Distributor shaft play

[nmerrill]

I recently put together a 5 window 20V distributor - drilled 5 window 20v shaft for the shorter 20V gear.
I replaced the shims/ washers at the gear, but am concerned I have too much axial / vertical slop in the shaft. Maybe 0.5mm - definitely more play than the New distributor I have.

Anyone have any thoughts on how much play is OK, or if some will definitely be an issue?

[themagellan]

A little back and forth should be OK

Post a video and sorry no one replied to you earlier

[nmerrill]

I'll get a vid up - maybe tonight.
I'm thinking that the drive gear on the cam should force the dizzy shaft in one direction as it drives it, and a little slop shouldn't matter since the cam will always be driving the dizzy gear... Sounds good anyway!

thanks
N

[nmerrill]

Here a video of what I'm talking about.



Not sure this will really move around while running (cam gear "pulls" down on shaft) or that the Hall would care.

Thoughts?

[vt10vt]

The cam will push the shaft up into the housing when the gear engages and you tighten down the distributor clam, that looks perfectly normal. As long as the gear can't move on the shaft at all but I don't see that happening.

[PW200-20VT]

When I performed an overhaul on my distributor assembly I had just as much "play" in the shaft (up and down) when I reinstalled everything.

No problems.

[nmerrill]

Nice, one more little detail done...

Thanks
N

[88a5tq]

I went to the hardware store and bought machine bushing washers I think they were called. I've put probably 10 to 15k miles on it and have since looked it over and found no peculiar wear on the gear. I used a combination of widths to close the void just because but I didn't make it tight. Sounds like either way would be okay

[nmerrill]

Then I read this from an old MG thread:


Author: the_natrix [ Sun Nov 25, 2007 6:17 am ]
Post subject:
crank trigger is not suceptable to what is known as "jitter"

jitter occurs as there is play between the distributor shaft and the distributor housing. And the play between the distributor's gears and the camshaft gears.

this jitter is manifested as the engine is running and vibrations cause the distributor shaft to move slightly advanced, and then slightly retarded, "jittering" around in the free play mentioned before.. this jitter reveals itself as ignition timing bouncing around small amounts, sometimes up to 5 degrees or more.

in an ordinary engine producing nomal power levels this can be acceptable but is generally not wanted.

in a high output engine, especially engines running very close to the detonation limit of their combustion chamber design. This "jitter" if not limiting power output (by retarded timing below the highest jitter advance), could prove to be disastorous.


We don't want no stinkin' Jitter, even in my wimpy "normal powered" engine.
Guess I'll do some shimmin'

[PW200-20VT]

tell me where you buy the thin metal shims that need to be added.

I guess i could tear it out and rip off the new bronze cog...

[nmerrill]

Get in touch with this guy - he's got a good selection...
http://www.glenn-ring.com/bosch/

I've spent a fair amount of time looking for the correct size sims (correct ID) and came up short... particularly the fiber thrust bearings/washers.

He's got 'em.

[PW200-20VT]

Please see the link below.

http://www.audifans.com/pipermail/200q2 ... 22551.html

I am going to order a couple .003" thick shims from your reference but what is the ID for the shims for our 3b distributors.

Please advise and thanks for your help.

[nmerrill]

The shafts are approx. 12.4 mm - at least mine are!

[PW200-20VT]

Can anyone confirm this?

Thanks for the info nmerrill

[nmerrill]

Yep-
The shims he sent were described as 12.5 mm ID, and they fit perfectly.