[GMCnet] Distributor o-ring

[Tyler]

I pulled the distributor on the 78 Royale, and it did not have an oring where it sits in the engine. The way I read the parts book, p.7-16 and 7-18,
the old style had an o-ring and the HEI did not. The one I pulled out was VERY stuck/gunked in (I used a steady pull from above with a ratchet strap
on the gantry I built to pull the intake manifold, and then tapped with a rubber mallet for nearly half hour. lots of PB blaster). Should I grease and
re-install with no o-ring?
--
1975 Glenbrook, 1978 Royale rear bath
Raleigh, NC

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[Terry]

If there is a groove for an oring in the distributor and a corresponding sealing surface in the block, I would put an oring in there. Otherwise use
the flat gasket and get the timing right before it gets soaked with oil so it won't leak later. Or use both if you have a problem leak.
--
Terry Kelpien

ASE Master Technician

73 Glacier 260

Smithfield, Va.

[Jerry Burt]

Dick Patterson recommends adding a ground wire from the dist. housing to the eng. block to get a solid ground. There has been discussions on this
forum about this. Do a search for distributor ground.

--
Patti & Jerry Burt
73 Gmc 26' Canyon Lands -
Photos - http://jburt.smugmug.com/GMC-Motorhome
Lots of upgrades but lots to do to make it ours.
Members: FMCA - GMCMI - GMCWS - Pacific Cruisers - 49ers

[Gary Kosier]

Tyler,

All the real Olds distributors had an O-ring originally. I got new ones
from GM a couple of years ago. I would recommend some sort
of antiseize on the aluminum housing where it contacts the iron block. A
little corrosion really sticks those things fast.

Gary Kosier
77PB w/500Cad
Newark, Ohio

--------------------------------------------------
From: "Tyler" <tile...@hotmail.com>
Sent: Friday, March 03, 2017 8:04 AM
To: <gmc...@list.gmcnet.org>
Subject: [GMCnet] Distributor o-ring

[Ken Burton]

Your distributor sticking in place is a common occurrence. The problem in not caused by the absence of a gasket or an O-ring. What you are
experiencing is bi-metal corrosion. (Aluminum distributor inserted into a steel hole.) If you wish, you can get a flat gasket or an O-ring, but that
will not prevent it from happening again. To prevent it I suggest that you lubricate the contact area on the distributor and the intake manifold with
anti-seize prior to reassembling it.

It should be noted that the ground connection for both the 12 volt supply to the distributor and the high voltage return from the spark plugs flows
through this connection. When bi-metal corrosion in that joint occurs, sometimes you will loose the ground path to the distributor components.

So as previously mentioned in another post, an added 18 to 14 gauge wire from the base of the distributor to any bolt on the engine block is highly
recommended. If you have a Dick Paterson rebuilt distributor you will find an unused stud and nut on the bottom of the distributor for this purpose.



--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

[Larry]

Ken Burton wrote on Sat, 04 March 2017 02:08

> It should be noted that the ground connection for both the 12 volt supply to the distributor and the high voltage return from the spark plugs
> flows through this connection. When bi-metal corrosion in that joint occurs, sometimes you will loose the ground path to the distributor
> components.

Ken,
(and the high voltage return from the spark plugs flows through this connection.) Are you sure about this? IIRC, High voltage is on the secondary
side of the coil and not directly connected to the primary side....or have I got this wrong?

--
Larry
78 Royale w/500 Caddy
Menomonie, WI.

[Ken Henderson]

Larry,

Ken H. agrees with Ken B.: The high voltage secondary needs a ground path
just as badly as the primary -- the distributor body serves for both.

Ken H.

On Sat, Mar 4, 2017 at 6:02 PM, Larry <weid...@wwt.net> wrote:

> Ken Burton wrote on Sat, 04 March 2017 02:08
> > It should be noted that the ground connection for both the 12 volt
> supply to the distributor and the high voltage return from the spark plugs
> > flows through this connection. When bi-metal corrosion in that joint
> occurs, sometimes you will loose the ground path to the distributor
> > components.
>
> Ken,
> (and the high voltage return from the spark plugs flows through this
> connection.) Are you sure about this? IIRC, High voltage is on the
> secondary
> side of the coil and not directly connected to the primary side....or have
> I got this wrong?
>
> --
>

[Rob Mueller]

G'day,

Keeping in mind that I am electrically challenged I thought the high voltage
traveled through the spark plug wires to the center of the sparkplug -
across the gap - to the plug body - to the engine block which is the ground.

Regards,
Rob M.
The Pedantic Mechanic
USAussie - Downunder
AUS '75 Avion - The Blue Streak TZE365V100428
USA '75 Avion - Double Trouble TZE365V100426
USA '77 Kingsley - TZE 267V100808

[Terry]

The electric wave of energy starts and ends at ground potential.

--
Terry Kelpien

ASE Master Technician

73 Glacier 260

Smithfield, Va.

[James Hupy]

Hmmmmm? I am surprised you guys don't get into collapsing magnetic fields
and turns ratios and eddy currents and polarity shifts and hall effects and
all that fun "stuff". Just ground that distributor and rule out that as a
problem.
Jim Hupy
Salem, Or
78 GMC ROYALE 403

[Larry]

Ken Henderson wrote on Sat, 04 March 2017 17:45

> Larry,
>
> Ken H. agrees with Ken B.: The high voltage secondary needs a ground path
> just as badly as the primary -- the distributor body serves for both.
>
> Ken H.

