Ball bearing in distributor?

[Jub]

Does anyone know what the ball bearing inside the distributor does?

I own a 6 cyl. 1971 250 (w114)

[Carpenterman]

It's my understanding that the bearing keeps the breaker plate correctly located as it rotates during advance. Really a nifty little design that provides for the least amount of friction as the plate turns.

[meltedpanda]

that is correct, pretty common in all dizzys I know during the 70's , even on the 8 cyc

[Jub]

Is it vital?....when I first got the car the housing piece (that holds the bearing) was broken and the bearing was loose. I removed the housing piece off another distributer, and replaced it (ball bearing and all). Strange thing is it then screwed it up! So I removed it, and now it runs fine.

What the heck does that ball bearing do (am I missing something)?

[meltedpanda]

been there done that

read this, it is a fussy thing and the right placement and tension is critical. The purpose is explained as well, yours looks a little suspect

when you need vacuum advance is when you will have issues, that is at speed and acceleration

http://www.peachparts.com/shopforum/sl-forum/277286-panda-mess-once-again.html

[Carpenterman]

Yea, you may have replaced the bearing/housing with one from a non-compatible distributor. If it's binding it will mess up your advance. The bearing should at least rest more to the middle of the housing.

The housing could also be bent too tight. I don't think there's an actual tension adjustment for the housing.

[WNC123]

yes, the bearing has a dual purpose. it helps hold down that side of the breaker plate, as well as allowing for smooth movement during vacuum advance / retard. the ball, cap, and the little tab on the breaker plate should all be very clean and lightly lubricated with distributor grease. ideally you should remove the breaker plate, thoroughly clean it, lubricate the friction surface between the plates, then reassemble.
there is a tension adjustment of sorts (at least on the VW distributors i've done). the slot for the securing screw on the cap is elongated to allow for slight up and down movement. which does put tension/pressure on the ball bearing and breaker plate. even though the slot is not overly long, the small amount of movement allowed is noticeable in the amount of resistance the breaker plate has, depending on how the cap is "adjusted" vertically. i set them so that the top edge of the cap is flush with the top of the mounting tab on the breaker plate. that seems to be the way they all are when i disassemble them, or they way they are on nos breaker plates.
it's amazing how well cleaned and lubricated breaker plates work compared to gunked up ones.

here are pics from VW distributors I have rebuilt. as a side note, these distributors are from the 1950's, so the "technology" has been around for a while.

before:


this was during assembly. excess grease was removed before putting the distributor into service.

[Jub]

Thanks everyone! I will replace it (making the housing flush with top surface), ensure that tension is appropriate, and clean the breaker plate. Oh and FYI: that picture I posted actually came from the distributer I took the parts from (mine isn't that mucky). In fact it wasn't until I spotted it in that distributer that I figured out where the bearing in mine came from.

[WNC123]

just when i say that, i get a distributor that has the cap that is not flush with the top of the tab. i tried setting it flush and it locked up the advance plate. i set it to where it was before disassembly and it is nice and smooth. go figure.

[Jub]

Hi WNC123,

I put everything back in flush (but I also ensured that the tesion was not too excessive); it runs fine now. I think the overall issue is to not put too too much pressure on the plates below. Kind of reminds me of the three bears/porrage analogy: not too hot, not too cold, but just right (ie, tension).

FYI: that is one pretty distributer (bolts, wiring, points, plates look flawless).

Thanks again.

[bwostosh]

Been there also, some distributor advance plates can even develop a "wear spot" from the ball bearing which must be filed/sanded/buffed-out to get free float of the moving plate.

[Benz Dr.]

I've been rebuilding distributors for about 20 years and I see this sort of stuff all the time. The ball rolls a bit as the advance plate moves. Too little tension and the plate can lift throwing the dwell angle out. I usually move the small spring so that it's level with the top of the arm that it sits on.
I use Bosch distributor grease to lubricate all of those moving pieces and then I run it on my tester. If the dwell angle changes after appling vacuum, the advance plate is probably worn. Since replacement parts are NLA for the most part, I usually try to repair the plates. They're made from very hard steel to prevent wear but they will if the plates are running dry.
There are a number of ways you can get almost all of the play out of worn distributor parts but sometimes it's best to find better pieces.

Almost impossible to do any adjustments right without a tester.

[donlawson84]

I found this post and was looking over the pictures, what is the bare copper wire going to the vacuum diaphragm? on my distributor, the wire was not connected to nothing, i figured it was a ground / negative and grounded it.

[meltedpanda]

it is a ground for the dizzy

[BioBionicWanderer]

The ball bearing inside the distributor of a 1971 Mercedes-Benz 250 (W114) with a 6-cylinder engine is likely part of the centrifugal advance mechanism. As engine speed increases, centrifugal force acts on weights, moving the distributor shaft. The ball bearing facilitates smooth movement of these weights, reducing friction. This mechanism adjusts ignition timing, optimizing engine performance. If facing issues, it's advisable to consult a qualified mechanic for inspection and potential adjustments to ensure proper operation.