Jeezus

iTrader: (4)

So I have been reading on here about people saying you have to rev the engine to
4000 to set the total advance, because the centrifugal advance ends there. Then I
have read that the 4000rpm is where the vacuum advance doesn't work. Finally,
here I am in the Haynes manual and it says on page 104

Centrifugal Advance
Leading Starts: 0* @ 500RPM
Maximum: 10* at 1500RPM


What is what? Is it fully advanced at 1500 RPM by 10*? I would assume not, but
thought I would ask beforehand.

EDIT:Brainfart. Looked up Paul Yaws site:

Centrifugal, or "Mechanical" Advance
In case you were wondering, centrifugal advance, and mechanical advance are two
different terms for the same mechanism. The centrifugal advance will advance the
timing based on engine rpm. It consists of two weights held in place by springs
which are attached to the distributor shaft. At low rpm, when the shaft is spinning
slowly, the weights are held in place by the springs. As the rpm increases, the
centrifugal force of the spinning weights overcomes the spring tension, and allows
the weights to move outward. These weights are attached to the advance
mechanism in such a manner that as they move outward, the timing of both leading
and trailing will be advanced. This advance will begin at about 1,500 rpm, reacing
maximum or "total" advance of approximately 20 degrees by 4,000 rpm, at which
point no further advance will result from increasing rpm.

Jeezus

iTrader: (4)

So if I am reading this correctly, I can set my timing light's advancement **** to 6*, start car at
idle and line up the indicator pin with the yellow dot, and at full advance I will have 26* (20* at
full centrifugal advance, plus the 6* at idle)? I am running no vacuum advance.

Jeff20B

iTrader: (13)

That's 10° at the distributor which translates to 20° at the eccentric shaft because dizzy spins at half speed.

I don't use a timing light with a dial. Too boinghorrorific for me.

At an idle of 1k or less, with **** at zero (I assume), L mark should be aligned under pin poking out of front cover. As you rev to 4k, the mark will move a full 20°.

Or if your dizzy has more than 10° of centrifugal advance due to a different curve (the GSL-SE I believe is like this as its curve is different and slightly longer), you will experience more advance down at the pulley; something closer to around 25° of total advance at 4k. Maybe. I don't have one in front of me to test right now. But it makes sense that it would have more advance just looking down into the dizzy at the actual curved slot (12A is straight and shorter).

As for the LT split, I like 10° for a 13B. Use whatever you think it best on a 12A. Yaw recommends 8° or whatever.

I don't use vacuum advance, although maybe I should. Just never got around to messing with it.

Jeezus

iTrader: (4)

I have a 80 dizzy, so electronic with no ignitors.
No trailing.

So rev it to 4k, set timing light at 25* and when the yellow dot is under the indicating pin, it
would be correct?

arghx

iTrader: (3)

Distributor turns at half the speed of the eshaft.

j9fd3s

iTrader: (3)

the advance curves are in the FSM's, they do vary a bit. you should burn your haynes manual, its hazardous waste. foxed.ca

the better way to do it, is mark the main pulley @25 (or whatever) and then you can just rev it up and make sure its right.

i would NOT trust the dial on the timing light

Jeezus

iTrader: (4)

Well, I have it down to 25* at full advance. I might bump it to 28 or 30 later on, but I have to
make a new throttle cable bracket since mine is binding it up.