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MG MGB Technical - dizzy springs

having read peter burgess book on how to tune mgb engine I decided to do some basic checks after fitting K&N filters. I discovered that I only get 10 degrees mech advance instead of 20 degrees(+15 deg static). Stripped dizzy in excellent nick except for springs. Managed to find stronger small spring and replaced, what a difference! But still need to replace larger one. The question is does anyone sell dizzy springs anymore?
gary
gary roberts

Gary-
I don't know of any source for new distributor springs for the Lucas distributors. However, Aldon Automotive has been sucessfully recurving the spark advance on Lucas distributors for increased performance for as long as anybody can remember. They've developed a variety of spark advance curves for application with a variety of camshafts. Their formulas work beautifully. I have one of their recurved distributors on my engine, so I can personally endorse their product. Aldon Automotive has a website at http://www.aldonauto.co.uk/
Steve S.

Take at look at www.cambridgemotorsport.com where you'll find a product called the 'advance spring set'. It contains 3 large spings and two small. There are no instructions as the kit is multi purpose and can be used on any Lucas distributor. Its a case of trial and error to select the correct springs. It's about £10 including postage in the UK.
One thing puzzles me about what you say though - I thought the springs had to be overcome by increasing centrifugal force to provide mechanical advance. If that's so then by fitting stronger springs shouldn't you have seen a smaller advance than before?
Miles Banister

Miles-
Thanks for letting us in on the source. These springs are all but impossible to find!
Steve S.

Thanks indeed! Les Bengtson will be very glad to know of this source as will Paul Hunt. Cheers!
Bob Muenchausen

Thanks miles for the info on where to buy springs very useful. Yes it does seem strange at first, but peter burbess describes it this way in his book, if the mechanical cam is say 10 degrees,(most european chrome bumpers are) (20 degrees for the crank)with worn springs (slack or weak) then soon as the engine starts this slack will be taken up. In my case this amounts to 5 degrees which is half of the available mechanical advance! Restoring the spring means that when the engine starts and running at tickover, the springs should hold back the cam leaving all of the 10 degrees available as the engine speed increases. The aim being to use all the 10 degrees (20 degrees crank) at around 3000rpm.
If you have or can get hold of one of those dial in strobe lights it is easy to check. With the engine running at 1000rpm orless, and the vacuum advance dis-connected, set the static you need (in my case 14 btdc.) Then using the dial and increasing the revs in 500rpm steps, note the mechanical advance at each of the steps, and plot it out on a piece of graph paper. According to peter burgess the B engine needs something like 34 degrees advance (static + mechanical, in my case 14+20crank degrees=34 total) to effective burn the fuel at 3000rpm. It is important and as I have found makes quite a difference to the crispness of throttle response.

In my case it is a chrome bumper 24d4 dizzy, and the curves are slightly different for all the models. It is possible to obtain the required curve off the web, if you need to be really exact, but the above according to peter burgess is good enough for all fitted with the standard cam.
Hope this helps

Gary
Gary Roberts

Anglo Parts in Belgium also sells a similar kit of springs. Some of them are close or identical to some of the springs used on the later US spec cars. Using the kit will require "tweeking" of the springs, and the use of a distributor test machine, to duplicate the factory specified advance curve. It is possible to use the engine as a distributor test machine, if one has an adjustable timing light. But, this is not a particularly convenient way of doing things. It will work for a one off job, but would be somewhat inconvenient for general testing and experimentation. Les
Les Bengtson

Gary,

Ah I understand now - thanks. If you do get a set of those springs be sure to let us know how you get on with them.

Miles.
Miles Banister

All:

There was a tread in the past that said you could use the HEI distributor kit from Summit Racing and that the springs from it would work correctly.

http://store.summitracing.com/

Do a search on MOR-72300 for information. I will try to find the article on this to get which color springs the poster recommended.

