Distributor – upgrade or not
 

Hi All,
I'm about to restore my 71T engine. I will keep it more or less stock. I don't have to have a concours original look. Regarding distributor I have a few routes to chose from:

1) Restore my Magneti Marelli S112 BX distributor
2) Source a period correct Bosch unit
3) Get an 123ignition unit
4) Other?

Can you please give me some advice?

All the best,
Jörgen Forssling
Gothenburg
SWEDEN

Im seriouly considering a 123Ignition. I’ve search for examples and info in the Porsche world but can’t find any. The BMW and Datsun folks love them and share many different tune files. If we do choose 123 it will be a bit of uncharted territory.

Thanks for your input. So what do people usually run on their early 911 engines?

//Jörgen

Bosch here, in my 69T.

I have a stock one in my 79 SC. A few years back I took it apart and rebuilt it. The parts kit for doing that was pretty cheap, and it wasn't very hard. So rebuilding yours is probably a reasonable option.

Rebuilding may be an option, depending on what it needs and IF you can get the parts.

You might want to search for a good used Bosch unit, that would be my choice. Keep in mind that starting in '72 the size of the distributor changed.

Thanks for all input. Mine is just in need of some service. I need the O-ring at the end, cap, rotor, points and condenser. They seem to be out there.

My big concern is the springs for the advance. Hard to tell if they're ok. Also does anyone know if the S112 BX is ok for my 71T? Any distributor gurus out there?

//Jörgen

Maybe the gurus will chime in, but here is my $0.02.

If you can get the cap, rotor and points and your distributor is not junk you may be able to work with it.

Check that the main shaft does not have play. Either end play or side play, but turns freely.

If the springs are not corroded and the upper shaft that works the advance is free, you should be good to go.

You should be able to get the O ring from Porsche. The VR O ring I got recently was not very good. It was so tight it took a pry bar to remove the unit from the motor. I replaced it with the old original one and it does not leak. You may be able to find a standard O ring to work.

If parts are hard to find, or expensive and originality is not a critical priority...
 

You may want to consider a change to Bosch. Folks, like Jerry Woods and others may be able to sell you a recurved, serviced unit, perhaps converted to petronix to simplify your life.
Hth,
Chris

Thanks Gordon, appreciate your input. Yes, I want more gurus to chime in! All in all, I can start with this setup and upgrade later on.

Chris, I've seen the refurbished Bosh units go for big $. If not concerned with originality I think I will look into the 123ignition units.

When going modern/digital/no points will you still run the CDI unit? I have not really understood its function in the setup.

Thanks for all input!
//Jörgen

With 123Ignition and CDI the distributor is wired similar to a Pertronix exiter. 123 handles the advance curves signaling the CDI to discharge the coil. The reason I’m interested in using it is because it falls between a rebuilt distributor and full coil on plug computer controlled ignition. You get the benefits of configurable ignition with less cost and an easier installation. My car has a hotter cam. I’m pretty sure the distributor was not recurved. 123 can solve that problem. My distributer has vacuum, the 123 allows setting timing for both RPM and vacuum.

I'm with Chris - if I was looking at this, I'd seriously consider the 123 - here's why:

Restoring the Marelli distributor would keep your car more original and more unique. But if anything goes wrong while you are out on the road or taking a trip, finding parts would be a real challenge.

Switching to a Bosch unit is what everyone used to do. It's the natural replacement, and would most likely work just fine. You'd still have make sure the advance is working correctly and play with the springs to get the correct advance curve for your setup.

A 123ignition unit is a modern upgrade that would eliminate the need to re-curve your distributor or worry about whether the old parts are working correctly.

Don't get me wrong - I like working on my car - but replacing the points with a Pertronix made my life better. Replacing the Bosch CDI with an MSD made my life better. I think getting a 123ignition unit would be the next logical step.

I don't think most people realize how much performance they are missing by not checking to see if the throttle is all the way open when the accelerator pedal is pressed to the floor, and those that don't advance their ignition as much as possible. The 123 unit would allow you to get the correct advance curve without too much trouble, and without worrying about whether the old part are working correctly.

Thanks guys! I'll give this some thought. I will soon start working on the engine and it will be some time before I can turn on the ignition...

All the best//Jörgen

As long as the bearings are ok you can lock the distributor and fit one our CDI+ units. Fully programmable with an electronic ignition map and rev limiters. You won’t have to do any wiring changes and your car will look standard. Works with original coil and plugs too.

My shop told me that the 123 is the way to go. I'm having it installed this week in my 79 3.0 and will report back.
Mike

I got my car back last week and immediately noticed the difference when pulling away from the shop. They set it up with the standard "S" curve, power was smooth and more responsive, honestly much more than I expected. Loving it so far and having the ability to disable the car via the Bluetooth app is just icing on the cake.
Mike

Installed the 123 this weekend. Only had time for a quick test drive. The car seemed to be stronger. I still need to adjust the webers and take it for a serious drive. Although the instructions were obtuse, it was easy to install. Find TDC. Remove old distributor. Install 123. Line up the rotor to cylinder 1 on the cap. Turn distributor until the green LED comes on. Put the cap on. Cable up the plugs. Start it up.

To figure out the advance curve, I read every post on this forum. I picked one that looked promising. I limited max advance to 32 degrees. I had no luck with the vacuum curve. Most folks said take it off. I want to see if I can use it to my advantage. I’ll need to study it more. Until then I zeroed out the vacuum curve

So where does this fit among all the choices there are? I really like what Clewitt and Ransant are offering. Full ECU control and coil on plug is probably the ultimate ignition. I like to drive my car
though. Futzing around with block mods and cabling to the cabin seemed is beyond my willingness as a do it yourselfer. Im not welding a bung on the exhaust for example. For me it is a great solution, I got a wobble-free distributor and am able to set advance curves without screwing around with weights and springs.

Installed 123Ignition on 911 2.2T 1970

http://forums.pelicanparts.com/porsche-911-technical-forum/1027517-123ignition-distributor-3.html#post11130653

Got a Marelli rebuilt, put back into my 70. runs like a champ. Get yours checked on a machine to make sure the curve is good, no excessive play and its fine....

its the curve that is the key. I'm liking the 123I units before they came out. i recurved an SC 3.0 unit with a true mechanical advance (no vacuum) and boy did that make a huge difference to the engine. Along with carbs, ssc backdate. but the ignition was the single most bang for the buck if you will to aide seat-of-the-pants feel.
along with MSD Al-6 and a Blaster coil and new wires makes for a great package