Something wrong with my Distributor?
 

My distributor does not seem to be getting its full advance.

It is a 1973 Bosch, on my 73.5 911 with CIS. It is a 0 231 169 008.

When I set it at 5* ATDC (with vacuum, 2* BTDC without vacuum), it maxes out at ~25* (without vacuum).

If I set it at 36* max, it idles at 14*. (both without vacuum)

I'm trying to figure out why my car runs great, except for light throttle, where it is not perfectly smooth - everything else is great. But that's a whole other thread.

Admittedly, my distributor has coming up on 200,000 miles on it. But the shaft has no discernible lateral play, and the rotor sure seems to spring back all the way. It does have Pertronix in it.

And I may ultimately ask if anyone has a good 73 distributor, or a 74-76 (0 231 184 00x) distributor I can borrow or buy. So feel free to offer that up if you do.

Set it at 8-10 at idle. 30-32 total should be fine.

Thanks. The question though is really, is this abbreviated advance curve showing that something is wrong with the distributor, so that I don't have the right advance at the right rpm. And maybe that's leading to my CIS not functioning correctly?

The driving issue is that at light throttle, it's a bit jittery, not terrible, just not perfectly smooth. And to get the rich/lean adjusted to be as smooth as I can, it causes the idle to be richer than should be. I've explored all other aspects of the CIS and I'm now looking for other possible culprits.

And note above, I had a typo in the ATDC, that is fixed now.

Have you clean and lubricated your advance mech?

Yep. I just plotted out the advance I am seeing. I can only assume this is showing something is stopping the second step of advance from happening.

http://forums.pelicanparts.com/uploa...1739844966.jpg

Here's a pretty good description on overhauling the dizzy of a 911SC. It may help you in some aspects although yours is a breaker points dizzy and rotating cw I guess...!?

https://nineelevenheaven.wordpress.com/maintenance-of-the-distributor/

I see there is not much activity on this thread. Have any members checked their advance to see if it met the original ignition curve? I have done some searching on Pelican to see if anyone has posted their ignition advance on stock engines prior to the Motronic cars, but only find modified cars with programmable ignitions.
Most of what I find is people saying either set it at idle, or for max advance at 6,000 rpm. I would think a bit of performance and efficiency is being lost by not making sure the spark is occurring at the right time throughout the rpm range. My original 0 231 169 008 distributor was replaced with a later 0 231 184 007 early on in my ownership due issues. The ignition advance was the same and 184 was in good shape, just a little more vacuum retard.
There can be a lot of internal issues with these old units, and many need more than just oil on the felt. Most fiber, phenolic pieces are worn out and need repair. Rust and corrosion limit movement.

http://forums.pelicanparts.com/uploa...1740695944.jpg

http://forums.pelicanparts.com/uploa...1740695944.JPG

http://forums.pelicanparts.com/uploa...1740696094.JPG

I can understand why most do not want to do the some of the repairs themselves, there are quite a few difficult to source pieces. They do seem to get easier to work on in later models. My 169 was a bit of a pain, the 184 was better, and my '86 930 602 023 00 was fairly easy.
http://forums.pelicanparts.com/uploa...1740696439.jpg

Personally, I think it's darn difficult to fully check the curve on a distributor without one of those fancy machines.

I have taken mine apart, cleaned it, fixed a bunch of small problems, and reassembled. My verification of curve function was to essentially verify advance at idle, advance at that "knee" at ~2000 rpm, and verify it fully advances at 6000 rpm. I just assumed linear advance progression between 2-6k rpm.

I swapped to a 123 distributor on my 1973.5 last year, it doesn’t look out of place and has worked really well so far. I went with the preset ignition curves as I didn't want to worry about the bluetooth option. It really woke up my midrange. My original distributor lost an advance spring on the drive out to Rennsport in 2023 and I had to cannibalize a distributor that I was able to pick up in order to make the drive home.

What is kind of nice with the 123 is I can wire it up without the cdi if that were to go out. I made a quick harness to keep in the car just incase.

No doubt it would be a lot easier with a distributor machine. Trying to check advance in the garage with a timing light on a running engine is a bit difficult. What you checked would pretty much be enough. Jay's check was missing the knee, as if one of the advance weights was not working.

Zuba, I think the 123 distributor seems like a really nice upgrade from what I've read. Is there any maintenance or occasional lube needed? I see a little info on the site regarding advance but no curve. I would think you are using #7 although 6 and 9 are identical. Do you have any more info about the curve? They show it at 30* max which is a little conservative.
http://forums.pelicanparts.com/uploa...1740779904.jpg

The 123 is a bit expensive, but reasonable compared to having a professionally rebuilt stock one that still needs points along with occasional adjustment. It's also good you can use without the CDI. They did seem mention that a different coil should be used in that case.

I set it to #7.

If you wire it direct(bypassing/eliminating the cdi you have to go to the 1.5ohm coil). The downside to that is the tach won't work. The coil fits in my tool bag better than an extra cdi box.

The directions are a little difficult to weed through, but I think I'm around 10k miles around it set up this way and have been enjoying it a lot

Just add a 5-10K resistor in series from the coil, with a .01uf capacitor to ground.