[Tigers] Timing

[Jerry Mo Christopherson]

Some issues on timing:

 

On the mechanical workings:   The old distributors (64) had a system that
did, in fact, wear excessively (you were right, Ron) due to their design.
How many people took the time to take their distributor apart and lube the
wear points????  Ya, me neither!  The newer distributors have a cam system
that reduces the wear ALMOST to nothing.  The weights actually ROCK on the
reluctor arms and don't slide - thereby ALMOST eliminating any wear.  A very
brilliant design!  However, I have seen wear on the weights and reluctor
arms.  Considering the thousands and thousands of times they have "rocked"
against one another, it's not surprising there is some wear after some 40 or
50+ years.  I still lube them when overhauling a distributor.  The cams
design has nothing to do with the "timing curve" of the distributor - only
the mechanical longevity of the system. 

 

The vacuum issue:   When an engine is idling or being used under low power
(i.e. high vacuum), it LOVES more advance.  One way to see this is to change
the vacuum hose from the tuned port (above the throttle plates) and hook it
up to the manifold (full vacuum) below the plates.  You'll then see an
immediate increase in RPM!  This is because the engine is running more
EFFICENTLY.  You haven't changed the throttle position at all, and it runs
faster.  You'll have to turn the idle screw down to get back to your
original idle speed.  I have a graph that shows the advance changes of an
engine.  The ONLY REAL difference in having the vacuum diaphragm hooked up
to either the tuned port or the full vacuum port is at IDLE.  My personal
choice is the full manifold port.  Vacuum advance provides a far better
"drivability" on streets.  My dad's '51 Ford had vacuum advance and that was
long before anyone heard of emissions.  Ford (and other manufactures) spent
a lot of money on the design of their vacuum systems.  I realize the Volvo
didn't have one for whatever reason, but the Alpine 4 Cyl. did - go figure.
The 289 HI PO engine didn't come with a vacuum advance, because it was
designed for racing where there is little time "cruising around on streets."
That is not to say that a vacuum distributor wouldn't work for racing.  I
have no doubt Ford saved money by not having a vacuum distributor.  They
did, however, make a dual point distributor.   The only purpose of dual
points is to give the coil more time to build up its voltage (rise time) at
high RPM.   Electronic triggers don't have that problem.

 

Speaking of ignition:   I just came back from SEMA.  Two companies I enjoy
talking with each time I go are Pertronics and MSD.    With regard to
voltage, the Pertronics rep said all their units - the I, II, and III - can
handle 12 volts to the module.  The only time there was an issue was with a
4 cyl engine.  For some reason (he said he wasn't an engineer and couldn't
explain it), they had to have a resistor after the module and before the
coil.  Their  Ignitor III looks interesting, as it has multi spark and a
revlimiter.  I haven't had any personal experience with it.

 

Concerning spark plugs:   MSD really likes Iridium plugs!  I haven't had any
experience with them; but, if I wanted to change to different plugs, I would
certainly look into them and would ask what heat range to use.  Another
thing they said was that they are backing down on having the larger gap
sizes on plugs (.045+) because at higher engine speeds it's harder to jump
the gap (6AL).  Thus, it's better to go back to the lower gaps like in the
.032 area.

 

Well, so much for my ramblings!

 

Jerry Christopherson

9473187

TAC Insp #58

 

Jerry Christopherson

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