Bryan
Bryan Prindle

Ok:

Here is the thread on the springs:

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Thread: Distribuitor springs
Posted 04 May 2002 at 14:21:22 UK time
Jack, Syracuse Wow, many thanks Clifton and Les for that tour de force.I wish that I'd never asked the question now.The only reason I did was that I seemed to remember some article talking about modifying or changing the weights, and I could not for the life of me figure out how you could do it simply by trial and error.My efforts in WORD are trial and error, but at least there is a go back facility, whereas this is a real tricky one.Your comments re the machines cleared the picture because I can see how the weights could be modified and then tested, whereas before it seemed impossible.
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Posted 03 May 2002 at 21:32:48 UK time
Les Bengtson, Arizona, USA, ragnar@aztec.asu.edu Jack. The weights are what, under centrifugal force, fly outwards and advance the timing by moving the distributor shaft in relation to the points. The vacuum advance mechanism moved the base plate and affects the relationship of the points in regards the position of the distributor cam. The rate of advance is controlled by the springs. The weaker the springs, the faster the advance comes on. There is, on most distributors, a cam arm which is stamped either 10 deg or 18 deg. This is distributor degrees or one half of the advance seen at the crankshaft. A ten degree cam stop will give you twenty degrees of crankshaft advance. Lightening the weights may allow them to move in a different manner, but, if they are too light, they may not be capable of moving the distributor shaft as far forward as it should. That is why most of us play with the springs and leave the weights alone. The cam arm can be modified as it is strictly a physical stop. By lengthening the cam arm, you stop it sooner. By shortening the cam arm, you allow more centrifugal advance to take place. All of this gets into advanced tuning and requires both a lot of trial and error experimentation and a distributor test machine to see what is actually happening when you make a change. For most of us, cleaning the distributor, installing a new distributor shaft bushing, lubricating everything and installing new springs are all that would be needed for a usable rebuild. Further work would have to be done based on a dynamometer/rolling road test. Les

Posted 03 May 2002 at 13:40:41 UK time
Clifton Gordon, NC, USA, flash1929@yahoo.com Jack, Usually the springs would be changed first, weaker springs= faster advance, stronger springs=slower advance. All Lucas advance weights I have looked at appear to be the same but I have neverweighed them. Since no one can find a source for spring information I would think the information on the weights is not available. You could remove some material from the weights by filing or grinding, removing weight should give a slower advance curve with a given set of springs or material could beadded for the opposite effect. In my opinion it's best to use springs to get the desired advance curve.FWIW, Clifton

Posted 03 May 2002 at 11:39:02 UK time
Jack, Syracuse Thank you Les Bengtson once again for your sterling efforts.May I ask anyone what part the weights play in this equation.If we are to interchange springs in order to modify dizzy performance, what do we have to do with regard to the weights.I was looking at some website last year, which I'm sure talked about having to modify the profile or something, of the weights, in order to modify dizzy performance in some way.Does anyone have any thoughts on this.?

Posted 02 May 2002 at 12:00:22 UK time
Clifton Gordon, NC, USA, flash1929yahoo.com Vic. In this thread count about 12 posts down and you'll see Paul Hunt's post, his web siteand email address is there. Clifton

Posted 02 May 2002 at 05:35:46 UK time
Vic Myers, Truckee California USA, Vemarooski@aol.com Matt Kulka- Who is Paul Hunt? How do I get to his site? Do you have his email. I've tried to get advance curves from Aldon, with no luck to date. Thx Vic

Posted 02 May 2002 at 01:12:41 UK time
Clifton Gordon, NC, USA, flash1929 Les; Interesting information. I would think some of the spring lengths may have streched overtime, it would be interesting to see how close each distributor is to original specificationsGreat work, thanks for sharing it with us. Clifton

Posted 01 May 2002 at 17:12:02 UK time
Les Bengtson, Arizona, USA, ragnar@aztec.asu.edu I have been doing some preliminary work on distributor springs, specifically as to what came in the factory distributors. I would still like to go through a few more distributors, but, due to the interest in this subject, have posted some of what I have found on my website. The article covers several of the distributors I have taken apart and inspected, the Auto-Zone rebuilt distributor I examined and the "Lucas 25D spring pack" from Anglo Parts. Go to http://custompistols.com/ then click on MG, followed by articles. The one you are looking for is "Lucas 25D Distributor and Springs". This may provide a starting point. Les

Posted 01 May 2002 at 14:15:31 UK time
Clifton Gordon, NC, USA, flash1929@yahoo.com I used the Summit kit and used the black, in my above post I said blue but that was an error.The black look to be middle sized springs. The combination of springs should allow you toget pretty close to the advanve curve needed. First I tried a gold and a black and it made the advance too quick. I was looking for about 32 to 35 degrees total advance at 3000 rpm and the black was close to that on my 41339 dizzy.Clifton

