'29 distributor question

[jps]

What is the normal amount of slop on a distributor shaft?  I haven't measured the amount of backlash on the rotor on my 1929, but I am sure there is at least 5-10 degrees, which seems like a lot to me.  I have been fighting inconsistent spark for a long time, and am wondering if a worn gear is the problem. 

[Mark Shaw]

John,

    Backlash should not be an issue since the rotor only travels in one direction.  If the drive gear is worn, you could have inconsistent rotation. 

You can check this by hand cranking the engine with a VOM meter connected to sense when the points fire the #1 spark plug relative to TDC on the flywheel.

 

[Robert Engle]

Rotating the shaft will operate the mechanical advance flyweights.  If the flyweights are stuck in advance, you will easily feel the extra play in the shaft.  You may need to pull the points base plate and see the condition of the mechanical advance.

 

Bob Engle

[Old buicks 2]

I have a set of gears for the 29 Buick.   See attached photo

 

Tom

[raydurr]

More than likely the slack that you are experiencing is play in the advance mechanism. This is totally normal. You can check your timing with a timing light. If the mark stays fairly steady throughout various engine speeds you are ok. If the mark is all over the place then you could have wear in the drive gears, breaker plate, points or the advance mechanism.

[jps]

I am having trouble starting.  The last time I got it running, the timing mark was all over the place and the engine ran rough.  When I put a self-powered timing light on plug #1 while cranking, lately I get 2flashes of the light together instead of just the one, or it may miss a fire.  So the spark is erratic .  I have replaced every electrical part in the system and the problem persists.  I was thinking along the lines of what some of you said regarding the gear and the advance.

[Guest]

It is possible the bushing in the housing is worn out, allowing the shaft to move sideways altering the gap, dwell and timing.

[edinmass]

Have the distributor placed on a Sun Distributor Tester. I will be out of town till Monday, if you want me to check your for you, you can mail it to me in a priority USPS box, with a pre paid return label. I will check it for you no charge. I only need the distributor.......not the cap or rotor. I was planning on making a video with my machine, like I did for coil testing last week. Look for it in the technical area. If you send it, I will use you unit in the video. PM me if you want to participate. Ed

[jps]

Thank you all for the advice and ideas.  I will have to think about what I want to try next.  I do have another distributor and another generator, so I could swap around some gears and check the automatic advance mechanism.  A few weeks ago I took the spare distributor apart, so now I may clean it up and try it.

 

I sent a few PMs

[Oldtech]

I agree with Tinindian. Sideways play in the shaft will cause your problem. It should be the old mechanics ideal ! Free with no play.

[Bill - 29 Buick]

I’ve heard that the grease gets spun out of the dist. gears and you should put a few drops of light oil in occasionally to keep the gears lubricated. 
 

Bill McLaughlin 

1929 McLaughlin Buick