I’m going to text him tomorrow and see if he’ll get back to me. I actually have the stock needles from my original carbs now that I think about it. I’ll try swapping them in tomorrow while I’m waiting for Jeff to get back to me. 

Swapping in a pair of known stock needles would be a good test, and something relatively easy to try.

I know you said you are already positive that your float levels are on target and your chokes are not sticking down at all. And with those two things not causing a problem, I'm having a hard time coming up with a scenario that would result in running rich without some sort of damage to a nozzle or a needle or a wrong part installed.

Like I said, lean is easy. Rich is more difficult assuming you have already ruled out the easy ways to run rich (float levels and sticky chokes).

What is the history of the nozzles?

And who did the alignment of the nozzles after the rebuild process? Is that something you did, or did they come to you already aligned?

I got the carbs and intake manifolds from Paltech and just bolted them on as-is.  I really have no idea what their history is, as I just bought the full set from him rather than having him restore my originals. I’m assuming he aligned the nozzles. The pistons drop freely with a nice solid clunk at the bottom when I pull the oil damper out, so I’m assuming the alignment can’t be terrible right?

I’m going to swap those needles in an hour or two and I’ll post an update. 

Like the Captain said it could be the nozzles too. If you have a couple of good matched sets, you might want to swap out both

As well as identifying what needles are in there, it may be a good idea to see if the nozzles are stock 100s. I see that Ztherapy sells different diameter nozzles. I know little about the different nozzles available or how to identify them, but if the PO installed larger nozzles it would run pig rich.

I just tried pulling the needles out of my old SUs, but both needles were stuck hard in the cylinders. I ended up just dropping the old cylinder + needle combo into rebuilt carbs on the car and ... drumroll ... it runs much better!  The car won't start anymore with the mixture screws all the way in, but runs great around 2 turns down with a nice blue-ish spark from my colortune. I'm very pleased.  I'd like to get a new set of needles if possible - does anyone know a good source these days? It looks like MSA is out of stock on their N-27s. 

 

By the way, here's what the needles I pulled out look like - the pitting is worse that I had thought, and I'm guessing that was effectively "thinning" the needle causing the rich condition:

 

Well I may have celebrated a little prematurely. I had only color tuned the rear carb before my last post. I just went out and tried tuning the front one and it’s still rich, even with the mixture cranked all the way in. 

If I needed needles it would be Ztherapy

Good idea. They don't have them listed on their site, but I'll give them a call and see. 

Beware! Some 240z repair kits with gaskets and needles sold for early 240z are too rich.  The needles may be made for later 240z with flat tops or even another SU application such as the roadster. Both @Captain Obvious and I had these. The rest of the kit was ok.

Did you swap the pistons and tops or just the pistons?