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distributor
- Thread starter kennethR
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Radford
Jedi Knight
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There is (in the Moss Cat) a replacement for the 25D4 dizzy, (which is the 45D4 dizzy) for about two hundred and five dollars. I am not sure that this is your best option though.
Question: Are you still running a single ZS carb on this car?
I'd really want to know what is "wrong" with the dizzy before replacing it. For instance many problems can be "fixed" by going with a Petronix system
Question: Are you still running a single ZS carb on this car?
I'd really want to know what is "wrong" with the dizzy before replacing it. For instance many problems can be "fixed" by going with a Petronix system
703MGB
Senior Member
Offline
First question. What carbs are you running:
Stromberg
Twin HS4
Twin HIF4
For the stromberg I have no recommandation.
For the SU it is easier.
1st stay away from MOSS for this you actually want to run a Lucas either 25D4 or later 45D4.
The most important thing here is the vacuum pick-up. On HS4 it is a ported one (on the carb side).
The best is an aldon distributor:
https://www.aldonauto.co.uk/aprods.htm
101BY1 A distributor with vacuum advance, designed to replace the original distributor on std. MGB's and Marina TC's, fitted with HS4 SU Carburettors. N.B. Later versions of these cars have the vacuum advance pipe connected to the inlet manifold not the carburettor, use 101BY2 for these applications.
101BY2 A distributor with vacuum advance to suit std. MGB's and Marina TC's when fitted with HIF4 SU carburettors. Improves driveability, while retaining the resistance to 'run-on'
As you can see the HIF4 carbs require a different distributor.
I think I saw that LBCAR stocks those items:
www.lbcarco.com
Once you have a new distributor I recommend also that you install the proper electronic ignition.
Finally if you have a set of HS4 I have a brand new 45D4 type 41427 that I could sell since I am not using it.
Stromberg
Twin HS4
Twin HIF4
For the stromberg I have no recommandation.
For the SU it is easier.
1st stay away from MOSS for this you actually want to run a Lucas either 25D4 or later 45D4.
The most important thing here is the vacuum pick-up. On HS4 it is a ported one (on the carb side).
The best is an aldon distributor:
https://www.aldonauto.co.uk/aprods.htm
101BY1 A distributor with vacuum advance, designed to replace the original distributor on std. MGB's and Marina TC's, fitted with HS4 SU Carburettors. N.B. Later versions of these cars have the vacuum advance pipe connected to the inlet manifold not the carburettor, use 101BY2 for these applications.
101BY2 A distributor with vacuum advance to suit std. MGB's and Marina TC's when fitted with HIF4 SU carburettors. Improves driveability, while retaining the resistance to 'run-on'
As you can see the HIF4 carbs require a different distributor.
I think I saw that LBCAR stocks those items:
www.lbcarco.com
Once you have a new distributor I recommend also that you install the proper electronic ignition.
Finally if you have a set of HS4 I have a brand new 45D4 type 41427 that I could sell since I am not using it.
dklawson
Yoda
Offline
Visit Marcel's tech pages at:
https://www.planet.eon.net/~chichm/tech.htm
The A- and B- series engines use the same distributors (basically) and according to the test work Marcel has done the advance curves designed for one aren't particularly different than those for the other. I've tried several different 23D4, 25D4, and Hitachi distributors in my A-series and there are differences on where the timing needs to be set to avoid pinging but beyond that the differences are hard to notice on a street machine.
That said, in answer to your original question, changing a distributor is a very easy process. First get a good donor dizzy and set it up with fresh points and condenser. Since it's not installed that's even easier to do because you can work at the bench. Next, read up on static timing either in your Haynes manual or on the web. Turn your engine over by hand until you've got the points opening to fire #1 cylinder. Remove the two bolts holding the Lucas clamp to the block, remove the old dizzy with clamp from the block. Transfer the clamp to the donor dizzy and put it back in, reversing the process. Set the static timing by turning the dizzy clockwise until you've got the points just opening (setting the static timing) then tighten the dizzy clamp components. Test drive the car and adjust the timing where you need it to be to avoid pinging.
