Hi Listers, Jerry, Brian, Adrian, and Alan, and anyone I might have missed,
This has been so confusing with so many distributor model numbers out there,
as well as part numbers - recorded - and not recorded.
Thanks for your references/parts researching that you all put in.
It looks like the only 'change of distributor' for the TR4-4A 86mm engine was
at TR4 CT17954. From then on and right through the finish of TR4A production
- it remained the same distributor.
15 out of 19 participating TR4 and TR4A owners report their cars have the
Lucas 25D distributor # 40795A and vacuum unit that operates at '2-6-3'.
(Pre CT17954 TR4s had different specs - I believe a DM2 distributor with
5-12-8 vacuum)
The critical Lucas variables (reflected in model ID#s) for the TR4/4A seem to
be; centrifuge springs, vacuum unit, cam advance range, and weights.
Progress on rebuilding my own TR4A spec'd distributor now is;
1) Bought a very-tight 'newer' used distributor - identical looking to a 25D
40795A but differently # stamped. (I can swap out the body or engrave 40795A
on this body to at least document 'reconfigured' springs and vacuum)
2) Cam is correctly stamped '10 degrees' - jives with factory specs and also
reported by original TR4A owner - Alan Crane.
3) Used the weights from my original shattered '63 25D distributor.
4) I bought new weight springs specified just for the 40795 by Moss - not the
'5-spring assortment pack' sold by other vendors.
5) I will install a 2-6-3 vacuum advance unit
6) In the end I will 'SUN test' to ensure I am getting correct factory
'centrifugal' and 'vacuum unit' advance curve
... starting with the correct pieces it should be a lot easier!
Even though I had over 100,000 on the motor I rebuilt in '74 I am sure the
incorrect distributor/vacuum unit I installed a couple years ago helped
finish off my pistons and rings.
Thanks all - for helping me get back to factory specs - if you have any
questions just ask,
Carl Sereda
'63 TR4 since '74 - CT22326L ... 26 years ownership and still learning...
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