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MG MGB Technical - 123 Distributors

Has anybody had any experience with the 123 distributors supplied by TDC Performance <>? They are apparently an electronic distributor with switch selectable advance curves and vacuum acvance. Cheers - Dave
David DuBois

Seems like a well thought out product...the installation guide is 1st rate. I'll be interested to know how they perform. Since I just had my 25D rebuilt by John Twist I won't be needing a dizzy for years...
Robert Dougherty

How much does it cost? My guess is that it would be much cheaper to have a stock unit rebuilt and recurved, then add on an electronic conversion kit.

I wonder if they actually have a mechanical advance, or if its just an electronic program to simulate the advance curve? That would eliminate many moving parts and necessary maintenance...
Jeff Schlemmer

This product was discussed in an earlier thread. Apparently it has a solid state pressure transducer to accommodate the vacuum advance input. Believe that the rpm curve is a programmed function.

75 TR6
ex 73 B
B.J. Quartermaine

There is a thread on the 123 distributor in the archives.
The price is $425 Canadian, or around $375 US.
It has no mechanical advance, it's all electronic. If you email TDC Performance for information the email goes to Marcel Chichak. Marcel has written several ignition articles and made a PDF file of Lucas distributors.

A new Lucas 45D, with an advance curve that fits all, distributor is around $200, add the cost of re-curving to your vehicle and a pertronix Ignitor and you are going to have close to $400 in the distributor. An alternative choice is the DUI distributor for the MGB. It's a big unit and sure doesn't look original. The main advantage I see with the DUI is you supply your engine data to them and they curve the distributor for your car. It uses a racing version of the GM HEI module. If a DUI distributor fails on a weekend drive you can repair it with HEI parts from Advance or other parts discounters. The DUI is also around $400. If a 123 distributor fails, you pull out the old Lucas to get you home and call TDC for replacement parts.

The March 2006 issue of Classic Motorsports has an article "Zap It" by Carl Heideman. They show dyno figures on a rubber bumper MGB OE distributor, a new 45D with points and 45D with ignitor. The OE distributor had 19.9 rear wheel hp @ 2000 rpm, 60.4 hp @ 4500 rpm. A new distributor with points was 23.8 and 56.6. The new distributor with ignitor had 23.8 and 60.4. The new distributor produced less hp than the OE distributor from 3500rpm and higher.


Clifton Gordon

The DUI unit is a 4cyl version of the HEI distributor as used in Buick, Olds, and Pontiac (not Chevy), with the drive gear changed to that of the Lucas unit. Pretty simple undertaking. Pretty big and ugly too, and also has "issues" over 4000 rpms as did the cars they came from, unless you modify them with high output modules and coils. Due to increased heat, the H.O. modules and coils don't last as long as the stock units, but probably much longer than points. The standard MGB curve from DUI is 22 degrees crank advance, onset from 1000-3000rpms+/-. I think they use an adjustable vac advance.
Jeff Schlemmer

Anyone who claims to offer a replacement for 'the usual non-functional Lucas item' will only get two fingers from me. As an alternative the MGOC offers a 13-point replacement for mechanical advance for those of us with finctioning Lucas items, but at nearly 400 quid they won't be getting an order from me either.
Paul Hunt 2

The DUI distributor uses a special module and coil to resist higher temps. The bronze bushings used on the shaft are machined to a very close tolerance to reduce timing scatter. The problems reported above 4000 rpms have been virtualy eliminated. It is a big sucker and does require moving the brake switch forward on early cars (not a big job). The unit I installed made the car run very well indeed and improved the performance output from the supercharger. DUI does not offer a vacumm advance at this time. RAY

Thank you to everyone for the information. At $400 I think that the OEM distributor will serve for a while longer. Dave
PS to Clifton - Sorry, we told the Seahawks not to run the score up on the Panthers, but I guess they must have gotten carried away :))
David DuBois

425 Canadian dollars is 208 GBP about the cost of a new 45D and electronic ignition (educated guess mind). Which if your in the market for a new distributor with electronic ignition makes it a competitive option.

I either read on here or the MGOC BBS that a company was going to re manufacture the 25D. Although I could have been dreaming about it because I couldn't find thread when I searched for it again. Did anybody see the thread or was it just in my head?

This thread was discussed between 20/01/2006 and 23/01/2006

MG MGB Technical index

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