I took Sunday to try to restore the Marelli S112BX distributor I bought off eBay. There isn’t a ton of info out there are these distributors, but I was able to find some help. PartsKlassik offers a rebuild kit, which is great given that parts were hard to come by for some time. It doesn’t come with any instructions though. There is however a pretty decent document and video on Klassik ATS.
Note that this distributor doesn’t have a condenser. More about that in my 914-6 distributor WTF post.
The key areas of concern I had when going through this were:
- Not enlarging the hole when drilling out the gear on the retaining pin
- When media blasting, keep debris out of the main shaft where oil circulates
- Keeping components from rusting after cleaning, as media blasting will remove protective coating (i.e. zinc or cad)
The kit from PartsKlassik was pretty good. A few things to note on it:
- Doesn’t include the felt used to retain oil. I was surprised to learn from them that they don’t replace this when they do rebuilds.
- Doesn’t include the tiny plastic bearings that snap into the weights
- Doesn’t include what I think is a phenolic washer that I believe is meant to go between the drive gear shims and the body
- Nothing is labeled (i.e. which bolts go where, but there aren’t that many components)
- Does have a nice selection of shims to set the gap between the gear and body
I ended up glass bead blasting the metal components. On the main body. I wanted to keep media out of the main shaft, as oil circulates through there. What ended up working great was rubber leg tips bought from the hardware store. 1 x 1-inch and 1 x 5/8-inch. The shims are quite thin, so if you hope to reuse those you shouldn’t blast them. They will warp. You also want to snap out the plastic bearings from the weights.
I took a bit of a risk with the weights and plates. I expect they were zinc coated and once I blasted them, that protection was gone. I really couldn’t see sending less than 10 small pieces off to the plater. I ended up coating these lightly with white lithium grease, hopefully that will cover it (bad joke intended).
The shaft was stained and pitted even after blasting. I ended up trying to polish it with 3M Scotch-Brite maroon very fine pad. See my post on questionable use of tools for how I tried to shorten the time on that.
In reassembly, it’s important to be mindful that this is an aluminum body. If you strip the threads for the bolts that hold the points for example, you will be sad. I originally thought I had done just that, but I had picked the wrong bolt and it was too short. Now I know why the previous owner hadn’t used washers!
Ultimately, it came out pretty good. I will send it off to someone with a distributor test machine and hopefully it will come back within spec. If not, I learned a lot about the distributor, but also burned about $350 in the core and kit.