Posted 01 May 2002 at 06:56:12 UK time
Jared Snider, Oregon, USA, racingbrit@hotmail.com Dan,I didn't get the kit from Summit so I don't know if we have the same kit, judging from the colors, I'd say not. Mine came from a "Mr. Gasket" #929, the package says "fits GM HEI dist. with E-clips" The springs included are white, bare metal(but seem to have some red paint on the inside) and blue. I use the blue ones but haven't tried the others. Looking at the gauge of the wire used to make the springs, I think the blue are the middle sized ones. Don't take my word for it though as it's been a while since I've been that far down into the dizzy.Although now that I look at the back of this package I see a litle graph comparing the advance curves of the springs. The blue ones show 0 degrees at 1600 RPM then 5 degrees @ 2600 RPM then continuing to advance until it flattens out at 15 degrees @ 5000 RPM. The red springs(ok they were red after all) is shown to give more advance degrees than the blue while the white ones give less than the blue.FWIW, I knew there was a reason I'd kept this little package around for the last 3 years when I knew I'd never need any of it's contents again. Despite what others might say, being a pack-rat can be a good thing.

Posted 01 May 2002 at 04:17:35 UK time
Dan, San Francisco Summit Racing's part number SUM-G5212 was just delivered. It has three pairs of springs: silver-colored, gold-colored, and BLACK.May we assume that BLACK equals BLUE?

Posted 29 April 2002 at 18:29:55 UK time
Jack, Syracuse Are the blue springs the one and only springs to use or does it depend on the car?

Posted 27 April 2002 at 11:44:07 UK time
Alex , Edinburgh Wayne Pearson many thanks, I've just looked at the Summit Racing website and found the part.It seems that these may be the answer to our prayers.Has anyone else used them to good effect.

Posted 25 April 2002 at 17:58:22 UK time
Wayne Pearson, Virginia, USA, cwpearson@sprynet.com How about SUM-G5212 @ $4.50Wayne

Posted 25 April 2002 at 16:08:28 UK time
Alex, Edinburgh Summit Racing, advance kit for HEI dizzy, $4.50Checked the website and there were one or two which could fit the bill, but nothing at $4.50Clifton / Jared can you oblige with the correct part number so I can look at the correct part.Also does anyone know if Summit Racing has a UK branch for those of us over the other side.

Posted 23 April 2002 at 02:26:44 UK time
Clifton Gordon , NC,USA, flash1929 Jared; The blue worked for me, HC pistons and little bigger cam profile than stock.Clifton

Posted 23 April 2002 at 02:12:30 UK time
Jared Snider, Oregon, USA, racingbrit@hotmail.com I can second Clifton's suggestion. I was told by my parts guy to use the blue springs out of that kit. They seem to do the trick. I have not tried the other included springs. My motor is a high compression '67 that is closer to stock than it is modified.

Posted 23 April 2002 at 02:05:45 UK time
Clifton Gordon, NC, USA, flash1929@yahoo.com Summit Racing, advance kit for HEI dizzy, $4.50, throw all but the three sets of springs in the trash. Use the springs to set up your dizzy advance curve. Clifton

Posted 23 April 2002 at 01:32:15 UK time
Les Bengtson, Arizona, USA, ragnar@aztec.asu.edu Regarding the Auto-Zone rebuilds. They will sell you a distributor to fit most cars. I purchased one for my 68GT to find out what it consisted of. It consisted of a 72 distributor (advance curve) and an unknown vacuum advance can that is unlike any I have ever seen before. Totally wrong advance curve for my engine. On the other hand, the quality of the rebuild seems to be relatively good. Not a bad way to go if you need an early 70s spec dizzy and are willing to keep sending them back until you get the correct vacuum advance. Les

Posted 22 April 2002 at 23:45:15 UK time
Jeff Schlemmer, Minnesota, USA, qclimate@prodigy.net You can buy distributor re-curving kits for american V8s, If anyone had a NOS distributor I'm sure someone could compare the spring tension to those readily available through Summit Racing Equipment or Jegs. A phone call to either one would probably reveal a source.Jeff.

Posted 22 April 2002 at 22:21:24 UK time
Neil, Portishead, UK Okay, a bodge rather than a fix. But it might work.

