Bosch Distributor Mechanical Advance Limiting Screws

[Deilke53]

We don't use abrasive so its really only good for foams, wood and plastics..cuts that kind of stuff in the 200-400ipm range.  very often I cut 0.25" ABS and HDPE or closed-cell foams up to around 4" thick.  Stream diameter is 0.007" so it can do some tiny details.

Perfect for lexan windows, door cards and that sort of thing.  It can cut up to 0.060" aluminum with a few painfully slow passes so I only do it if it really needs to be really accurate and can't easily be cut any other way.

.

2 machines, 5' x 12' work area, one of them is 5axis. Very handy tools.

 

I've used the G10 and FR-4 that you'll see for sale alongside phenolic material and I think will work great for that application too if that's all you find in the correct thickness.  Different resin and different fiber but same idea and similar properties.

 

Let me know if you want something cut.

['76mintgrün'02]

Thank you for the kind offer, Michael.  I hope I can one day take you up on it.  200-400 ipm is amazing speed.  .007" cut width is mind boggling accuracy.  I found two different styles of pads in the ones I just took apart.  I think the larger one could just get trimmed to the smaller size, but I did not scrutinize them that way.  I did trace them both onto paper, when I was taking notes on spring specifications and such.  

 

I reassembled the five distributors I recently cleaned, including points and clips and things.  It is easy to get parts mixed into the stash and helpful to keep original bits together.  There are right hand and left hand points and condensers and I am happy to have examples of both here.  I'm sure there are charts that tell which bits go in each distributor, but I am a little lazy about looking all that up.  I do see why it is important though.

 

The 151 008 distributor had a jumpy timing mark on the Sun, when I ran it the first time (as well as after cleaning).  The center post was a little bit hard to remove from the shaft and it had rusty dust inside.  I cleaned all that off and noticed just how wiggly it was, due to wear.  The shaft appears to be okay, but the inside of the bore is buggered.  I got to use the little gauges I found at the Habitat store recently and that made my day.  

When I slid it inside and tightened it against the bore, I could feel loose/tight/loose areas inside.  Those correspond to the steps in the shaft;

As you can see in the background, some shafts were solid, not stepped.  That is from the 129 033 cast iron one.

 

When I took the 115 045 vacuum advance cast iron one apart, I was surprised to learn that the shaft does not have the keeper clip at the top! 

It uses little shim washers and a larger phenolic washer on top of the center post and all that is trapped under the points plates.  Now I know what the big washers in the rebuild kit are for  

 

Those are the three center post styles I have come across, but there is a little variation in how they cut the steps.

 

I'd like to make the 151 008 work well again, so I looked at using a center post from the other 008, vacuum retard distributor, since it still has a clean bore.  It is not that simple though because the shape of the spring lobes are different

and the size of the advance-stop hole is different too

 

The lobes that the points rub on are in very good shape on that distributor, so it is a shame that the bore's shot.  That is why we need to put a drip or two of oil in under the felt plug once in a while.

 

Back in the day, you could probably contact Bosch and give them the center post's part number and they would send you a new one.  Now, the challenge is how to make the old parts work again.  You can see the worn spot where the pin hits the edge of the hole, limiting the advance (sorry it is blurry)

You can also see the wear on the pins themselves, from the long one hitting that hole, as well as wear on the other side from being pushed by the weights.

Then there is the wear on the weights themselves

 

The springs in these early ones rub on the lobes and cut into them, as the sides of the springs wear a flat spot on that side as well.

 

Part of me wants to weld them back up and grind them back down.  Another part says, as long as they still work smoothly and start and stop where you want them, let the pins and weights be worn.  Just smooth off any weird ridges.  As mentioned earlier, welding will not leave them as hard as they are now.  Maybe hard enough though, if I choose the right filler rod.  The TIG torch has .040" tungsten, so detailed welding is possible.  It is common to weld up the side of the advance hole, to shorten the curve, I am just wondering about doing the other wear points as well.

 

Edited April 28 by '76mintgrün'02
129 033 not 123 033

['76mintgrün'02]

As well, as well, as well.

 

I did attempt to make a little tool to shave the weld off of a welded up pin.  I drilled a pin sized hole in a rod and cut a slot in it, to mount a single carbide tooth that I stole from an old saw blade.  I thought I could just heat it up and the brazed on tooth would just drop off, but it didn't fall off, even when glowing red, so I cut it off instead.

Then tried my hand at brazing it onto my tool and struggled to achieve it.  I chose the wrong flux for one thing.  Cooked it to black and did not re-clean it, for another thing.  I may have also chosen poor filler rod.  Tried hard silver brazing after that, but without properly cleaning it, so that didn't work.  Then I grabbed some stainless steel wire and welded the tooth in place with that.  It stuck, so I left it.

