Distributor Bushing Failure

[Randy Van Winkle]

I have been working with a GMC owner who has a Howell/EBL efi system installed. He emailed me that his distributor, a computer controlled distributor
from a Olds 307 obtained from a junkyard, failed. After further study, there was debris inside the distributor that turned out to be shredding from a
bushing. He put a spare distributor on and within 100 miles it had the same failure. The other change that was made just prior to these failures was
that the oil pump was replaced. Wonder if anyone has heard of a replaced oil pump causing this kind of distributor failure? The Olds distributors have
built-in end play - I'm wondering if the oil pump could have a longer drive shaft that is forcing the distributor shaft up eliminating the end play
upon initial installation then during running is putting thrust pressure onto the edge of the bushings causing it to shred?
--
Randy & Margie
'77 Eleganza II '403'
Battlefield, MO

 

[emerystora]

I have already spoken to Bob about this a couple of times..

First of all one should check to see if the shaft above the bottom gear has a thrust washer (usually with two tangs) and a spacer washer above the gear.
Dick Paterson says NOT to use a thrust washer (with tangs) and NOT to use any spacer washers on an Olds distributor. If you have them take them off.

Also I have found that where people are using a 307 distributor from the junkyard they should remove the gear from the bottom and pull the shaft out of the distributor. When I got my junkyard distributor I had to hammer the shaft out.
They will probably find that the shaft is coated with a shellac like deposit that must be completely cleaned off. This is typically caused by oil setting for years in the junker.
The distributor will turn by hand but when it is spun at road rpms the shaft heats up.

I don ’t think there is any difference in shaft length on the distributor or the oil pump.

If you clean the distributor shaft and properly lubricate it before assembly you should eliminate the problem.

Emery Stora
77 Kingsley
Frederick, CO

>
> I have been working with a GMC owner who has a Howell/EBL efi system installed. He emailed me that his distributor, a computer controlled distributor
> from a Olds 307 obtained from a junkyard, failed. After further study, there was debris inside the distributor that turned out to be shredding from a
> bushing. He put a spare distributor on and within 100 miles it had the same failure. The other change that was made just prior to these failures was
> that the oil pump was replaced. Wonder if anyone has heard of a replaced oil pump causing this kind of distributor failure? The Olds distributors have
> built-in end play - I'm wondering if the oil pump could have a longer drive shaft that is forcing the distributor shaft up eliminating the end play
> upon initial installation then during running is putting thrust pressure onto the edge of the bushings causing it to shred?
> --
> Randy & Margie
> '77 Eleganza II '403'
> Battlefield, MO
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org

 

[wally anderson]

> I have been working with a GMC owner who has a Howell/EBL efi system installed. He emailed me that his distributor, a computer controlled
> distributor from a Olds 307 obtained from a junkyard, failed. After further study, there was debris inside the distributor that turned out to be
> shredding from a bushing. He put a spare distributor on and within 100 miles it had the same failure. The other change that was made just prior to
> these failures was that the oil pump was replaced. Wonder if anyone has heard of a replaced oil pump causing this kind of distributor failure? The
> Olds distributors have built-in end play - I'm wondering if the oil pump could have a longer drive shaft that is forcing the distributor shaft up
> eliminating the end play upon initial installation then during running is putting thrust pressure onto the edge of the bushings causing it to shred?

Could it be an oil issue something like the orifice in the cam galley being plugged? I think you can feel end play from the top with the distributor
installed if is OK.
--
Wally Anderson
Omaha NE
75 Glenbrook
Megasquirt III injection
Bob Stone hydroBOOOOST
Manny reaction arm system
Branscombe Kelsey Hayes park brake
http://wallyandsue.blogspot.com/

 

[Jim Hupy]

Look to see if whoever rebuilt that engine installed an oil gallery plug
that had a .040" hole drilled in it. You can test this by driving the oil
pump with a drill motor in a counter clockwise direction when viewed from
the top. You should see a steady stream of oil spraying on the distributor
shaft. If you do not see that stream of oil, the engine MUST come out, the
expansion plug behind the flex plate must be pulled, the cam gallery plug
pulled and the correct one installed in it's place. No short cuts here. One
the engine builders of GMC engines know, and ordinary builders might not
know.
Once you make that bonehead mistake, you won't make that one again.
"Ask me how I learned that one, over adult beverages sometime."
Jim Hupy
Salem, Oregon

On Mon, Jun 24, 2019, 4:32 PM Emery Stora via Gmclist <

> I have already spoken to Bob about this a couple of times..
>
> First of all one should check to see if the shaft above the bottom gear
> has a thrust washer (usually with two tangs) and a spacer washer above the
> gear.
> Dick Paterson says NOT to use a thrust washer (with tangs) and NOT to use
> any spacer washers on an Olds distributor. If you have them take them off.
>
> Also I have found that where people are using a 307 distributor from the
> junkyard they should remove the gear from the bottom and pull the shaft out
> of the distributor. When I got my junkyard distributor I had to hammer the
> shaft out.
> They will probably find that the shaft is coated with a shellac like
> deposit that must be completely cleaned off. This is typically caused by
> oil setting for years in the junker.
> The distributor will turn by hand but when it is spun at road rpms the
> shaft heats up.
>
> I don ’t think there is any difference in shaft length on the distributor
> or the oil pump.
>
> If you clean the distributor shaft and properly lubricate it before
> assembly you should eliminate the problem.
>
> Emery Stora
> 77 Kingsley
> Frederick, CO
>
> > On Jun 24, 2019, at 3:43 PM, Randy Van Winkle via Gmclist <

> >
> > I have been working with a GMC owner who has a Howell/EBL efi system
> installed. He emailed me that his distributor, a computer controlled
> distributor
> > from a Olds 307 obtained from a junkyard, failed. After further study,
> there was debris inside the distributor that turned out to be shredding
> from a
> > bushing. He put a spare distributor on and within 100 miles it had the
> same failure. The other change that was made just prior to these failures
> was
> > that the oil pump was replaced. Wonder if anyone has heard of a replaced
> oil pump causing this kind of distributor failure? The Olds distributors
> have
> > built-in end play - I'm wondering if the oil pump could have a longer
> drive shaft that is forcing the distributor shaft up eliminating the end
> play
> > upon initial installation then during running is putting thrust pressure
> onto the edge of the bushings causing it to shred?
> > --
> > Randy & Margie
> > '77 Eleganza II '403'
> > Battlefield, MO
> >
> > _______________________________________________
> > GMCnet mailing list
> > Unsubscribe or Change List Options:
> > http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>
>
> _______________________________________________
> GMCnet mailing list
> Unsubscribe or Change List Options:
> http://list.gmcnet.org/mailman/listinfo/gmclist_list.gmcnet.org
>