I wouldn't think a 25D4 was "correct" for a 1979. You should have a 45D4, not that it matters. Something your mechanic may not be aware of is that you need to properly go through the carb adjustments AND the timing to completely clean up timing scatter at idle. You wouldn't think that one would influence the other but if they both aren't set right it will look like your dizzy or its drive gears are messed up when they really aren't.
The vacuum connections to the dizzy advance have never been clear to me on British cars. There is "ported" vacuum which comes from the carb body and there is "manifold" vacuum which is connected to the intake manifold. Ported vacuum is supposed to only kick in when when you're running at part or wide-open throttle as the vacuum is produced by air passing through the carb venturi. Manifold vacuum kicks in most at idle or when the throttle is almost closed. If there is a guide that explains which dizzy and carbs go together I'd love to see it as it would help me understand which dizzys get connected to the manifold and which connect to the carbs.
https://www.planet.eon.net/~chichm/tech.htm
The A- and B- series engines use the same distributors (basically) and according to the test work Marcel has done the advance curves designed for one aren't particularly different than those for the other. I've tried several different 23D4, 25D4, and Hitachi distributors in my A-series and there are differences on where the timing needs to be set to avoid pinging but beyond that the differences are hard to notice on a street machine.
That said, in answer to your original question, changing a distributor is a very easy process. First get a good donor dizzy and set it up with fresh points and condenser. Since it's not installed that's even easier to do because you can work at the bench. Next, read up on static timing either in your Haynes manual or on the web. Turn your engine over by hand until you've got the points opening to fire #1 cylinder. Remove the two bolts holding the Lucas clamp to the block, remove the old dizzy with clamp from the block. Transfer the clamp to the donor dizzy and put it back in, reversing the process. Set the static timing by turning the dizzy clockwise until you've got the points just opening (setting the static timing) then tighten the dizzy clamp components. Test drive the car and adjust the timing where you need it to be to avoid pinging.
I wouldn't think a 25D4 was "correct" for a 1979. You should have a 45D4, not that it matters. Something your mechanic may not be aware of is that you need to properly go through the carb adjustments AND the timing to completely clean up timing scatter at idle. You wouldn't think that one would influence the other but if they both aren't set right it will look like your dizzy or its drive gears are messed up when they really aren't.
The vacuum connections to the dizzy advance have never been clear to me on British cars. There is "ported" vacuum which comes from the carb body and there is "manifold" vacuum which is connected to the intake manifold. Ported vacuum is supposed to only kick in when when you're running at part or wide-open throttle as the vacuum is produced by air passing through the carb venturi. Manifold vacuum kicks in most at idle or when the throttle is almost closed. If there is a guide that explains which dizzy and carbs go together I'd love to see it as it would help me understand which dizzys get connected to the manifold and which connect to the carbs.
John Moore
Luke Skywalker
Offline
Rather than having my 25D rebuilt, I went with this. I'm very happy.
https://www.brittek.com/ultimateignitionkit.html
https://www.brittek.com/ultimateignitionkit.html
dklawson
Yoda
Offline
That's a very nice looking kit John. With all those parts being new or rebuilt it's a reasonably priced solution. I'm surprised, however, that the developers of that kit decided to stick with points instead of an electronic ignition module.
For more info on Lucas advance curves as they relate to A- and B- series engines, see the following link. It's a 12 page PDF. The succinct summary is that getting full benefit from a recurved distributor is only possible if done in concert with dyno testing for the exact engine involved. Sadly there is no "one-size-fits-all" distributor solution when it comes to performance distributors.
https://www.telusplanet.net/%7Echichm/tech/lucastuning.pdf
For more info on Lucas advance curves as they relate to A- and B- series engines, see the following link. It's a 12 page PDF. The succinct summary is that getting full benefit from a recurved distributor is only possible if done in concert with dyno testing for the exact engine involved. Sadly there is no "one-size-fits-all" distributor solution when it comes to performance distributors.
https://www.telusplanet.net/%7Echichm/tech/lucastuning.pdf
John Moore
Luke Skywalker
Offline
Doug, tho' it's not on the website, for a few bucks more you can get it with a petronix. I may ad a petronix someday down the road.
Hello all,
I was surprised when I read the introduction to this link:-
https://www.brittek.com/ultimateignitionkit.html
I have to totally disagree with the statement made. I run a 25D6, when it was overhauled, if ever, I don't know and I don't burn points up in 10,00 miles much less 2,000. It runs fine with minimal maintenance, wet weather does not affect it at all.
