Another mystery ignition module failure

[jerry work]

Another thing I found new to me were all the running changes to wire harness, ground wire/strap, cap and rotor. My very good local NAPA store and I always used 1976 455 as the target when looking for parts for either our 77 Clasco 455 or our 78 Royale 455 (engine replaced when new with a turbo 455 that was later changed to non-turbo 455). We always used the yellow wire coil to get polarity right, but it sounds like I/we really needed to be more specific in matching all the parts to the actual distributor in the coach. It it is not known original to that specific engine, the distributor could be from any where along the running change line. Year alone is not enough and who knows if those running changes survived the parts consolidation efforts by the OEM part suppliers or aftermarket parts suppliers.

The good news is both coaches performed really well so maybe I am making too much out of all this.

Jerry

Jerry Work
The Dovetail Joint
Fine furniture designed & hand crafted
in the 1907 former Masonic Temple building
in historic Kerby, OR
http://jerrywork.com

>
> I, too, found this very informative. I was especially interested to see the note about the small drill mark on the drive gear. It says if that is not properly aligned then the distributor will be 3 degrees out of phase. Never heard that before. As many times as I had distributors out and put them back on our two coaches it would only be random luck if I got them properly aligned. No mention of how that might effect performance but one would expect that to impact the magnetic field and current in the coil.
>
> When installing the FITECH fuel injection I learned that the wire size changes inside the bundle on the wire going to B+. That transition point is also a place where corrosion could play a role in less than optimum performance.
>
> Jerry
>
> Jerry Work
> The Dovetail Joint
> Fine furniture designed & hand crafted
> in the 1907 former Masonic Temple building
> in historic Kerby, OR
> http://jerrywork.com
> ========
> Message: 13
> Date: Sat, 30 Jun 2018 07:27:59 -0400
> From: Ken Henderson
> To: GMC Mail List
> Subject: Re: [GMCnet] Another mystery ignition module failure
> Message-ID:
>
> Content-Type: text/plain; charset="UTF-8"
>
> JD,
>
> Thanks for that link! That's by far the best HEI description I've ever
> seen. And it even has a reference to the GMC MH!!!
>
> Ken H.
>
>
> On Sat, Jun 30, 2018 at 12:42 AM Jdlisenby <

>
>> The module discussion led me down the internet rabbit hole reading up on
>> the HEI, I haven't worked on one since high school. I found this discussion
>> useful, with a good description of proper coil selection and applications.
>> http://www.pontiacpower.org/HEI.pdf
>> --
> ==========

 

[john r. lebetski]

The ground lug that goes to the coil is often bad as the screw threads into plastic and only hope of connection is the star washer. Been driving GM
HEI vehicles since 1975 and never had a module failure.
--
John Lebetski
Woodstock, IL
77 Eleganza II

 

[BoboBob]

couple different things that I saw in all my years in the business

sometimes when the dist cap get changed the ground strap that goes under the coil
and up to the harness on the cap forgets to get moved from the old cap to the new cap.

most of the time this will give the coil a short life but sometimes the module too.

second one is the alternator which is an AC charging device the has a diode trio
and a rectifier bridge that limit the charging of the alt to one way-dc current.
if one of those two go bad it can allow AC current into the system taking out the
ignition module. The charging circuit can be checked on an ignition scope to see
if this is a problem
--
Bob Broadwell
76 Eleganza II-Rebuilt performance engine, Manny trans, Manny 1-ton front end living in Las Vegas

 

[johnny]

The HEI isn't a bad design at all.... consider how many millions of them were put on the road.. most of which still operate 40 years or so later. The
biggest problems they face are stray voltages from various places, and heat. The modules made in China take shortcuts internally which
makes them more susceptible to these two problems. Buy American (Still probably offshore, but to a higher spec) and use the good heat sink paste and
keep the connections tight.

--johnny

--
76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"I forgive them all, save those who hurt the dogs. They must answer to me in hell" - ol Andy, paraphrased

 

[gmc2000]

> The HEI isn't a bad design at all...

several foreign auto manufacturers used it under GM licensing and I think I read that chrysler did also. all the ones Ive had that were OEM were very
reliable. I had a module go out in my van somewhere around 250,000 miles and thats the only module failure Ive experienced with and OEM set up. it
gave no warning though and just quit on me at a steady 50mph. check eng light came on too IIRC so jumped the diagnostic port and the check engine
light flashed a code that told me exactly what was wrong.

 

[johnny]

Chrysler had their opwn... basically a transistor used as a switch driven by a tone wheel. Worked like a champ. Used two ballast resistors which
were prone to failure mechanically.

--johnny

--
76 26' Eleganza(?) with beaucoup mods and add - ons.
Braselton, Ga.
"I forgive them all, save those who hurt the dogs. They must answer to me in hell" - ol Andy, paraphrased