The tooth is rectangular-ish and and didn't fit tight against the pin, so I used this diamond dremel bit to shape the inside of it and then heated it to red again and pinched it down on a pin.  

 

That was the first time I've used a V-block vertically.  Felt like an "ah-ha" moment.  As well as "duh".  Another blurry picture, but it shows how the carbide was getting closer to sharpened.

 

I wasn't being very patient that day and the failed brazing attempts made things worse.  I did try welding up a pin from a worn out distributor and then ran the new cutter over it, while holding the center post in my left hand.  The drill instantly spun the whole thing and I wore a bandaid on my index finger for a couple of days as a result.

 

I've not given up on this idea, but I need to shape the carbide on that cutter so that it cuts well from the end.  I think I can do that with some other diamond dremel bits I have.  I know it's a little nutty, but that's part of what makes it fun.  

Tom

[zinz]

Wow... this is Zen-Level Master Tinker stuff.  

['76mintgrün'02]

I found an interesting post on another forum where they were discussing condenser capacitance 

(it was on this site https://www.electro-tech-online.com/threads/automobile-ignition-question.114642/ )

 

A condenser with to much capacitance will cause a build up (metal transfer)on the mounting side of the points. A condenser to little capacitance will cause a build up (metal transfer) on the arm side of the points.

 

I opened my points up yesterday and it looks like the deposit is on the anvil side, not the hammer, so I guess I will try a different condenser, with a reading lower than the .23 micro farad one that's in there now. 

 

 

I'll remove the deposits and see if the crud sticks to the other side as a result.

Tom

 

 

['76mintgrün'02]

I made a little batch of hairpin clips tonight.  They are a wear item that have needed replacing in all of the early distributors I've opened up.

 

 

they wrap around the base pin and hold the center post's pin against the weight.  

 

 

I used some 1 3/8" 23 gauge micro pin nails that are just a hair thicker than the originals.  The wire they are made of is really durable. 

 

I was thinking I could make a fixture to bend them around and have each one come out the same, but wound up just using pliers.

I used the taper in the nose as a gauge for bending and marked the places that worked.  The first bend was .1" and the next three were spaced .15" apart.

 

 

with a loop bend mixed in 

 

 

 

I guess I can cross those off my shopping list.   

 

EDIT:  Those little clips cost $5.35 each at the Porsche store.

Edited April 2, 2020 by '76mintgrün'02

['76mintgrün'02]

I did a little advance pod mod today.  This was the first one I have come across that did not hold vacuum, so I figured it was sacrificial.   

 

There are (at least) two styles of mounting flanges on these pods and this one has the holes in the center of the tabs; but the ones that fit my 021 and 164 distributors have the holes in opposite corners, so I dug out the pattern I made and added two new holes beside the centered ones. 

 

I also noticed that the flanges are longer on the ones I use, but the other one was just long enough.

 

 

The little notch in the pod's shaft acts as the stop, limiting the amount of advance that it adds.  I wanted it to give more travel, so I extended it.

 

 

 

 

I nipped the head of a round head screw.  (I think it's a 6-32)

 

 

fed it through from the back side and tacked in in place

 

 

 

 

It still looks normal inside

 

 

and fairly discrete on the outside. 

 

 

I added a pointer so I could count the turns, to see how much advance it adds.  One full rotation equals two degrees on the tester, so four degrees at the crank.  That means every quarter turn of the knob adds or subtracts one degree of advance.  The adjuster offers ten degrees of travel on the tester, so twenty at the crank.  Putting it in the middle gives ten each way.  The spring inside the pod keeps tension on it. 

 

 

I could have put a notch in the tab at the end on the screw and avoided the weld, but I got lazy.  I've been wanting to do something along these lines for a while now and finally saw a simple-enough solution today.  I can't reach that knob from the driver's seat though, so  I  guess  I'm  not  quite  done  yet.

['76mintgrün'02]

 

 

 

 

 

 

 

[TobyB]

Ha!  That's fantastic!

 

Now I want to hide a little stepper motor inside, 

and give it computer controlled advance

(to go with that throttle body that looks like a DCOE)

 

t

 

[zinz]

Tom can market this as a "321Ignition"... ?

['76mintgrün'02]

51 minutes ago, TobyB said:

Now I want to hide a little stepper motor inside, 

and give it computer controlled advance

 

CompYOOters ? I think you're teasing me.  Although I was just noticing that the now-defunkt nipple would make a nice wire feed.

 

3 minutes ago, zinz said:

Tom can market this as a "321 Ignition"

 

These are actually 231 ignitions.  The one I am working on now is a 0 231 170 164.  

 

It was silly how much fun I had making the wing nut knob.  It came from the jack mount in the trunk of an e21.  

Drilling and tapping blind hole for a 6-32 was a bit tedious.  The bolt I used was kind of hard.

 

I couldn't resist making another one using a Subaru air cleaner wing nut, to match the three that hold my air cleaner on.

