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MG MGA - Exchanging Distributors

I have a 1960 MGA with original 1600 drive train and (worn) Lucas DM2 distributor. I have available to me a new Lucas 25D distributor presumably for an MGB. Is this a direct drop in replacement without getting into too many technical modification issues beyong the drive dog. Appreciate any advice ... thanks.
Michael Hosier

Michael
As you probably know the MGA1600 distributor was the Lucas 25D / 40510 (Moss P/N 1H811E)

The 1962-67 MGB distributor appears to have been a 25D / 40897. This number should be stamped on the side of the distributor.

I had the wrong distributor fitted to my "A" when I got it. Yes it was a 25D but speaking to Lucas Technical, apparently the mechanical advance was over twice what it should have been for an "A".

I exchanged for a correct 40510 recon unit here in the UK and things were a lot better I can assure you. So beware of what you have got there Mike.

Pete
Pete Tipping

I don't think the DM2 is available anymore. There is a fellow named Jeff Schlemmer that posts here a lot. He knows these distributors very well.
Rick Penland

The 25D is a direct drop in replacement, but the advance curve is likely wrong for your engine. The 25D came with anywhere from 9 to 23 degrees of advance. If you look under the points plate, the advance is stamped into the the timing stop. 12 or 13 would be great for your engine.
The rate of mechanical advance is also probably not correct for your car. If you post the model numbers on the distributor as well as the numbers on the vacuum advance, we can help you determine what that distributor was designed for and whether the advance curve will work with your car. Worst case scenario, I can recurve it for you!
Jeff Schlemmer

Jeff,
I hope you can help out Michael and I don't want to distract you from his question but could you address one for me?

I'm running a warmed up MGB 18V with 9:1 compression, Piper 270 cam kit, re-jetted (richer) MGA SU's, flowed head, stock MGA exhaust... and an Aldon 101BR2 distributor. I've been fighting pre-ignition knock.

Do you, or anyone, know if that would/could be due to the Aldon's advance curve? By the way I run California's 91 octaine fuel and the knock is reduced by octaine-boosters.

At this point I'm considering spending some bucks on a Safeguard Electronic Ignition/Knock Retard system (www.american-pi.com/Safeguard). Thanks
Steve
Steve Meline

Pete, I have always assumed that the MGA dizzy was always a DM2 and the MGB's were 25D or 45E from manufacture but you incdicate that the 1600's used 25D from the outset ??
I know that there are issues with date codes and all but as for strictly model type the 1600 was supplied with a 25D ... is that correct ??
Michael Hosier

Michael. I have owned two 1961 MGA 1600 cars. Both came with the DM 2 distributor installed, which seems to have been original to those vehicles. The first was given to my brother when I was transferred to Germany and he and my father restored it. The second was purchased in 1978 when I came back to the US to attend Squadron Officer's School and needed a car for that period. I still own it and have been in the process of taking it apart for a frame up restoration. I have direct knowledge of both cars since 1975 and both engines seemed to have been as delivered from the factory. The fact that both engines had the DM-2 distributor, with the same specification number, leads me to believe that the information in the factory workshop manual is correct and that the DM-2 distributor was installed in the MGA 1600 as standard.

If someone has an MGA 1600 with a Lucas 25D4 distributor, it was probably installed after the car left the factory.

As to what to do in your case: Before I decided to use an MGB engine as part of my restoration, I compared the Lucas 25D4 distributor, specification number 40897 to the MGA Lucas DM-2 distributor. My impression was that the 25D4, 40897 as used in the early MGB high compression engines (up through 1968) should be a direct replacement for the DM-2 distributor of the MGA 1600. Minor timing adjustments might have to be made, but, this is true of any distibutor in any engine.

John Twist, of University Motors Ltd can rebuild your current distributor back to factory standard condition should you decide to do that.

Les
Les Bengtson

Steve

Check out the J&S web site at http://www.jandssafeguard.com/ as another possible source.

FWIW

Larry
Larry Hallanger

Les, the one thing I have noticed is that a few of the late 1600 DM2s actually came with the shaft and centrifugal advance assembly of the 25D. I always figured that they ran out of stock on the DM2 shaft assemblies and still had quite a few bodies left to burn up.

Steve, shoot me an email. I ran the same Aldon distributor for a while. It never performed for me the way I thought it should, and that's when I tried about 10 different ignition curves on my car (and at least 20 more on the bench). The knock you have could be from the distributor curve, an ignition short, sharp edges in the combustion chamber, spark plugs, cooling issues, or probably a handful of other places.
Jeff Schlemmer

Pete, the 40510 is a DM2. The Moss replacement may be a 25D?
Jeff Schlemmer

Michael,

I've been down this route for Twin Cam distributors also. A point worth nothing however is:

The fuels (Gas in the US) we now all use is quite different to that which the engine was designed for.

So chasing the exact original advance curve is almost a futile exercise these days.

Also the chances your head has been milled at least once raising the compression is also quite high.

There was a guy on eBay a few weeks back who had the original springs available, which would at lease bring your old distributor more inline with what it once was.

Hope this helps.
<MARK>
Mark Hester

This thread was discussed between 08/03/2006 and 10/03/2006

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