Re: HEI vs. Others.... Some questions
2 things that will make GM more reliable:
The rotors - use white or blue ones. The black ones use
carbon to color it, carbon's a conductor.
Caps - use genuine GM - they have more insulation barriers
A loose or bad plug wire will also help it flash through the
rotor or across the cap.
The modules - use the proper heat sink grease under the
module - lots of it, not just a dab.
There are several types of ignition grease available - some
are made to sell but not to use.
The silicone grease you use on plug wire boots IS NOT THE
RIGHT ONE for under the module!
It has to be HEAT CONDUCTING GREASE, not insulating grease.
The best type is available at electronic stores - or in the
capsule that comes with a new module = or should.
If the tube says you can use it on plug ends and under the module
it will only cause trouble.
When they say "modules" on that tube, they mean on the
connections, not under it to carry heat away.
Wrong grease = overheated module = dead module.
As for ignition types comparison, any bubblehead with an
ignition scope can easily tell the difference between ignition
Most tune-up shops have them - just talk to any tech that
knows how to use one.
He can easily show you 2 things: Open circuit voltage, ie.
30, 40, 45 KV (KiloVolts) etc. And he can show you plug
(The maximun output of a coil is measured with a plug wire
pulled off, otherwise all you can see is the required
voltage to fire that plug - that required voltage is determined
by the plug, mixture, compression etc, not the ignition
system itself. Open circuit allows the coil voltage to go up to it's maximum.
Burn time is measured with the plug connected - it's the
time the spark is sustained across the gap, not the same as
cylinder burn time.)
KV is the maximum voltage it can produce, burn time is how
long the plug actually fires in milliseconds.
Stock points systems: 28-32 KV, 1.5 ms burn time.
Run of the mill electronic ignitions, Pertronics, Jacobs, etc
28-32 KV 1.5 ms
Ford Duraspark (I) 28-32 KV 1.5 ms
Ford Duraspark II, TFI 40-45 KV, 2.5 ms
GM HEI - either type 40-45 KV 2.5 ms
"Gold box" Chrysler 30-35 KV .75 ms
"Run of the mill" electronic systems' biggest advantage
over stock points is they have much less dwell variation,
so there's less timing variation between cylinders.
The older Duraspark (I) modules have better dwell control
as well, but when used with a coil with lower primary
resistance (ie some aftermarket "hot ones" or TFI coils,)
they tend to overheat, possibly burning out.
The Chrysler "gold box" modules have good dwell control,
can be triggered either with points of pick-up coil, and
have a faster rise time.
The Duraspark II and the HEI both have a current limiter in
them, causing the "variable dwell" effect.
That current limiter allows the use of a lower resistance
ignition resistor (or none as in HEI.) That way the coil
can charge faster with more energy without the resistor
MSD uses a different concept than the above Kettering types.
It "hits" the plug several times with a very fast rise time,
virtually "blowing" any fouling or crud off the plug.
It's available voltage is quite high as well.
The burn time is shorter, but there are several of them at
lower speeds, and at higher speeds it reverts to just one
hard hitting spark.
For the money and simplicity, MSD's probably the best
ignition system ever produced.
Combine it with the larger cap from an HEI or Duraspark II
for the better insulation and you have a great combo.
But - Any system when replacing one that's not working correctly
will get the user to say "It works great!" (And I think
almost anything is better than the Prestolite.)
Ask a tune-up guy that isn't trying to sell you parts or a
"kit" about KV and burn times. Have him show you.
Or - you can look up original specs, not manufacturors hype
trying to sell you their elixor or snake oil.
Or - you can even call Sun Electric and ask to talk to an