Some basic timing questions

[Marteney, Steven J.]

Okay, I have read in some GM stuff for my cam (ZZ3, 208/221 at 050,
.474"/.510", 112LSA) that the timing should be 10deg base, 32deg total.
(This may have actually been for a crate motor with aluminum heads, but
that's beside the point.)  What does that mean?  If I had a vacuum advance
distributor I would disconnect the vacuum advance and set the timing at
10deg, right?  Is this analagous to unplugging the EST line and setting base
timing?  Then the 32deg total advance, when does that typically occur, at
WOT or at idle or in between or...?

Here's what I'm thinking, and it's probably wrong, I don't know.  I believe
maximum spark advance is needed when the vacuum is at a max.  By that I mean
low manifold pressure, the throttle blades are closed.  This is because
cylinder pressure BEFORE COMBUSTION is low (because hardly any air is
getting in.)  Conversely, a minimum amount of spark advance is needed when
maximum air is brought into the engine because cylinder pressure before
combustion is increased???  This is peak torque, right???  (This is why less
timing is needed with higher compression ratios because the cylinder
pressure is increased by less volume available than before.)  Am I on the
right track?

Now, assuming VERY SIMPLY I know the torque curve of my perfect motor
(simulations are always perfect right?  ha ha).  Now that torque curve
tracks the BMEP (brake mean effective pressure) of the system (but this is
after combustion right?) and should track the amount of air inside a
cylinder, right or wrong?  So at peak engine torque you should have minimum
spark advance???  I guess that's my ultimate question.  Please refute if
necessary.  Any and all of the above is NOT meant to be an explanation but a
big question.

Additionally, GMECM-related, how does a typical motor traverse the Main
Spark Advance vs. load vs. rpm at WOT, IN ONE GEAR (for starters)???  Does
it tend to stay in one load/air flow column and (obviously) traverse upward
in rpm?  It would seem, in VERY simple terms, if gears are factored in,
again at WOT,  you may be in the 175gps column in first gear, then at say
190gps in 2nd gear, and then ultimately at 208gps in 3rd.  Sound about right
or am I just not getting it?  (I do realize every motor is different,
nothing's perfect in the real world, etc...)

Thanks for the help,
Confused About Timing in Florida (aka Steve)
 
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