9 replies to this topic

[Sterling M]

Hi,

I am rebuilding an Australian built (BMC badged) 998, wind up windows and quarterlight windows, 1967 vintage.

Due to local importing laws at the time, they used a locally built Lucas distributor, (29D).

It looks like the 29D was built for a six cylinder motor but there's not much information about this variation either.

Parts for these distributors are no longer supported (caps/rotors) and am considering my options by installing either the 25D or 45D.

My unit is reported to have an advance curve of counter clock wise: 14.5 @2000 RPM, 11 degrees @1000RPM and 1.875 degrees @ 450 RPM with no advance under 190 RPM.

I am having trouble deciding what model to go for which has a similar advance curve.

Does anyone have any information about the 25D or 45D distributors with regards to compatibility to the 29D curve?

TIA.

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[viz139]

British Lucas distributors normally have a 5 digit code starting  with 4 so  i checked 41052A and it comes up as a 25D6 , the 6 meaning it is indeed 6 cylinders.  Have you confirmed that there are only 4 lobes on this distributor and it is indeed correct for that car. I think there were only two choise of 998cc in 1967 , the 998 Cooper ( high compression) or the Elf/Hornet ( low compression). If your engine is standard the Elf / Hornet one may suit. I don't know how original you want to keep under the bonnet but the 123 dizzy is electronic with a choise of 16 curves selected with a switch inside.

[Tds76]

AYA0194 stamped on your distributor is the BMC/Leyland Australia part number for a 29D4 dissy for 998cc Minis & Mokes.

 

Rotor arms for the 29D are available here:

https://www.bmiparts...australian-29d.

 

There is some further info on Ausmini about it.

https://www.ausmini....lit=29d&start=0

 

 

Cheers, Paul.

[Sterling M]

Thanks Paul, interesting reading. Seems these dizzy's are renown for pinking and damaging pistons, which is what has happened to me, hence the full rebuild and investigating a way to avoid it happening again to the new setup. The 123 dizzy sounds the business but very expensive, is there another alternative out there that's worth looking at?

[Steam]

A 25D4 to suit would be a 41045 or 41057. The latter is a direct replacement for a 29D4 AYA0194 which is the one for a mk1 Aus 998 manual HC.

[Sterling M]

Perfect, thank you!

[68+86auto]

As parts are not available it is not worth keeping a 29d. Whatever distributor you use should have the advance curve checked, new distributors are usually a random curve and probably worse than a worn 29d. A 25d is the period correct replacement, a 45d is the newer distributor and will also work.

 

Even if a used distributor meets the factory advance curve it won't be optimum for modern fuels.

 

 

With the mini in that Ausmini topic started by me the melted piston is likely to be caused by a combination of things. The carburettor was/is also worn out and poorly adjusted. Since then, as I mentioned the springs were switched out (not by me) with random ones and the timing was not checked as I refused. I haven't updated that topic but as expected a while later it came back to me to be fixed as it was overheating. A "Professional" had checked the timing and said it was good but he "could not" check the dwell. When I checked it the dwell was at 50° which is far from the 60° specification. Upon rectifying that, the timing was also way too far advanced. I do have the values recorded and am meaning to update Ausmini on it. I was then told it was heaps better to drive however unsurprising to me the transmission failed the next day. 

[Sterling M]

Yes, I'm getting the impression the 29D has had its day and am looking for a replacement 25D with the correct casting numbers as specified by "Steam" above.

I have two in various stages of repair that have two different centrifugal advance limits (10 degrees and 16 degrees).

Hopefully if I can score the correct numbers, it should be a matter of giving it a birthday and checking with the timing light when installed.

I have given the carb a clean/check and have sorted the sticking plunger, hopefully that's on track.

The acid test is when I plug in my Innovate O2 diagnostic setup to tune the carb and road test it under load which should show up any further issues.

The model distributor no longer interests me as the curve is what I'm focusing on to achieve the correct results.

I think I have a 45D4 one somewhere too, but have left it out of the discussion as I know even less about it.

[timmy850]

Honestly I wouldn’t worry too much about getting an old distributor with the correct code. Distributors wear out over time, and modern fuel needs a different advance curve.

If you have the choice, I’d pick a 45D over a 25D for the simple reason that they are slightly newer. Get it checked on an advance machine so that it’s appropriate for your engine. You can mess around with springs and advance plates if you know what you’re doing and are able to measure the results

The spec in your first post is in distributor degrees, which is half of crank rpm eg:
14.5 @ 2000rpm (distributor) is 29 degrees at the crank at 4000rpm

Edited by timmy850, 10 August 2023 - 08:51 AM.

[Steam]

Just be aware that the chinese copy 45D4 off ebay and other places will need a lot of work before thsy are suitable for use.