In the end, the first little black knob makes me the happiest.

 

['76mintgrün'02]

Last night, I assembled my new Bosch & Lomb spring tester.

 

It can test one spring at a time, or two, to see what the combination will do.

 

 

 

 

 

The caliper portion reads in increments of .1 mm and the brass scale is divided into 1/6ths of an inch.

 

MICRO adjustable weights

 

I am sure I will want something more precise, but it was fun to put this together.  It is sensitive enough to see a difference between these springs anyway.

 

I like that it breaks down into small components for storage.  The ruler is held on using cleco clamps and the handle is just a press fit into an 1 1/8" hole in the base.

 

I measured the spring post spacing inside the distributor at the shortest and longest spacing and this tester has a slightly longer range of motion than the advance mechanism asks of the springs.  

 

I've had this brass ruler for around 40 years!

 

Tom

['76mintgrün'02]

I set up a grinder with a thin wheel and a new tool rest that fits it, so I can refresh the worn mating surfaces on the weights and the base of the center post.  I was having trouble coming up with the fixtures to hold the pieces, so I decided to go the quick and dirty route and make the first ones out of cardboard.  I used CA glue on the pivot points and to secure the weights' post I made from a bamboo skewer.

 

 

 

 

 

You can see the little ledge worn on the foot in this photo

 

This is after the grinder smoothed it out

 

I made another little fixture to hold the center post.  Both fixtures have a strip on the underside, so they can be fed into the wheel following the edge of the tool rest.  This is the before photo.

 

 

 

I asked for some advice, concerning what curve I should shoot for and it was suggested that the total advance that the distributor puts out should be around 12 degrees, with advance coming shortly after idle and topping out between 2600-3000 rpm.  (That is actually on the long end of the suggested total advance).

 

I reassembled it and installed longer set screws in place of the original stubby ones I installed in post #1 of this thread.  (middle one)

 

Believe it or not, this thread is back on topic!  I used the advance limiting screws to reduce the total from 15 degrees to 12.5 degrees.  I used the protractor-tool to measure the advance and turned the screws in until I was at just over 12 on each side.

 

 

I put it on the Sun machine and spun it up to speed to confirm the total advance and then noted that the curve was starting at 800 rpm, so I reached through the access hole and bent the idle spring tab a little and tried again.  It hit 1 degree at 900 rpm, so I bent it a little more and it hits 1 degree at 1000 rpm now.  Here is the rest of the curve.  (ignore the red dots, they were an old curve)  This one is drawn at crank speed/advance, obviously.

 

I think I have put it within the suggested specifications and am eager to install it and take it for a test drive!  This will allow for more advance at idle while also dropping my total advance a bit.
 

P.S.  I have installed a .21 mF condenser on this distributor, to replace the .23 mF one I have now.  I am looking forward to watching the point's contacts to see where the buildup occurs this time.

 

Tom

[ray_]

Have you considered a software solution?

 

['76mintgrün'02]

Hi Ray!

 

I installed the 164 and ran some errands today.  It gives 25 degrees of advance and I have it set at 12 degrees at idle and 37 degrees all in.  That means bumping the timing light up to 12 shows the OT line in the peep hole and revving to all in at that setting shows the BB; since 12 + 25 = 37.  I thought that was kinda neat.

 

I wiped off the oily 021 that I removed and put it in the chuck to check the curve.  This shows why I installed the top of a Coke bottle.

This shows the date on the bottle, which happens to be the month/year that I found the machine.  Sort of like original equipment...

I used the same graph as the 164 to plot this one and noticed that it climbed really fast right around 2000 rpm and then went flat for the last two degrees. 

So I removed the points plate and installed the protractor. 

 

The protractor photo shows the weight being pulled out to the point where it gives seven degrees of advance and that point is marked on the graph above, by the top of the skewer.  Looking a the looped end spring, you can see how much the tab needs to be bent out to take up the slack and bring the spring into play at that point in the curve.  I actually set it to 6 degrees, instead of 7.

 

I caught that problem yesterday, after turning the adjusters in on the stops of the 164 and bent the tab out .050"; otherwise, the spring would have been loose until the last two degrees of advance.  Coincidentally, that was the same amount as the 021.  Another option would be a spring swap for one with a shorter loop, or bending that loop shorter, I suppose.

 

I wouldn't mind taking a few more degrees off of the 021 curve, but this photo shows the .030" or so that I'd need to bend the tabs in.  I am not sure I want to do it that way, so I will just have less advance at idle for a while longer.  

 

I put it back on the Sun and drew the new curve.  It dipped back down nicely, with the aid of the looped spring.

 

This probably explains the little bit of pinging I was hearing if I was lugging it around 2000-2500 rpm... not that I make a habit of doing that.

 

So, this one goes back on for another test drive.  That's the best part.

 

Tom