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PostPosted: Mon Apr 01, 2024 2:42 pm 
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cooperess wrote:
I have already fitted the 23D4 40718F MGA distributor and it works.

Just wondering if is Ok to install weighs & springs from my AYG0175 29D4 into 23D4 40718F.


Does it advance? Has someone changed the internals already?

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PostPosted: Mon Apr 01, 2024 2:57 pm 
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cooperess wrote:
I may have rocks in my head but thought if I put the right bits in another body then it should work like the original even if they are old and worn.

There’s a slim chance it’ll work, but unless you check and measure you’ll have no idea

And as mentioned above, the MGA distributor you’re using now is a clockwise rotation distributor. Using it in a mini will mean you get zero advance across the rpm range and it’ll run poorly compared to a properly curved one (at least from my quick thinking now). They also use an asymmetric lobe to drive the points

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PostPosted: Mon Apr 01, 2024 3:17 pm 
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If MGA distributor ran clockwise that would mean the firing order would be different but it's not, so it must be running anti clockwise.


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PostPosted: Mon Apr 01, 2024 3:59 pm 
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The “advance cam” on the distributor has 4 lobes to actuate the points. This needs to be run the correct direction for best results

The advance cam has an arm which sets the maximum advance. In this photo it’s stamped 17 degrees which means it’ll add a total of 34 degrees at the engine. If you span this backwards I think it’d stay stuck on the base timing and not advance. The springs only work one way? Or perhaps the centrifugal action is the same either direction, I need to think a bit more !

They definitely use different rotor buttons for CW vs CCW

(This cam was modified to reduce the distributor timing)


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Last edited by timmy201 on Mon Apr 01, 2024 4:10 pm, edited 2 times in total.

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PostPosted: Mon Apr 01, 2024 4:03 pm 
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Steam wrote:
cooperess wrote:
Is it Ok to transfer the internals of a AYG0175 29D4 to a 40718F 23D4 distributor and use it on my Mk2 as parts for 29D4 are impossible?

Any thoughts would be great.

A 23d with serial number 40819 is a direct replacement for AYG0175 and has an identical curve. That would solve all your problems easily.
Whether the springs and weights from a 29d will fit in a 23d is only part of your problem. If I am correct the 40718F is from an MGA and is a clockwise distributor. The A series needs an anticlockwise unit.


You are correct, as confirmed by Marcel Chickak's voluminous listing.


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PostPosted: Mon Apr 01, 2024 8:38 pm 
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Steam wrote:
If I am correct the 40718F is from an MGA and is a clockwise distributor. The A series needs an anticlockwise unit.


I just thought about the direction issue. This will solve a lot of confusion which I also contributed to before thinking of this.

The commonly available PDF of distributor specifications seems to be full of errors. I can't give that PDF a name as I don't know the original source and it is available on many websites, also in reformatted versions.

The PDF lists minis as CCW but the MGA as CW.

It appears that the MGA distributor is actually CCW as we usually call it.

Lucas officially specifies the direction as if you were looking from inside the engine. Lucas therefore specifies minis as CW distributors.

I believe that PDF is made up of a mix of information, it isn't from one source and is why a lot of information is missing.

It's likely that some of the sources referred to from outside the engine whereas others used the Lucas terms.

For example that list specifies many Jowetts (where it is even specified) as CW yet they actually turn the same way as a mini. I have a mini distributor in a Jowett Jupiter which according to that list is CW and the mini CCW.

When I look for MGA distributors on eBay etc they all appear to turn the same direction as a mini.


I have had many issues finding distributor data, especially when using that PDF. I recently purchased a 1960s distributor specifications book by Vane which will arrive soon. I will scan it in.


The short version is that I now believe both an MGA and a mini distributor turn the same way.

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1986 Mayfair (998 auto), 1974 S, 1974 Van, 1972 PMG Van

Too many minis


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PostPosted: Mon Apr 01, 2024 8:47 pm 
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timmy201 wrote:
If you span this backwards I think it’d stay stuck on the base timing and not advance. The springs only work one way? Or perhaps the centrifugal action is the same either direction, I need to think a bit more !

They definitely use different rotor buttons for CW vs CCW

(This cam was modified to reduce the distributor timing)


As per my previous reply it is most likely irrelevant but I'm now thinking when turning the wrong way it would retard but at a different rate to the advance in the correct direction.

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1986 Mayfair (998 auto), 1974 S, 1974 Van, 1972 PMG Van

Too many minis


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PostPosted: Tue Apr 02, 2024 9:38 am 
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DavidE wrote:
Steam wrote:
cooperess wrote:
Is it Ok to transfer the internals of a AYG0175 29D4 to a 40718F 23D4 distributor and use it on my Mk2 as parts for 29D4 are impossible?

Any thoughts would be great.

A 23d with serial number 40819 is a direct replacement for AYG0175 and has an identical curve. That would solve all your problems easily.
Whether the springs and weights from a 29d will fit in a 23d is only part of your problem. If I am correct the 40718F is from an MGA and is a clockwise distributor. The A series needs an anticlockwise unit.


You are correct, as confirmed by Marcel Chickak's voluminous listing.

I am not correct as it turns out. I apologise for derailing the thread.

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