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post #1 of (permalink) Old 11-27-2002, 02:21 PM
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HEI vs. Others.... Some questions

Hey all,

I currently have a SB 305 in my CJ. Came out of a Firebird that I bought really cheap. The motor was built for the street, big cam, etc. It came with a Mallory ignition system. The dist, coil, etc was brand new.

I am hoping to drop in a 350 with in the next year after I do a tub swap this winter.

I havea HEI dist. from a 1985 Suburbon that I parted out last year.

First, I'd like to say that the Mallory has worked fine for the most part but if the battery gets low it causes problems. Im refering to when I'm winching, etc. I have been told that the mallory needs a lot of juice.

Will the HEI be any better?

In order for me to fit the HEI I am gonna have to modify the firewall for it to fit. Is it worth doing this?

So my question is why should I go with HEI?

(as normal just sitting here at work thinking of my jeep)
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post #2 of (permalink) Old 11-27-2002, 04:11 PM
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Re: HEI vs. Others.... Some questions

HEIs in my experience have a very bad habit of having modules go bad at the worst possible time. I've never owned a GM with HEI that didn't have at least one module go bad, no warning. Several years ago I collected the parts to do an HEI conversion to the CJ, haven't done it because my experiences with them keep reminding me not to trust it. [img]images/graemlins/grin.gif[/img] Not sure why I got the parts together in the first place. [img]images/graemlins/tongue.gif[/img]
post #3 of (permalink) Old 11-27-2002, 09:53 PM
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Re: HEI vs. Others.... Some questions

Gee-wiz,Golly gosh.
I've had many GM H.E.I vehicles through 20 yrs of driving
and never had a problem with them.Lots of other people I
know have too.And I live in Wisconsin with road salt in the
winter,moisture,and no garage (a bitch in the for winter for
older do it yourselfers like me) and consider the conditions
that my vehicles and others have been in to be harsh.What
gives,do you think?

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post #4 of (permalink) Old 11-28-2002, 04:09 AM
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Re: HEI vs. Others.... Some questions

[img]images/graemlins/tongue.gif[/img] You have a LOT of different ways to go without a firewall chop job. You can use the low profile after-market distributor available from SUMMIT with a remote coil. By going that way you can go with an MSD setup as well. The GM HEI IS a pretty reliable setup, no question about it. They do quit now and then from rotor failure or a module, but generally they are OK. The truth, however, is that in the lab they are not as good as the MSD setup or the remote coil Ford style. TR proved this in his ignition lab. [img]images/graemlins/tongue.gif[/img]
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post #5 of (permalink) Old 11-28-2002, 11:59 AM
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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
burn time.

(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
impeding it.

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
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post #6 of (permalink) Old 11-28-2002, 04:39 PM
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Re: HEI vs. Others.... Some questions

[img]images/graemlins/tongue.gif[/img] Er.....ah...what he said....I think you got your answer. [img]images/graemlins/crazy.gif[/img]
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