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MG MGB Technical - 'Racing' Distributor ?

O.K. , my extremly eccentric millionare buddy gave me a distributor yesterday , claims it was in his buddys racing MG some years ago - it has the folowing numbers stamped into it just like I write them here

40718 A
23D4 460

What is it ? he suggested timing it to 2 DBTDC at 600 RPM's , I have not yet installed it pending your responses .

My car is runnning well (!!finally!!) in it's stock form but I am interested in this item _if_ it will help .

TIA ,
-Nate
NSH

Check Paul Hunt's website. If it ain't there, it probably ain't MGB.
Ken R
Ken Rich

A racing distributor will normally have no vacuum advance and is not recommened for street use, as milage suffers and damage can be done to the engine if you get lazy and don't shift down soon eneough when accelerating from low RPMs. If it is running well, it is unlikely that changing the distributor will be an improvement.
George B.

Nate. It is very hard to beat the stock, factory specifications without putting a car on a dynamometer/rolling road and finding out EXACTLY what advance curve is ideal for that particular engine. The term "racing" covers a multitude of activities related to driving cars fast in competition. Some of these activities are performed with street cars and the information developed may have street application. Other forms of this, as George B notes, bear little relation to street use and the modifications peformed will not be useful on a street car and may actually decrease its street performance. As to your distributor. Go back to the thread from last week, the one on distributors, and look at the website I gave you then. It will tell you, if possible, the original application for your Lucas 23D4 distributor, specification number 40718S built in the fourth week of 1960. (Please note, some sources believe that the first number of the three or four digit date code refers to the MONTH of manufacture. The sources I have consulted have stated it refers to the WEEK within the year. I have two items of Lucas manufacture which have a date code having the first two digits higher than 12. Take your choice as to which you prefer to believe.)Les
Les Bengtson

Thanx , les ;
I wasn't able to find that dizzy info , I'm still learning how to cut & paste addy's plus this is a low bid POS computer so I'm restricted from various endevors (like e-mailing any of you directly) .

John Twist (seems like a nice guy) says $200.00 (ouch) for a correct 1967 dizzy .

I'd really rather keep it stock if at all possible as I'm quite likely to kill myself if I get too much power under me . plus in the long run I find it simpler to maintain .

-Nate
Nate

Nate. The website mentioned shows the Lucas specification number 40718 to be a Lucas 25D4 and states it was used on the 59-61 mga twin cam. Do not know if the Lucas 23D4 was a centrifugal advance only dizzy for this same specification. But, you may have mis-read the number, the website may be wrong (I found one dizzy listed as a 71 Sprite, but have a dated 67 example of that spec in my collection), or whether it really is a 23D4 for the Twin Cam. Les
Les Bengtson

Don't know if it is an unbreakable law across all serial numbers but my Lucas Parts List shows the 23D4 as having no vacuum and the 25D4 as having vacuum.
Paul Hunt

The numbers I posted are _exactly_ as they appear on the side of the dizzy , including the spacing .

-Nate
NSH

Gentlemen-
I quote from Clausager's "Original MGA": On later Twin Cam cars, from engine number 2223, the DM2.P4 distributor was replaced by a type 23D4 which was not fitted with a vacuum advance."

NSH-
Looks like you've got a distributor that's about as hard to find as they come. Twin Cam parts are very rare and very expensive ($$$$)! Sell it to a Twin Cam owner and you'll easily be able to buy at least a stock new Lucas 25D4 distributor, spark plug leads, and a high performance coil.
Since you're looking for a bit more performance, I'd highly recommend a Lucas distributor with an Aldon-modified spark curve. If you're still using the SU HS4 carburetors and stock camshaft you should order distributor 101BY1. If you've converted to HIF4 carburetors, order distributor 101BY2. If you're running a Piper 270 or 285 camshaft, oder distributor 101BR2. Aldon Automotive has a website at http://www.aldonauto.co.uk/
Steve S.

Thanx , Steve :
As it was a gift I will try it but if I do not like it I will must needs return it to my buddy .

My car is fairly stock , HS-4's on a late 1800 low compression (??Marina??) engine , only the low restriction exhaust is not stock . I will try this and see what happens , thanx for the other supplier tip .
-Nate
NSH

NSH-
If you're going to run that centifugal-advance-only distributor on the street, keep an eye on your temperature gauge. Those things tend to make the engine run hotter and have been known to occasionally fry valves! The effect on ignition advance is much the same as driving with a wide-open throttle all the time. Expect fuel consumption to worsen, too.
Steve S.

This thread was discussed between 19/02/2002 and 22/02/2002

MG MGB Technical index

This thread is from the archive. The Live MG MGB Technical BBS is active now.