Saying that, I know a Hungarian mechanic who hadn't seen one before.

 

 

I searched it many time but without success.

[gaspen]

One of our local hero showed me this book 

 

 935f7dc9-f71b-475a-a998-0cc49e76d48a.jpg   43.99K   2 downloads

 ed8644da-584e-415e-9ee6-450c627c0c7c.jpg   89.46K   1 downloads

 2c279bfe-469f-44b7-b43b-81f2e3f70a46.jpg   91.87K   1 downloads

[68+86auto]

One of our local hero showed me this book 
 
935f7dc9-f71b-475a-a998-0cc49e76d48a.jpg
ed8644da-584e-415e-9ee6-450c627c0c7c.jpg
2c279bfe-469f-44b7-b43b-81f2e3f70a46.jpg

Those specs are at the crankshaft.

[gaspen]

 

One of our local hero showed me this book 
 
935f7dc9-f71b-475a-a998-0cc49e76d48a.jpg
ed8644da-584e-415e-9ee6-450c627c0c7c.jpg
2c279bfe-469f-44b7-b43b-81f2e3f70a46.jpg

Those specs are at the crankshaft.

 

 

Yes, I learnt it with google translator