Ignition distributor general examination topic

[tom_in_nh]

As requested from another post, I would like to start this seperate technical topic, in order to share my experience with the forum. This is a part time hobby of mine, repairing / recurving ignition distributors.

I would like to use a junior Packard distributor as an example. This particular distributor has an external vacuum advance unit that rotates the distributor housing in the engine block. In other words, there is no movable breaker plate inside the distributor housing.

As this distributor belongs to a fellow forum member, I will honor his wish to remain anonymous. Therefore, I will show a general examination of what to look out for, when looking at this type of distributor. There are other tests that are applicable to most distributors - I will not go into too much depth, as this post can really drag on.

First photos shows his distributor next to an adapter that is needed to properly mount it to my Sun distributor tester. Unfortunately, my adapter's inside diameter was just a bit smaller than the distributor's housing. A little lathe work solved that issue, the photos tell a story. More to follow, will continue tomorrow evening. Long day, longer weekend...

[tom_in_nh]

As time and history marches on, one can have small parts lost, misplaced, etc. Two such examples to show you with a distributor from the above post. Packard (and other makes) have an "octane selector", which essentially is the distributor adjustment for engine advance / retard.

This photo shows a screw that caused minor binding issues.

You can see the rubbing on the octane selector scale here.

And here is the fix, added a lock washer to raise the screw away from the scale.

Another area to watch out for is that pesky ground wire. With a distributor that rotates in the engine block, the ground circuit is completed from the distributor's housing to the vacuum advance bracket (which is bolted to the engine block) via a rigid ground wire. Be aware how this wire is routed. A mistake here can cause the distributor to not move freely enough, while the advance unit does its thing. This is the best (lousy) photo of the ground wire routing cable that I have from the above distributor.

Here is the correct routing from a junior Packard distributor with 14K original miles.

Shall I continue on with this post?

Edited February 2, 2016 by tom_in_nh (see edit history)

[jvelde]

Getting an education, so please continue!

[tom_in_nh]

The major headache with original, unaltered distributors is bushing wear. Here is a photo of a distributor with approximately .013" of side play, using moderate hand pressure. Waaay to much wear - this results in poor high speed operation.

Here is a photo of the innards, showing fragments of a worn bushing.

Another area of high wear is the pins and elongated holes in the centrifugal advance weights. Weak springs are an issue, too.

[tom_in_nh]

One gripe I have with today's manufacturing quality control (lack of), is the inaccurate assembly of a set of breaker points. More specifically, the lining up of the point contacts. On some point sets, adjustments are not possible, without major fiddling around. Grab those NOS sets of points when opportunity presents itself!

Spring tension is also very important.

There are also other tests to be made. Condenser tests (series resistance, capacity, leakage), distributor resistance test, cam lobe accuracy, breaker point dwell and variation of, centrifugal advance calibration test, vacuum control diaphragm test, vacuum controlled breaker plate test, etc.

I find that taking care of the small mechanical details results in very satisfactory performance gains. Note that some replacement parts are simply not available as new anymore. Sometimes one has to cannibalize several similar distributors to make one decent working unit. Some machining and fabrication may be needed in extreme cases. It is all about compromise, when unobtanium rears its ugly head.

I hope this topic has been somewhat helpful to my fellow forum members.

Regards to all,

Tom

Edited February 2, 2016 by tom_in_nh (see edit history)

[RansomEli]

Thanks for sharing your knowledge. This information is valuable for the do-it-yourself restorer

[tom_in_nh]

You are welcome RansomEli.

I am currently working on an early Auto Lite distributor that has that pesky clip that retains the breaker cam to distributor shaft.

I'd like to share two photos of a tool that I modified in order to make installation and removal a breeze.

[attachments=787047:IMG_20160226_070341256.jpg]