HEI Distributor

[claude brousson]

I have my 455 HEI distributor out at the present for a preventative
maintenance check. So am wondering a few things and would like some
input from those you who have had experiences with these.The coach is a
'77 and has 90,000 miles

1.I have never replaced the top coil although carry a spare. Is it
likely to fail with this mileage and age?

2.The pick up coil underneath--is it likely to fail or do they last
forever so to speak? I took out the pole piece and assembly before
reading the book.(unfortunately) The book suggests caution as one could
change the polarity of the assembly. How can I tell if this has happened
and is there much risk that it has happened? What I did was take out the
three small screws and lift out the star wheel and separated it from
the pickup coil.

3.I note that at the point on the shaft where the lower oilite bearing
is there is some wear on the shaft. I would have thought the wear would
have occured on the bearing but it appears to be mainly on the shaft.
The difference in diameter of the shaft from non worn area and worn area
under the bearing is .003 That doesn't seem like enough to be a problem
at the lower gear end of shaft but what do you think? As the wear is on
the shaft mainly ,if one were to do something about it ,would one
purchase a new shaft and are they obtainable?

Thanks in advance for any wisdom from the Net.

Claude in Victoria--where I just have to say it--the temps are still
warmer than Alberta and the bulbs are already up!!

 

[kara m kosier]

A couple of other notes on the HEI distributor. I have trouble with
light bulbs, so I don't delve too deeply into electronics.
According to GM's literature, the pickup coil and the secondary
ignition coil have polarity built in and must be used in matched sets.
Oddly enough, rear drive Oldsmobiles are of the opposite persuasion
from Toronados(and GMCs) Real Caddillacs and Chevrolets are the
same as Toros and GMCs. It has to do with magnetism and which
side of the motor the starter is mounted. Trust me!!!
However, I had a mismatched combination for some long time and
never saw any difference. The benefits of dumb luck.
gary Kosier
- ----- Original Message -----
From:
To:
Sent: Friday, December 31, 1999 5:49 PM
Subject: Re: GMC: HEI Distributor

>

>
> maintenance check. So am wondering a few things and would like some
> input from those you who have had experiences with these. The coach is a
> '77 and has 90,000 miles
>
> 1.I have never replaced the top coil although carry a spare. Is it
> likely to fail with this mileage and age?
>
> 2.The pick up coil underneath--is it likely to fail or do they last
> forever so to speak? I took out the pole piece and assembly before
> reading the book.(unfortunately) The book suggests caution as one could
> change the polarity of the assembly. How can I tell if this has happened
> and is there much risk that it has happened? What I did was take out the
> three small screws and lift out the star wheel and separated it from
> the pickup coil.
>
> 3.I note that at the point on the shaft where the lower oilite bearing
> is there is some wear on the shaft. I would have thought the wear would
> have occurred on the bearing but it appears to be mainly on the shaft.
> The difference in diameter of the shaft from non worn area and worn area
> under the bearing is .003 That doesn't seem like enough to be a problem
> at the lower gear end of shaft but what do you think? As the wear is on
> the shaft mainly ,if one were to do something about it ,would one
> purchase a new shaft and are they obtainable?
>
> Thanks in advance for any wisdom from the Net.
>
> Claude in Victoria--where I just have to say it--the temps are still
> warmer than Alberta and the bulbs are already up!!
> >>
>
> Claude -- using numbers from above,
> 1. Some of these last almost forever. Mine failed on a trip at about
> 105,000 miles and I did not have a replacement with me. It took me a
while
> to find the problem. The test of the primary and secondary circuits as
shown
> in the GMC Maintenance manual said the coil was good, so I replaced the
> module, the cap and rotor and then the pickup coil and still had the
problem.
> it took me a while to figure out that I was having an intermittent
failure
> of the coil. When it got hot it would open the circuit but when testing
it
> the circuit was OK. I would suggest carrying a spare, even if you get one
> from a junkyard Toronado. A new one will cost approximately $50 to $80.
>
> I have had three failures of the electronic module in about 110,000.
>
> 2, I had a pickup coil go bad when my GMC was about 10 years old and
again
> last spring. If you take it apart (and when you put in a new one) the
three
> screws must be loosened and after the shaft is put back into the
distributor,
> the shaft must be slowly rotated by hand and the points on the star wheel
> rotor must be observed and adjusted to make sure that there is an even gap
> all the way around. They don't even come from the parts store as new ones
> adjusted properly. Then the three screws are tightened. I know someone
who
> did not do this adjustment and they got about 30 miles down the road and
the
> wires in the pickup coil burned up due to the heat buildup due to one of
the
> shaft points rubbing on the pickup coil. I doubt that there would be
much
> of a problem with accidentally reversing the polarity if you don't put
power
> to the unit. This is similar to what used to happen to old style
generators
> (before alternators). I'll have to go back and reread the Maintenance
> Manual. If in doubt, I believe there are procedures for re-polarizing it
in
> the manual.
>
> 3. I too noticed some wear on the shaft whereas the bearing looked OK.
On a
> trip to a junkyard I pulled three distributors from 455 engines and check
> their shafts and found one that looked fine in an auto that had 40,000 on
it
> when wrecked. I replaced my shaft with the auto one but used my counter
> weights and springs and it works fine. I would suspect that rebuilders
use
> new bushings and probably either use a new shaft or build it up and turn
it
> to the right dimensions. Note that the springs can loose tension over
time
> and the counter weights can wear where they pivot on the pins. These
things
> can throw your advance off. However, I doubt that .003 of wear would be
much
> of a problem.
>
> I would suggest that you carry a new rotor, cap, coil, electronic module
and
> pickup coil. These don't take a lot of space and if you break down 50
miles
> or so from the nearest small town as I did east of Tombstone, AZ last
spring
> you'll be glad to have them with you. Sometimes trial and error by
> substituting parts is the only way to figure out the problem at the
roadside.
> I also suggest that you carry a small pin punch that fits the pin hole on
> the lower distributor gear or you'll have a hard time getting the gear
off.
> I found a rusty nail in a fence post off the road that fit but have now
added
> the small punch to my traveling GMC tool box.
>
> Emery Stora
> 77 Kingsley
> Santa Fe, NM

 

[claude brousson]

Thanks Mike Linderman, Steve Ferguson, and Emery Stora for your ideas
and input.

Claude