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Old 04-27-2006, 09:52 PM
TopCatGr58's Avatar
TopCatGr58 TopCatGr58 is offline
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Location: Portsmouth, Va.
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GM HEI IGNITION MODULES FOR 78-80XS11's

MainlyLinux description on what he's done, along with a
WIRING DIAGRAM, and some photos! The Wiring diagram is 900
pixels wide, but didn't want to shrink it and loose the printed
text in it possibly making it illegible, so bear with the side scrolling!
T.C.
Quote:
The modules I used are from 74-88 chev cars or 75-90 chev trucks.
I bought from our supplier at cost but anyone could easily just go to
the wreckers and pocket a couple.Obviously located in the distibutors
of said vehicles,below the rotors.

The Blue Streak or Standard numbers for the ignition modules is LX 301.
Its the old four pin modules.Any parts store should be able to cross the
numbers over to their brand, or even if they just use the years.

The most beautiful thing about this is its cheap,tested,and should last for years.
I did get around the advance problem by going to a bike wreckers and getting
the old style centrifical weights advance system with the vacume advance.
Those parts were about 20 bucks and easy to change over.

I set the timing to 10 degrees BTDC with vacume advance disconnected.
Bike runs fine.Have plenty of pics and even video.
And last...this set up can be adapted to any bike with the waste spark system.
Wouldnt take much to build one for my 650 twin.
Damn factory ignition box be gone...!All the blasted pages of BS
of people trying to hunt down or rebuild these things.....





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  #2  
Old 04-29-2006, 02:01 PM
mainlylinux mainlylinux is offline
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Join Date: Nov 2003
Location: Michigan
Posts: 211
On stock HEI distributors they are included under the cap near the module. Thumpernow probably included them because they were part of the distributors he used to get the parts from.

Now as to their effect, I did some research. Since the capictor is connected between V+ and ground it appears that it might be an electro static discharge shunt; absorbing a high voltage spike send backwards into the module.

I searched google groups and found people saying it could be an RF filter or a shunt; no one was definitive on the subject. I would say that since Thumpernow had access to them and saw how they were wired in the OEM application it was good of him to include them in the XS application. I have run my HEI modules on the test bench at 10,000 rpms firing a coil without the capacitor, and watched the module waveform and didn't see a lot of noise in the wave (my scope is a very old tek that I'm only kind of proficient with though, so I might have missed it).

Here's a question though - when I did my testing I recorded the spark and posted it to this website which some may have seen; what I didn't post however was something else. When I clamped the coil + line to my bench battery the spark was like you see in the picture. when I HELD the coil + to the battery with my finger the spark was MUCH bigger ( it arced almost an inch).

What explains this? Is it capacitance in my body, is it a connection to earth ground?

Dan
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