[xj-s] Advance & retard spring

["Lee Opausky" <Opausky@netcom.ca>]

Further to Kirby's in #206, here is some more numerical  info on spring
measurement.
From used Lucas distributor, approx 70 Kkm, ' 88-89, with nylon clip still
in place in the rotor shaft (therefore springs not stretched with star
wheel removal) :
length of HEAVY spring measured between the inside contact points of the
outermost point on each loop in an unstreched condition :18.7 mm ( approx.
same as K's) it has 4 full coils, distance between coils per feeler gauge
.018, .018, .022 "
For the record, the LIGHT spring : 15.9 mm, 6 coils, distance between coils
.010 " in all 5 spaces. 
Given the feeler gauge measurements, one would doubt that the above springs
are stretched to a significative degree.  Yet, this is the distributor
where I reported earlier that the rotor carrier shaft pivot plate come to a
physical stop against one of the spring mounting pins BEFORE the heavy
spring could come into action.( My apologies to suggest earlier that the
plastic thingy was the stopper at high revs, it is indeed the stopper at
idle). In conclusion the heavy spring on this distributor is ineffective,
weather the springs are actuated by rotating the rotor shaft or by moving
the weights.
So, I am sitting here typing, with my distributor on the top of a coffee
can, stripped down to the lower housing, one end of the springs detached
from the mounting pins, the two shafts still held together by the original
nylon clip: pull out the centrif weights - hold the heavy spring against
the empty mounting pin to see how mutch shorter this spring would have to
be to actuate - well, not mutch shorter - maybe the sum total of the feeler
gauge measurements  .018 +.018 + .022 = .058"  would be enough.
Therefore , a distributor like this, working only with the light spring,
will give more advance to the ignition at lower rpm's. Not a problem if you
are doing a 62.5 shift, but in the city we often dont get above 2600 rpm.
Lee Opausky

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