is this a distributor axial-play problem?

[vairter]

I was trying to diagnose a small issue with a dwell setting (it was reading 57 degrees instead of the 59-65 degree spec) and I pulled the rotor off to see if the points rubbing block was on the apex of the shaft.  As I was rotating the shaft, the shaft would elevate itself by ~ 5mm (yes, millimeters)  as I would rotate it by 20-30 degrees, due to helical gear meshing I assume.

 

I've read many warnings about excessive axial play in these distributors, which I assume one would diagnose with the distributor off the engine.  Unfortunately, I didn't really take a close look at this while the distributor off the engine.  Now it's installed, with timing properly set, and I wasn't inclined to remove it again.  

 

Should I be concerned with this much axial movement of the shaft with the distributor installed and helical gears engaged?  This does seem like a huge amount of axial movement with respect to the outer body of the distributor, which is held fixed...

[Hans]

What's the lateral play like? I think that has more bearing on dwell. I can't comment on vertical, 5mm seems like a lot inside the cap.

['76mintgrün'02]

Axial play refers to up and down play.  It sounds like you are talking about rotational play. 

 

The rotation you are feeling is the mechanical advance feature, which rotates the center post relative to the shaft.  There are two lobes on the bottom of that post and two weights that push on them as they spin out against a pair of springs.  The play you are feeling is normal.

 

Axial play can really only be checked with the distributor removed, because there is also play built into that center post.  So lifting up on the post is misleading.

 

If you were to take a sharpie and make a mark at the base of the distributor, where it meets the housing, you could pull it out and inspect the axial play with some feeler gauges and then just put it back so the mark lines up.  You just need to make sure the rotor is pointing to the same spot on the body.

 

I swapped distributors again today and used the tape/sharpie method.  I just put a piece of tape above the distributor and marked where the clips are on the body and which way the rotor is pointing.  Then use that to install the new one; or reinstall the same one, as the case may be.  I suppose you could get the body out by 180 degrees this way, but it is obvious with a vacuum advance distributor.  You can mark which tab has the notch in the body, if that helps.

 

I took this photo today too.  It shows the weights and lobes I was talking about.  Although this is a weight from a Bosch 009 VW distributor and the little springs have been removed.

 

Tom

[vairter]

Tom-

 

The play I'm describing, with the distributor installed, is a coupled rotational and axial play.  If I pull up on the shaft, it will come up 4-5 mm and also will rotate a bit.  Conversely, if I try to rotate the shaft, it will pop up 4-5mm.

 

It is this coupled motion that I am questioning.  If it were only the rotational freedom, I might not be concerned.  But the fact that the shaft seems to pop up 5 mm when I rotate is what is bothering me.  Does the centrifugal advance on this Bosch distributor just naturally pop up the shaft (and rotor) a bit?

 

Terry

['76mintgrün'02]

No.  Not usually.  There are two basic distributor designs used on our cars, which I just call early and late.  The early style body has a sharp edge on the bottom and the later ones are rounded over.  Based on your description, I am guessing you're describing an early style distributor.  What year is your car and what is the model number on the distributor?

 

In both styles, there is a little round wire clip inside the center post that grabs the end of the shaft.  If that clip is missing, you will be able to lift the center post.  It will only come up as far as the underside of the points plate though, which is about the distance you are describing.

 

I made two little tools for dealing with that clip.  One to remove it and the other to put it back on.  The one that puts it on is just a cylinder that fits inside the bore and around the shaft and when you tap on it, it will push the clip into position.  The removal tool is basically just a pin the same size as the top of the shaft with a step above it that just fits inside the bore.  To use that one, I just clamp the post in a padded vise and tap the tool, which leaves the clip on the tool and the post free to come off... like yours is now, from the sound of it.  

 

There is supposed to be a felt plug stuck in the top of the post.  If you are lucky, the little clip will be in there under the felt.  If not, you will need a new clip.  Assuming I am guessing right.  This photo sort of shows the clip.  Okay, your turn to share some photos.   

 

[tzei]

A 5 mm sounds a bit too much for axial play. Has the rotor kissed the cap? If upper part c-clip is in place check that you have all the washers stacked on the axle between gear and body. How is your lateral play? Upper bushing goes first so maybe it’s time to change that too.

[vairter]

Tom-

 

Distributor number is 0231170164, JFU 4.

 

I removed the distributor to check out play on the bench.  There is about 0.100" of play (my 5mm estimate earlier was a bit high), illustrated by these 2 pics as I push and pull the shaft to its limits.  A final pic is looking down the shaft at the felt pad.

 

I'm thinking there must be something seriously wrong inside the distributor if there is this much free play...

 

['76mintgrün'02]

0231170164 is from a '76 49 state car.  Thanks for the photos.

 

Your estimate of the play was a little high due to the added play built into the center post.

 

The play you see is largely from missing fiber washers on the shaft.  There should be one between the gear and body and another inside.  Each of them are around .035" thick, more or less.  The rest of the play is taken up by shim washers, to reduce it to just a couple of thousandths.  That play will make for inaccurate timing due to the gear rotation that you noticed. 

 

That distributor needs a tune-up. 

 

The other thing you'll probably find is that it is giving somewhere around 36-38 degrees of advance, which means setting timing for all-in advance will not leave a lot at idle.  Hard telling though, just guessing.  I have five of that model here and they seem to wear pretty consistently.

 

Here's another current post, where Moto Carlo fixed his by replacing the fiber washer inside.  (you need two, and possibly a shim washer or two as well).

 

Tom