[TR] Distributor help

Randall TR3driver at ca.rr.com
Wed Apr 8 19:14:40 MDT 2015

> I have a '56 TR3 with a 40798B Lucas distributor installed.  

What are the numbers on the vacuum advance unit?  There should be a 6 or 8 digit part number, like 54413565 and also a set of 3
numbers separated by dashes, like 2-6-3.  (Those are the number for the 40795 distributor, yours will be different but similar.  I'd
like to have them for my database.)

> Can anyone give me an idea of where this 
> distributor is used?

I have it listed in my database for 66-67 TR4A with high compression, but can't find any indication of that in the Lucas catalogs or
Triumph documentation so it is probably a mistake of some sort.  A little poking around with Google turned up applications like
Singer Gazelle and Hillman Hunter.

> It obviously can be used in a TR3, but 
> what is the difference from the ones listed in the parts 
> books? 

The functional difference will be the advance curves (both centrifugal and vacuum).  Compared to a 40480 (which is listed for later
56 TR3), the 40798 gives quite a bit less advance up to roughly 2500 rpm, then lets it go several degrees higher by 5000 rpm.

But of course, since the parts all interchange, it is quite possible that someone has modified the advance curve to almost anything.

Mechanically, it's a model 25D so there are lots of differences with the model DM2 that would be original to your 56 TR3.

> Finally, does anyone know of a place to find a vacuum 
> unit for this distributor?

Any of the 25D advance units will fit and work.  To be on the safe side, stick with one that provides roughly the same advance or

Another alternative may be to have your local independent auto parts store send it out for rebuild.  I did that many years ago and
was very happy with the results.  The result looked and worked like new, and cost less than buying new.  Turnaround was 3 or 4 days
as I recall.

-- Randall  

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