Posted 22 April 2002 at 22:19:49 UK time
Neil, Portishead, UK, neil@neils-mg.fsnet.co.uk www.neils-mg.fsnet.co.uk MGOC, Moss, Aldon, etc, etc all sell 'new' distributors - hopefully all with the right springs. Aldon will make you a distributor with whatever curve you want (or need!). They must be getting them somewhere. If only they would tell us where.... has anybody asked them?Moss in UK sells 'uprated' springs. Of course, who knows what the specification is. BUT at least they are likely to be too strong (not enough advance) rather than too weak (too much advance too early = pinking). That would be a cheap temporary fix.Neil

Posted 22 April 2002 at 20:35:29 UK time
Maurice Blakey, Shrewsbury UK, blakeym@ukgateway.net I too came up against this brick wall a few years ago, I had a distributor which was fine except for the springs but finished up paying a lot more than neccessary for an exchange unit which may or may not have the correct springs. I have Lucas parts lists for these distributors but could not get springs anywhere.Surely if someone went to a spring manufacturer with a set of originals copies could be made, it should be quite easy on modern programmable machinery. Then we could all say "To hell with the rip off merchants" and at the same time be sure we have the correct springs. Maurice.

Posted 22 April 2002 at 19:29:37 UK time
Paul Hunt, Solihull, UK, http://www.mgb-stuff.org.uk paul.hunt1@blueyonder.co.uk As I've sad elsewhere just because a restorer restores distributors you can't assume he is using the correct springs. One I saw was an excellent mechanical rebuild, but it only had one spring, the cam was the wrong one giving the wrong max advance, and he didn't even attempt to hide the fact that the vacuum capsule was the wrong one. Buyer beware.

Posted 22 April 2002 at 18:05:48 UK time
Paul Kile, Fair Oaks, CA, gtv8@jps.net Ken,That is amazing - I never would have suspected that Auto Zone would have stocked much of anything for the MGB, let alone rebuilt distributors! I stopped going to the auto parts chains years ago, because I would always get a blank stare from the counter clones whenever I would mention MG. "MG - whazzat? Dontya mean GM??Cheers, Paul Kile

Posted 22 April 2002 at 16:33:14 UK time
Jack, Syracuse Ken, well done, that's great to hear.I think you are right saying look wide and far, rather than just call the usual guys.However, I wish someone knew where to get these springs, and maybe even the other bits such as weights, because if the restorers can get 'em, surely we can too.I accept that in your case, a new one was the answer, but for the average Joe who just wants to replace the springs, it sure is painful to throw away a good unit for the sake of....!Someone knows.

Posted 22 April 2002 at 14:45:31 UK time
Ken Lessig, Dallas, Tx., kenlanales@bigfoot.com Jack, sometimes you have to look in places other than the main suppliers; I just bought a (nicely) rebuilt 25D from AutoZone for $61.00. Checked the advance curve per Paul's site and it appears to be spot on. It's made a heck of a difference in the way my car runs, and has a lifetime warranty.

Posted 22 April 2002 at 14:35:04 UK time
Jack, Syracuse The two springs on the 45DM4 ( 1979) are identical, I have just stripped mine down, and they are pretty strong.Is there a conspiracy out there to prevent inexpensive distributor overhauls, or what.With all the other bits available for the MG, I would have thought it was a vital part to have, especially as an overhaul is usually never less than $100, or a replacement at $200.Somebody out there surely has a source for springs otherwise how would these restorers restore, and I can't believe they all independantly source the darned things.

Posted 19 April 2002 at 14:46:31 UK time
Matt Kulka, North Carolina, USA About those springs that seem in very bad shape: The 25D does have two springs of different sizes. I don't know for sure, but I think the 45D does also. When the motor's not spinning, the larger of the springs is loose on its pivots. This makes it look like the spring is stretched, but it's really not. If possible, have the distributor tested before replacing it. Paul Hunt's website has specs for distributor advance. He posts here often, and his web page appears next to his name.Matt K.

