The subject of which distributor is appropriate for a TR4 (or 3, 2, or
4A) has come up sporadically. Beyond that has been discussions of part
numbers and questions about how much advance the centrifugal and vacuum
units provide. I hope that the following information will be of some
use in clarifying the issue and identifying mystery distributors. The
source is a series of ?Service Data? publications from the English
weekly ?Motor Trader.? These were issued as supplements to the magazine
and provided a wide range of servicing date (clever name, eh) and
specifications. Here is what is written on the TR2, TR3, TR4 and TR4A.
TR2, 1952-55 Models (Publication date unknown)
Distributor:
Type and service No. DM 2 P4 40403
Advance range (crank deg.)
centrif. 26-30 degrees
vacuum 12-16 degrees
Advance starts (crank r.p.m.) 200-400
Max. Advance (crank r.p.m.) 4300
Cam angle 60 degrees +/- 3 degrees
Contact spring tension 18-24 oz
Contact set No. 420196
Contact breaker gap .014-.016in.
Condensor:
capacity .2 mf
min. insulation 3 megohms
TR3, 1957 model (Published 31 July 1957)
Distributor:
Model No. DM2 Part No. 40480
Contact Breaker Spring tension: 18-24 oz.
Contact breaker setting: 0.014-0.016in
Contact closed period: 60 degrees +/- 3 degrees
Contact set No.: 423153
Condenser capacity: 0.18-.25 microfarad
Minimum insulation: 3 megohms
Rotation (drive end): Clockwise
Centrifugal advance (crank degrees) commences at:200 r.p.m.
Max. centrifugal advance (crank degrees) at: 26-30 degrees
Centrifugal advance springs: 421227
Vacuum advance (crank degrees) commences at 2in of Mercury
Max. vacuum advance (crank degrees) of 12-15 degrees with 18in of
Mercury
TR4 (Published 27 June 1962)
Distributor:
Model No. DM2 Part No. 40735
Max. centrifugal advance (crank degrees) 18-22 degrees at 2,400 r.p.m.
No advance below 450 r.p.m.
Centrifugal advance springs: Part No. 54411614
Max. vacuum advance (crank degrees) 4-8 degrees with 15in Hg.
No advance below 1in Hg.
TR4A (Published 3 November 1965)
Distributor:
Model No. 25D4 Part No. 40795 (H.C. engine)
Max. centrifugal advance (crank degrees) 18-22 degrees at 2,400 r.p.m.
No advance below 450 r.p.m.
Centrifugal advance springs: Part No. 54411614
Max. vacuum advance (crank degrees) 4-8 degrees with 15in Hg.
No advance below 1in Hg.
You will note that the data is not categorized in the same manner for
all models. Nevertheless, it should be clear which distributor was
specified for the modes noted, on the dates in question. It is also
possible that some of the changes in specification may have been made
on a running basis. For example, it is certainly possible that the 25D4
distributor may have been specified later in the TR4 production, yet
before the TR4A. And because the specifications were the same between
TR4 and TR4A, either of the two models in question should function
appropriately.
I hope that this information adds to the discussion. I?d be pleased to
hear of any additional references.
Bob Sharp
Michigan
64-ish TR4
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