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-   -   Internal vs. External Coil in GM HEI (https://forums.off-road.com/jeep-short-wheelbase/2287-internal-vs-external-coil-gm-hei.html)

**DONOTDELETE** 11-10-1999 03:09 AM

Internal vs. External Coil in GM HEI
 
I have purchased a distributor from a 78 GM 250. It has the external coil. The distributor however doesn't have the three wires from it that are described in Larry Maggio's description. Is that because of the external coil? Also, what is the best way to clean this distributor and coil?

Dirt is good. Speed is good. Scabs are good. Life is good.

**DONOTDELETE** 11-10-1999 09:27 AM

Re: Internal vs. External Coil in GM HEI
 
If this distributor has an external coil then it isn't the HEI that you were looking for. The HEI will have the coil(brain) on top of the distributor cap and have the wires that were discribed.


**DONOTDELETE** 11-10-1999 10:40 AM

Re: Internal vs. External Coil in GM HEI
 
Don't rush out and buy a different distributor just yet. The one you have will work. I don't know the wiring schematics, but I would bet that Larry M. will read this post and will probably know what you need to do differently. I check in on the Howell users group once in a while and I seem to recall some guys there using the external coil HEI setup.


**DONOTDELETE** 11-10-1999 11:04 AM

Re: Internal vs. External Coil in GM HEI
 
Unfortunately I have seen only 'installed' external-coil HEI and I dont recall the wiring layout.

The problem I'm having is that I was sure the external coil HEI's were used only in 75&76. I think you are fine to use what you have as long as it isnt computer-controlled and being a 1978 HEI I dont think you need to worry about that.

What type of vehicle was it?


For cleaning really dirty HEI's I use a wire brush and brake parts cleaner. You can dismantle these things almost entirely and do a thorough job if needed. Make sure to relube things when done.


Regards,

LarryM
85 CJ7, 350TBI ,T19 4spd
'00 TJ Sport

**DONOTDELETE** 11-10-1999 02:52 PM

Re: Internal vs. External Coil in GM HEI
 
Is it possible it is NOT an HEI distributor? Are there non-HEI distributors from '78 Chevy truck I-sixes?

Dirt is good. Speed is good. Scabs are good. Life is good.

**DONOTDELETE** 11-11-1999 11:44 PM

Re: Internal vs. External Coil in GM HEI
 
Our son picked up two of these External coil HEI's for me.
I did not look at them till this fall . Have all the parts[wires , gear,]
The pick up looks like a HEI so then if you would have a matching
coil would it not be the same as a HEI??????
Could you change it to a coil in the cap type HEI????????-


**DONOTDELETE** 11-12-1999 12:14 AM

Re: Internal vs. External Coil in GM HEI
 
Anything is possible.

Last two post have got me stumped.


LarryM
85 CJ7, 350TBI ,T19 4spd
'00 TJ Sport

**DONOTDELETE** 11-12-1999 04:46 AM

Re: Internal vs. External Coil in GM HEI
 
You can convert between internal and exernal coils, the base is identical[img]/wwwthreads_images/icons/cool.gif[/img]. The tan/red/lighter color wire is power, the brown/black wire is trigger. You can wire it directly to an external coil, I used a 12V model out of an 86 Astro that outputs 50K volts same as the internal coil[img]/wwwthreads_images/icons/smile.gif[/img]. To mount an in-cap coil you need the wiring plug, the center wire (not marked) is a ground wire for the coil. I like the external coil because the cap is so much shorter, with a good coil the perforemance IS the same (I converted when I put on my TBI).


~|_____
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/-[img]/wwwthreads_images/icons/smile.gif[/img]||||[img]/wwwthreads_images/icons/smile.gif[/img]-\
([img]/wwwthreads_images/icons/cool.gif[/img])-o--([img]/wwwthreads_images/icons/cool.gif[/img])

Randy 80 CJ5


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