Posted 17 April 2002 at 23:34:55 UK time
Les Bengtson, Arizona, USA, ragnar@aztec.asu.edu Jose. The exact spring specifications for Lucas Distributors have not been published. Nor have full rebuild procedures, specifications and tolerances. Anglo Parts in Belgium has a five pack of springs for the Lucas distributors, but they are not always an exact replacement and are somewhat expensive. (About $25 US delivered.) If the springs are worn, other parts of the distributor may also be worn. The best thing to do, in most cases, is to purchase a new or properly rebuilt distributor. If you live in an ares which still has large numbers of the old, distributor equippped cars and mechanics trained and equipped to service them, see if you can find one with a distributor test machine. You can, using this machine, use springs from other distributors, on a "trial and error basis", to find a spring set that will work for you. Les

Posted 17 April 2002 at 20:48:37 UK time
Cecil Kimber, Abingdon UK >>Thanks in advancedistribuitor springs...get it? :)

Posted 17 April 2002 at 20:45:27 UK time
., . Harsh, but true.

Posted 17 April 2002 at 20:20:03 UK time
Chris Betson, Essex, England, chris@octarine-services.fsnet.co.uk; http://www.octarine-services.fsnet.co.uk No and you can't get them either!

Posted 17 April 2002 at 20:04:51 UK time
Jose Vargas, Bogota, Colombia, josevicente@musme.com I have a Lucas 45 D 4 distribuitor on a MG B engine and the springs are in very bad shape. 1. Does anyone know what are the technical specifications of the springs.2. Are the 2 springs the same ? If not please be specificThanks in advance,


Bryan
Bryan Prindle

Hello All,

I just got on the Summit Racing website and ordered the HEI advance curve kit. I ordered SUM-G5212, and the price listed was $4.50. However, the Handling charge was 7.95, brining the total to $12.95! We'll see if I can make them work and then determine if it's a good deal or not!

Cheers, Doug
Doug Keene

Doug. What will you use as your test bed? Do you have access to a distributor test machine or will you use the car's engine. What specification distributor are you attempting to replicate? I am attempting to gather as large a data base as possible right now. I hope to be able to get a dizzy test machine this summer. I purchased one something over a year ago, from a friend, and he has been kind enough to store it until I can get up to take possession of it. (Need I mention that this paragon of virtue is Bob Muenchausen? Most of the "old heads" would have recognised him from my description. Bob is noted for his many kindnesses. Plus, he has a new wife whom I have not met. This summer, for sure.)

In any event, if you can come up with data, ideas, possiblities, etc. please let me know what you are finding so that I can incorporate it into my, eventual, test series. Many thanks. Les
Les Bengtson

Les,

I don't have a machine, so will use the engine. I recently purchased a "Eurospec" distributor from Brit-Tek, and it turns out that it is a stock Non North American (Read U.K./Europe) 45D, 41610. I tested it by setting the static advance at 0 degrees, and then running the engine at various speeds to plot the advance curve. I know there is room for error due to my reading of the timing mark as it strobes, etc., but it came out quite close to Paul Hunt's spec for the 41610. The vacuum capsule also matches that of the 41610. The mechanical advance curve was much more conservative than I would like. I,m not sure why, but the I.D. sticker had been removed. As an aside, Chris Betson had mentioned that the 41610 is what you get if you buy a new 45D in the U.K.

So, what I will do is the same as I described above. I will put in a set of the springs and run the test at 1000, 2000, 3000, and 4000 RPM's, record the advance, and then decide which to use. Based on a posting by Clifton Gordon it sounds like the "black" set may be close to what I want. I currently have the car up on jacks. Just replaced the windshield, and am cleaning up some wiring while I have the dash out, so it will be a few weeks. I will post the outcome.

Cheers, Doug

Doug Keene

I used a timing light with a degree dial for setting up my distributor. The dial gives a more accurate reading, however, a timing light with a degree dial now cost $70 or more. I also used an automotive dwell/tach/voltmeter tester for rpm measurements. You can get pretty close but it's time consuming. The Summit springs are about the same length as stock Lucas springs, if you want an advance curve/line with
a step in it one spring will not be under tension until you reach the advance where the step is desired.
The eyes of the summit springs are too big to stay on the spring posts when not under tension, you can rebend the spring eye so it will stay on the post.

Marcel Chichak's web site has some very good information on how to set up a Lucas distributors. His advance curve requirements letter is also very informative.
http://www.planet.eon.net/~chichm/tech.htm

Another source of good distributor information is Des Hammill's "How to Build & Power Tune Distributor-type Ignition Systems" published be Veloce Publishing at: www.veloce.co.uk

Regards, Clifton
Clifton Gordon

Clifton,

Thanks for the input. I just looked at Marc's info, and it's excellent.

Doug
Doug Keene

This thread was discussed between 01/02/2003 and 07/02/2003

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