Ken,
IIRC, the primary needs ground for the current to flow from ignition switch through the primary windings...then to ground. The secondary is isolated
from the primary by the coating on the many windings. When the primary circuit flow is interupted by points or other electronic means, the magnetic
field collapses, induces high voltage in the secondary and flow is through the coil wire to center of distributor, through the rotor, to contacts in
the distributor, through the plug wire, to the spark plug center electrode.......and THEN to ground at the spark plug. The distributor housing is not
the ground for the secondary. Take a Ohm meter and measure continuity from the secondary lead to the coil case or ground....nothing. Have I had it
wrong all of these years?

--
Larry
78 Royale w/500 Caddy
Menomonie, WI.

[John R. Lebetski]

Both the primary and secondary windings have 2 wires. Primary has 12v and switched ground via points or module. Secondary has one side to ground and
other out to rotor and to ground through plug gap to complete circuit. Next weeks lesson can be waste spark systems like on the Onan.

--
John Lebetski
Woodstock, IL
77 Eleganza II

[Ken Burton]

Larry wrote on Sat, 04 March 2017 17:02

> Ken Burton wrote on Sat, 04 March 2017 02:08
> > It should be noted that the ground connection for both the 12 volt supply to the distributor and the high voltage return from the spark plugs
> > flows through this connection. When bi-metal corrosion in that joint occurs, sometimes you will loose the ground path to the distributor
> > components.
>
> Ken,
> (and the high voltage return from the spark plugs flows through this connection.) Are you sure about this? IIRC, High voltage is on the secondary
> side of the coil and not directly connected to the primary side....or have I got this wrong?

Yes I am. When you fire a spark plug, high voltage and very low current goes through the plug to ground (the engine). The only return path to the
coil for this high voltage and low current is via the engine and the distributor frame on an HEI ignition.

The next time you have an HEI distributor cap off, remove top cover and notice the single (I believe it is black) wire under one of the mounting bolts
for the coil. That is the ground return for the secondary (High voltage) side of the coil. Follow that black wire and see where it goes.

You are correct in your statement that the primary and secondary sides are not directly connected to each other on an HEI system. They do eventually
share a common ground. In a points system the coil primary side ground is interrupted by the points opening and closing. In an HEI system the
ignition module does the same interruption on the primary side. On the secondary side the return to the coil always grounded.

On a points ignition the coil is mounted on the engine so the return is not normally through the distributor frame on most vehicles. Read the below
because this may not be true on a GMC.

I remember very little specifics on GM 12 volt points ignition systems but there is an interesting anomaly on the 73 GMC points wiring diagram. I
really believe it is incorrect. The diagram shows the primary and secondary ground side of the coil wired together. So the secondary ground return
would then be through the points. I do not have a coil here to measure, but if this is really true then the secondary of the coil would also get it's
ground through the points and the distributor frame. I have never seen this before but I guess it could work.

That is probably more information than you wanted to know. Just keep a good ground connection between the base of the distributor and the master
ground (the engine) and everything will work correctly.

--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

[Terry]

"The diagram shows the primary and secondary ground side of the coil wired together. So the secondary ground return would then be through the points"

Electrically they are the same.
That is one of the purposes of the condenser. The other is to absorb the backflow from the primary windings. The third is to reduce/absorb "switch
bounce".

--
Terry Kelpien

ASE Master Technician

73 Glacier 260

Smithfield, Va.

[Terry]

"Take a Ohm meter and measure continuity from the secondary lead to the coil case or ground....nothing. Have I had it wrong all of these years?"

Crank up the voltage on that voltmeter (maybe have to use a megger) and you'll be able to see that resistance of the windings to the ground. The other
end of that spark plug wire circuit has to start somewhere, right? Otherwise there would be lightning INSIDE the coil (and then you will be on the
side of the road).

Can't wait for John's waste spark class!

--
Terry Kelpien

ASE Master Technician

73 Glacier 260

Smithfield, Va.

[Ken Burton]

Bullitthead wrote on Sat, 04 March 2017 23:27

> "The diagram shows the primary and secondary ground side of the coil wired together. So the secondary ground return would then be through the
> points"
>
> Electrically they are the same.
> That is one of the purposes of the condenser. The other is to absorb the backflow from the primary windings. The third is to reduce/absorb "switch
> bounce".

That is not the point. Normally the coil is mounted with the secondary connected direct to ground. In the case of this diagram the secondary is
shown as switched to ground through the points. Also the secondary fires when the points are opened (not closed) so no return path would be available
until the points closed again. I am really questioning whether this will really work as diagrammed. I have never seen one wired this way on any
points type ignition. I really need to meter a GMC coil to see if this diagram is really true. At this point I do not think it is.

Note: The condenser / capacitor is there to reduce the kick back and reducing arcing across the points when the points are opened.

--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana

[Johnny Bridges via Gmclist]

The condenser also makes a tuned circuit with the coil to maximize the spark. The system won't work without it.

--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

[John R. Lebetski]

Ken B I don't have that diagram to view but I bet it is just poorly drawn. One line connected with a dot or not could be easilly omitted or miss
drawn. It's s very simple concept either of us could draw on a bar napkin in 30 seconds. Over the years I have found many errors in GM factory service
manuals not surprizing give the task of so many vehicle platforms and RPO variables not to mention mid year changes.

--
John Lebetski
Woodstock, IL
77 Eleganza II

[Ken Burton]

Thanks John. That is what I'm thinking too. Especially since the diagrams is for the first year that the GMC was sold.

I saw it on the 1973 GMC wiring diagram so I mentioned it in case I was incorrect in my understanding on how it normally works on a GMC.

It is not that important because it has worked correctly for many, many years on many, many vehicles.

Someday I will run into someone with a spare coil and I'll satisfy my curiosity with an ohm meter.

This is an interesting academic exercise.

--
Ken Burton - N9KB
76 Palm Beach
Hebron, Indiana