RSR Marelli Distributor Rebuild

[Mr9146]

I know this may not interest everyone, but I thought it would be nice to document the rebuild of my Marelli twin-plug distributor. I decided to have the job done by Kurt at PartsKlassik (formerly Porschetechnik) because I've done some other distributor work with him and I have been very pleased with not only the quality of the finished product, but the speed at which he works. The work is fantastic and the turnaround time is reasonable which is great for a shop like ours which does a lot of tuning/service work in addition to restorations.

Anyway, I purchased this Marelli from a member of the forum as part of a small parts lot, and I knew going in that the distributor was going to be pretty thrashed and in need of restoration. However, it was worse than I thought, and I warned Kurt that he'd have quite a project on his hands. He seemed up to the challenge so I sent it to him and told him to, "Go nuts."

The aim is to do a physical refurbishment of the distributor so that it looks as close to new as possible, but we're also going to make it work better and update the internals with a setup from Pertronix.

So far, we're still in the tear down phase...here's some photos of what we're dealing with.

[andyjboy]

Great that you're sharing this info Marco - I'll be following this thread with interest.

[Mr9146]

Great that you're sharing this info Marco - I'll be following this thread with interest.

You're welcome. It's not often we get a look behind the curtain so I thought it'd be interesting to share...

[chris_seven]

I am intrigued by the shape of the 'cam' which seems to have 3 x lobes which is commonly used on the 6 cylinder Ferraris with a 180 degree rotor.

'My' S121 has a 6 point cam and 4 x sets of breakers and I would be very interested to know how the contacts, which appear to be magnetic are connected and fire the 12 plugs.



I have quite a few spares including bearings and am just water jet cutting new bob weights and making some other internal parts.

[Mr9146]

I am intrigued by the shape of the 'cam' which seems to have 3 x lobes which is commonly used on the 6 cylinder Ferraris with a 180 degree rotor.

'My' S121 has a 6 point cam and 4 x sets of breakers and I would be very interested to know how the contacts, which appear to be magnetic are connected and fire the 12 plugs.



I have quite a few spares including bearings and am just water jet cutting new bob weights and making some other internal parts.

Chris, both of my S121 Marelli distributors have the 3 lobe cam. Both are RSR big-shaft type (although the one in the above photo has been cut down for use in an early case) and use 4 sets of points ... two long wire and two short wire. The one that's currently installed in my '74 911 is unmolested and still running points, the one that Kurt is working on has the magnetic pick-up you see above.

If we can get Mike Moore to chime in about his Marelli we may be able to get a consensus ... do you have a photo of the riveted tag on the side of your distributor?

I also noticed your points housing has only two large holes while the one from my distributor has four. I'd love to see a photo of the inside of your distributor prior to disassembly.

[chris_seven]

My mistake,

I have two dizzies and one has a triangular lobe and 4 sets of breakers and the other has 6 lobes and 2 sets of breakers.and I bought the one with 2 sets if breakers as a bag of parts for about $300 - just over 5 years ago and have never had it running.

Now I have the 4 point dizzy I hadn't looked closely at cam and has just counted the 'bumps' whilst it was rotating.

All the breakers are 4 spring and long wire, which I guess are incorrect and I need to get a couple of sets with short wire.

The riveted tags is missing from the 4 point unit and is illegible from the 2 point dizzy.

Does this mean your RSR dizzy has 4 x magnetic pick ups and will you have to use 4 x Pertronix systems?

[Mr9146]

My mistake,

I have two dizzies and one has a triangular lobe and 4 sets of breakers and the other has 6 lobes and 2 sets of breakers.and I bought the one with 2 sets if breakers as a bag of parts for about $300 - just over 5 years ago and have never had it running.

Now I have the 4 point dizzy I hadn't looked closely at cam and has just counted the 'bumps' whilst it was rotating.

All the breakers are 4 spring and long wire, which I guess are incorrect and I need to get a couple of sets with short wire.

The riveted tags is missing from the 4 point unit and is illegible from the 2 point dizzy.

Does this mean your RSR dizzy has 4 x magnetic pick ups and will you have to use 4 x Pertronix systems?

I'm not sure how the magnetic pickup was set up, and I have no idea how the new Pertronix will be set up ... we'll see what Kurt comes up with on that one.

Sounds like you scored on one of those distributors though ... $300 is a fair price for any vintage, twin plug dizzy.

I have two extra sets of short wire points that would be correct for your 121. PM me and let's discuss a trade...

Keep in mind that the 4 sets of points is actually two sets of two. In other words, one pair upper and one pair lower. The pair is broken down as openers and closers ... I believe one set starts the charge and one set fires the charge. All the points are to be set at 19-20* dwell angle because, together, they equal the magic 38-40* specified for a single set of points.

I've bent Ed Mayo's ear about this a few times...

[Mr9146]

Got another update from Kurt today. He says the thing is pretty ratty and getting worse the deeper he digs. The distributor will require things like an overbore on the housing and a set of custom bearings.

Definitely clapped out race parts...

[chris_seven]

Even more interesting.

The S121 has a large deep Groove Roller bearing in the bottom of the housing and I doubt it will ever wear out as it is sealed.

The ones I have are perfect even after 45 years so the dizzy would never need a re-bore.

It looks as if the 'trigger' wheel on the left hand side of the top photo has 6 points which explains why there are only two magnetic reluctor devices fitted onto the base.

It all becomes clearer

[Mr9146]

Chris, I've asked Kurt for more detailed photos which he said he'll provide later today or tomorrow.

But, in the meantime, I would assume that because this distributor was so beat up that the bearing failed, hurt the housing, and now needs to be replaced. However, I've spoken to a few people and the general consensus is that the bearing is NLA, so a custom bearing will be made and the pieces will all be adjusted to fit together properly.

Looking at the first, most recent photo I posted it appears that the bearing is not sealed, or that the seal may have failed. Again, I'm not doing the job so I am relying on Kurt's explanations and photos. I will update with more specific info when I have it.

In the meantime, are you interested in the spare sets of short-wire points?