Javelin distributor

[Moises]

About the Lucas 25D4 distributor, Ref. 40795A: Are the two advance adjustment springs the same? Could someone tell me their part numbers and where they can be purchased? Thank you very much.

[David Kemp]

Contact distributor doctor, they have the correct springs.
I bought some for my Bradford.
They need the distributor serial numbers to get the correct parts

[Forumadmin]

Moises. https://distributordoctor.com/ But a word of warning. It is likely there will be wear in the distributor mechanism which far outweighs the advantage of fitting new springs. When racing I used to adjust the springs to obtain the advance curve I wanted. The Distributor Doctor, when he rebuilds a unit, may also do this. He probably also has a selection of spring strengths and lengths as well. If you ask him, he can rebuild to the specification that we worked out together to suit modern petrol.
You can do the same as I did with a timing strobe light (preferably one with a knob to dial in the advance) to check the advance at various engine speeds to get the desired curve. Also check the vacuum advance is giving the correct advance.

[David Kemp]

I agree , you need to check the whole distributor, mine had worn bob weights, bushes & shaft. DD could supply everything barr the shaft. I am running an electronic distributor till I can find a good shaft or build up mine.

[Moises]

This is my distributor. It doesn't have any apparent wear, but I'm not sure if the springs are the correct ones

1780624752449.jpg

[Forumadmin]

The advance curve for that dizzy
40795A 25D4 CCW 1200 10 600 6 350 1 225 1961-74 Morgan, Triumph Morgan Plus 4, Triumph TR4A
recommended alternative to 40ll5 and 40317A for Jowett Javelin
see
https://mgaguru.com/mgtech/ignition/pdf ... _specs.pdf
Just check that it actually is giving that curve. NOTE: the degrees and RPM should be doubled if measuring on the crankshaft. A quick check is to take the vacuum advance off, rev to 2500 crank rpm, see if you have 20 to 22 deg crank degrees of advance. Note many worn dizzies give too much advance at low revs ( note the spec says no advance below 450 crank rpm) so setting the dizzie at low revs (and sometimes static) is pointless ( it will either not start or run badly at low revs). Also worn stops on max advance gives much too much advance and will damage engine (pinging). It is quite common for vacuum advance units to fail or be the wrong ones. This will give you a sluggish engine that hesitates when you put your accelerator down..

lucastuning.pdf