DIY Distributor Repair

Tim Hancock · 09-10-2004, 05:43 AM

One of many problems I have had to address after acquiring my "cheap" 1979 SC is that my distributor had some issues.

-Excessive axial and radial play (1/8" axial, 1/16" radial)
-Vacuum advance frozen
-Mechanical advance questionable

Here is what I did:

-Grind off one side of exposed pin on drive gear then punch out.
-Remove all screws from perimeter of distributor body.
-Remove three allen head screws that retain winding assy from
top (these are difficult to see).
-Carefully rock vacuum assy to free it up and then remove
-Pull entire shaft assy out of distributor body.
-Clean everything
-Free up sticking advance weights with penetrating oil
-Free up vacuum advance plate(it is supposed to rotate freely
back and forth about 5 degrees or so).
-Knock out old top bearing (appeared to be sintered metal)
-Replace bearing with oilite bronze bearing (I had to custom
machine one on a lathe to fit). The shoulder thickness on the
needs to be such that there is only a few thousanths of axial
play when assembled (I suppose shims could be used if you
could find some).
-Reassemble

Before

After

konish · 09-10-2004, 05:52 AM

Tim,
Very cool. I cleaned my dist as well as it was starting to howl...and here I was using belt dressing thinking it was a squealing belt. My top bearing was good, so I left it in. As for shimming, I could not find any that would fit the shaft between the drive gear and the shaft housing. Although barbaric I used some morosso chevy 1/2" dist shaft shims to replace the roasted ones from my dist...

R/
Dustin

Paulporsche · 09-10-2004, 06:25 AM

Good job and pix, Tim. What did you do/use for lubrication?

JK-81SC · 09-10-2004, 06:58 AM

Very nice work. Your "before" picture looks like the distributor went through a fire. I used 3 in 1 oil on my dist when I did a rebuild. I was lucky and didn't have to replace bearings on mine, but it was still a gunked-up frozen mess inside.

Thanks for the pictures.

Tim Hancock · 09-10-2004, 07:17 AM

I lightly greased the internal moving parts and used nothing on the oil- light bronze bearing. I am assuming the oil impregnated in the bearing will suffice. Does anyone have any other suggestions? The whole assembly was dry when I took it apart. The upper bearing was totally shot and the shaft thrust surface was wearing away at the base of the distributor body.

I intend to occasionally (once a year or so) spray a light shot of spray grease thru the inspection window to keep this from happening again.

cowtown · 09-10-2004, 08:16 AM

Very nice. I'm about to replace the internal belt on a 993 distributor, and was just wondering where you got a new drive gear retaining pin for yours.

Tim Hancock · 09-10-2004, 08:51 AM

Colin, I have not pinned it yet. I will make a mild steel pin slightly long then peen the ends over to retain it. I have heard of others using roll pins.

cowtown · 09-10-2004, 08:54 AM

Thanks Tim.

jpnovak · 09-10-2004, 08:56 AM

I would also suggest pulling the clips, sliding off the magnetic rotor assembly, then the coil windings. This will get you down to the advance plate. Then remove the E clips and clean/lube the advance weight plates and posts. If they were that rusty and frozen they need the crud cleaned out. Ask me how I know.

Great job on the oillite bearing.

john walker's workshop · 09-10-2004, 10:39 AM

C-2 and others, distributor pin 930 602 922 00

Jdub · 09-10-2004, 11:10 AM

Fun job and very worthwhile. I used a fairly viscous oil to lube the plates and whatnot

Were you able to save the plastic sheathes that sit over the pins on the advance mechanism plate? These protectors often rot away and most folks don't know to replace them.

I used a section of chain link as my replacement pin. Not a stressed member.

For those contemplating this task it is well worth the time since your car depends on a smooth advance curve. Be careful to remove all swarf from drilling that pin so that nothing gets between the pinion gear and shaft. I had a bear of a time getting one tiny piece out so that the pinion would slide off easily.

John

Tim Hancock · 09-10-2004, 12:30 PM

My advance pins were fine although the lighter spring mnt tang was bent so that this little spring did nothing until the last litle bit of travel (the plastic bushing/sleeves where the spring attaches were fine). I decided this was how it came as there is nothing that could have bent it in there. I did not want to mess with the factory advance settings.

After grinding off one peened end of the drive gear pin I was able to drive it out with a punch.