Jim,
All our 6-cylinder distributors turn clockwise. Turning the "action
plate" or points plate (or the whole distributor) CCW advances the spark.
You
didn't mention the year of your TR6, but I'm guessing you have a Lucas 22D6
distributor with either 41306 or 41306B stamped on it. If so, your vacuum
advance module should have 4/7/8 stamped on it under the crud, meaning
advance begins at 4" of mercury, max advance at 7", and 8 degrees max
advance at the crankshaft. Your retard unit was a 3/10/8, I'd guess.
The best way to tell if your vacuum advance is working correctly is
to
disconnect it and check for changes. Max rpm advance should not change,
since
at WOT (wide open throttle) vacuum advance would be near zero. Vacuum
advance
is for part-throttle economy, not full-throttle power. Also, check the
advance at mid
RPM with the throttle being "blipped". If the advance mark jumps around a
lot even
though RPM only changed a little, your vacuum advance probably works. Try
this
test with the vacuum advance connected and disconnected and compare.
RE"When revving the engine and watching with the timing light I see
"some" advancement, but not a lot. I usually set it around 10 BTDC
(remember my
retard is disconnected) and when revving it advances out to about 20, but
no
further."
The TR250/early TR6 distributors should offer a maximum of 26
degrees of
mechanical advance at "max rpm" (which varies by distributor model). Under
the points
plate, you'll see that one of the centrifugal advance weights has a number
stamped on
it which limits the amount that the mechanical advance can rotate the upper
distributor
shaft. On our cars, it should read "13", meaning 13 degrees distributor
advance, which
equates to 26 degrees at the crank. (The crank of course turns twice as
fast as the
dizzy). On many of our distributors, max advance is further limited by the
springs on the
advance weights. For example, a Lucas 41306, fitted to most early TR6's, is
supposed
to supply 18 to 22 degrees of mechanical advance at 5000 engine RPM (2500
distributor
RPM). Therefore, if you disconnect your vacuum advance, and your engine is
set to 10
BTDC, you should see 28 to 32 BTDC at 5000 RPM if your mechanical advance
is OK.
RE:"My retard has been disconnected, its capped off at the carbs,
but not the
dizzy, do you think I should seal that opening?"
If you do that, your ignition timing will vary slightly with
altitude changes,
underhood temperature changes, and barometric pressure. I suggest you leave
it open.
RE:" Mine sits fully advanced and the
spring is quite loose, no tension at all. I have a funny feeling that its
not right and would like to compare notes."
The early distributors are set up so you can fine-tune the timing
without
rotating the distributor. You push the two vacuum modules together, then
rotate the
retard module in 180 degree increments in the direction of the "A" arrow to
advance,
and the "R" arrow to retard. Try it. I think yours has been overtightened
to the point
where the fine-tuning adjustment is in the fully advanced position, and
operating
the vacuum advance merely stretches the spring without turning the points
plate.
1. Push the two modules together, and turn the retard module in the
"R"
direction for about 5 full turns. When you release it, make sure it springs
back
out into its detent and cannot turn by itself.
2. Loosen the distributor clamp and set idle timing to 10 BTDC with
a
strobe. If the points plate and vacuum module are OK, you'll now have
vacuum
advance, though this won't fix your minor mechanical advance problem.
let me know how it goes,
Tom Marincic
CD3574L
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