The basic wear issue with these distributors is the spindle bearings. When worn they give timing scatter. I personally wouldn't worry about the vacuum advance issue, but then I drive with my foot hard down.
Alec
I was surprised when I read the introduction to this link:-
https://www.brittek.com/ultimateignitionkit.html
I have to totally disagree with the statement made. I run a 25D6, when it was overhauled, if ever, I don't know and I don't burn points up in 10,00 miles much less 2,000. It runs fine with minimal maintenance, wet weather does not affect it at all.
The basic wear issue with these distributors is the spindle bearings. When worn they give timing scatter. I personally wouldn't worry about the vacuum advance issue, but then I drive with my foot hard down.
Alec
Thanks for all the advise. I found a 25d4 distributor at a local parts store. Only $66 dollar. I replaced it and the car runs perfect. Only problem I had was knowing that it is the 25d4 distributor and not the 45d4. Very easy process and timing was right on when I changed it.
SilentUnicorn
Yoda
Offline
Ken, You got a dizzy at a local parts store? for 66 bucks?? What store and where?
mark
mark
John Moore
Luke Skywalker
Offline
Mark,
I've heard of guys getting rebuilt 25 D's at parts store for cheap like Ken said, but the problem is, you don't get to pick the advance curve. They send you whatever they have on the shelf. As you know the 25 D was used in alot of different cars and there are many different varieties.
I've heard of guys getting rebuilt 25 D's at parts store for cheap like Ken said, but the problem is, you don't get to pick the advance curve. They send you whatever they have on the shelf. As you know the 25 D was used in alot of different cars and there are many different varieties.
Hello Mark, John,
a good point but easily rectified, just install the cam spindle and springs from the old distributor to the new one and you will have the original timing.
The new vacuum advance unit could well have different characteristics from the original so if that is still functional then swop that also, but I doubt if there would be any discernable difference from the driving seat.
Alec
a good point but easily rectified, just install the cam spindle and springs from the old distributor to the new one and you will have the original timing.
The new vacuum advance unit could well have different characteristics from the original so if that is still functional then swop that also, but I doubt if there would be any discernable difference from the driving seat.
Alec
dklawson
Yoda
Offline
I'm just spoiled. I like the easy starting of electronic ignitions be they Pertronix or other. However, I must admit that when problems arise with electronic ignitions... the first advice is ALWAYS to put the points back in to see if it will start with a standard ignition.
EDIT: I didn't want to mention another distributor possibility because I didn't think it was available yet. Please visit the following link to the MiniMania board and see the last page of this thread:
https://www.minimania.com/web/startreturn...1/msgthread.cfm
Marcel was developing a dizzy for the A-series engines that has four switch selectable advance curves. The company he was doing this work for was also developing other dizzys including curves aimed at the B-series engines. I don't know the specs on these dizzys yet but I will be looking into them as I trust Marcel's work implicitly. Feel free to follow the links to Marcel's sites in previous posts to this thread and send him emails. I'm sure he'd be happy to fill you in on this product.
Source for these A- & B- series dizzys:
https://www.123ignition.nl/
EDIT: I didn't want to mention another distributor possibility because I didn't think it was available yet. Please visit the following link to the MiniMania board and see the last page of this thread:
https://www.minimania.com/web/startreturn...1/msgthread.cfm
Marcel was developing a dizzy for the A-series engines that has four switch selectable advance curves. The company he was doing this work for was also developing other dizzys including curves aimed at the B-series engines. I don't know the specs on these dizzys yet but I will be looking into them as I trust Marcel's work implicitly. Feel free to follow the links to Marcel's sites in previous posts to this thread and send him emails. I'm sure he'd be happy to fill you in on this product.
Source for these A- & B- series dizzys:
https://www.123ignition.nl/
dklawson
Yoda
Offline
I was always able to start my Mini with points but I found it "easier" to start when I put the Pertronix Ignitor in the dizzy. It was even easier to start when I made the Hitachi distributor conversion. However, I must admit that the car has been kept in a much better overall state of tune since installing the Hitachi also. I'm sure that's part why the car is easier to start.