Bosch Distributor Refurb

The Bosch distributor on the 1800’s is part number 0 231 115 048 and is made of cast iron.  They typically remain in benign neglect since they apparently continue to work with no issues.   However the precision of your timing will be impacted by the play caused by wear in the moving parts, which is caused caused by all the dirt and grit.

There is a rebuild kit sold under the Bosch part number 1 237 010 007 for “2002 distributors”.  I purchased mine from 2002 AD since I could actually see a photo of the kit and its components.  I suspect this is the same kit sold under a BMW part number through BMW.  The kit is made to work with many different types of distributors therefore there is a large number of parts included not all of which are needed for a single distributor.  As well, many of the washers which appear to be the same are actually of different thicknesses since they act as shims to take axial play out of the rotating center shaft.

All parts in the rebuild kit

Here’s what the typical distributor looks like after years (decades…?) of duty:

Some distributors have c-clips inside the hollow cam shaft retaining it in place; not the 048.  You remove 3 of the 4 visible screws and the assembly pulls up: The screw holding down the points, the one retaining the points wire to the body and the screw holding down the vacuum advance shaft.  Remove the two screws holding the vacuum advance diaphragm housing to the distributor body and it pulls off.  You can now pull out the camshaft and the two plates sitting on top of it.  Those two plates are still held together by the black metal retainer under which there is a small steel ball.  This retainer is held to a vertical threaded eyelet with a screw.  Although my photo shows this screw off while the assembly is still in the distributor, it is much easier to undo this once the assembly is out.  Photos below will help visualize all of this:

Below is the camshaft assembly.  Carefully note the order of the three washers: Thick at the bottom, thinner and then the fiber on top.

Below you can see all the parts and the rebuild kit once they have been cleaned and some of them painted.  

Note that I have already removed the drive gear off the main shaft.  This gear is help in place by a 4 mm pin mushroomed at the ends.  It can be seen in the photo below.  The pin needs to be drilled out.  Be ginger when driving it out since you don’t want to be banging too hard on the main shaft and ruin the bushings it runs on.  This one had no radial play and I wanted to keep it that way.

The shaft, cleaned and de-greased with new shim and fiber washers.  On top of the shaft you can see the plate where the weights slide in and out.  The thin fiber shim provides a low friction, durable surface for the weights to slide.  Mine was not too worn out so I reused it but you can easily cut one of out of Teflon or some such modern, low friction material.

Here you can see the new red fiber washers included in the kit. They go on the weights pivot shafts as seen here.

Weights in place with new retaining clips

One of the weights (right on in the photo) has a longer shaft underneath that fits in an opening on the shaft plate.  This prescribes how much the maximum advance will be.

There is a rectangular piece of oil-retaining felt between the main shaft bushings set in place such that it forms a cylinder wrapping around the main shaft.  You can somewhat see it in the picture below.  It comes out easily and is surprisingly resilient as mine was in perfect condition and sturdy enough to be cleaned with dish washing soap and water and after dry, re-oiled with engine oil and put back in place.

See the felt between the bushings?

After the main shaft is in place comes the task of placing the drive gear back in place and re-pinning it.  The drive pin is spec’ed out at 4 mm x 20 mm.  You can find a roll pin this size at a good hardware store.  It will stick out about a mm on each end but it won’t hit anything.  If you hammer the new pin in you risk damaging the bushings and or shaft and introduce radial play in the main shaft.  This will be manifested as a difference in timing cylinder to cylinder (your timing mark jumps around when setting timing with a timing light).

Use an arbor press to drive the new retaining pin in.

Prevent the shaft from turning while pressing the pin in

This is as far as I could press it since the gear and distributor body get in the way of the press ram.

Use anything that fits in between to continue driving the pin.

The 20 mm pin is a bit longer so it protrudes about one mm on each end but this is not a problem.

Check for axial play on the main shaft. Should be .004. Not perceptible by hand.

Now the camshaft can go back in.  Those little springs are the key to accurate mechanical centrifugal advance.  If they get lost or overstretched, I have no idea where they could be sourced so be very careful with them.  Unless you have a vintage distributor testing machine the only way to test they are performing properly is with a timing light once it is installed in the vehicle.

Camshaft in place with springs attached to the weights.

Camshaft in place with new shim washers in place

The plate on the right is upside down so you can see the mating surfaces that slide to provide mechanical advance.

Both plates assembled and held in place with ball and black spring steel. Now the complete assembly can be slid in place over the camshaft. That's Bosch distributor grease on the steel ball.

In place.

Notice the small felt cylinders placed inside the shaft. There are two. This is service item. They should be oiled (engine oil) until moist but don't flood it. Use distributor grease on the cam itself. It is thick and fibrous so it won't fling all over the distributor.

Kit includes new felt plugs for the camshaft center. New vs. old.

This is the Bosch distributor cap that is now impossible to find. A bit of TLC and it's ready for some more service.

In place and ready to go!

The original style yellow wire capacitors are NLA but they seem to go for a long time. The new ones have a thinner green wire.

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5 responses to “Bosch Distributor Refurb

  1. GREAT PICS! ON THE PIC OF THE CAM ASSEMBLY, YOU NOTE A FIBER WASHER AND A THICK AND THIN SHIM; DO THESE SHIMS HAVE ANYTHING TO DO WITH SETTING AXIAL PLAY? WHAT IS THE PLAY TOLERANCE, AND WHERE IS IT MEASURED?
    YOU ALSO NOTE THAT .004″ PLAY IS MEASURED ABOVE THE TWO TOOTH DRIVING GEAR – IS THAT TAKEN UP BY THESE SHIMS, OR THE ONE NEXT TO THE FIBER WASHER ADJACENT TO THE DRIVING GEAR?
    THANKS leahrick1@gmail.com

  2. Rick,
    Thanks for your comments and questions. All of this should be evident to you when you take the distributor apart. The shims/washers that regulate the (.004) axial play are seen in the 11th picture in the post. They regulate how high or low the driven shaft sits.

    The 8th picture shows the three shims you ask about and these regulate the distance between the points plate and the rotating base. I don’t recall playing with those shims maybe just replacing them like for like. Let me know how it works out for you. What car are you doing this for?
    :Luis

    • Hi, thanks for the information.
      I have a bosch 022 distributor for my porsche 356c. i replaced this dist. with an 050 maybe 20 – 25 years ago, but the advance curve is different and i want to use my original again. i need another sdliding surface since i managed to crack it, and i didn’t have the foresight to take not of the shim arrangement when i took it apart.
      rick

  3. What an excellent step by step tutorial. Clearly stated with photos. Very helpful in my rebuild. Thank you for taking the time to help your fellow enthusiasts. RDB

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