Ignition questions - Jekyll & Hyde 911

[Hi_Fi_Guy]

Purchased a 71 911 T that had been sitting for over a decade. Car is a 2.2 with Zenith carbs. Between myself and a reputable shop took care of the normal stuff. Compression check, new plugs, plug wires, valve adjustment, new tensioners, replaced some leaking seals/covers. Etc. as well as new fuel pump and all new soft fuel lines.

Took the car on a 3000 mile road trip and noticed a few issues with the car. My plan is to refresh each system one at a time and get the car running and driving as good as it looks.

One issue is low RPM running. Car pulls strongly above 2000 RPM and runs like a champ 3000 RPM and above. However when taking off from a stop the car makes almost no power and wants to bog down in 1st gear or when driving slowly. I have to feather the throttle to get it to 2000 RPM and once it hits that magic number it lunges forward with plenty of power. It really behaves like 2 different cars, one that doesn't want to run in around town stop-and-go driving, and another that hums along fine on the freeway and back roads. The car has a bit of a Jekyll and Hyde personality that way. Along with the weird no-power below 2000 RPM situation the car wants to die when stopping at intersections.

Anyone else experience these problems and have a proper diagnosis?

With the car so old my guess is the low RPM problems are a combination of ignition and carb issues so I plan to sort out the ignition first before doing anything else. Car has points with CDI. I plan to replace the CDI with an MSD + new coil in the hope of better running at low RPMs. However there seems to be little to no consensus about changing the points to for Pertronix, leaving as is... or some other option for triggering the MSD.

FYI: Distributor-less ignition is most likely not in the budget unless that's the only viable solution to make the car run correctly.

Thanks in advance for any and all replies. I hope to get the ignition sorted and do some driving to see if any of the symptoms go-away/change before rebuilding the carbs.

[rwest]

I have very little experience with carbs, but I’m betting it’s not an ignition issue, although having ignition in tip top shape is always a good idea and usually not costly. I have the MSD 6AL, blaster coil and standard points. Works great, replace cap, rotor and wires and then make sure timing is set and properly advancing then start looking at the carbs. My teeny bit of knowledge points to the idle jets/circuit as they would be working in the low rpms.

[jpnovak]

Is your mechanical advance in the distributor working properly? You can verify with a timing light at the same time you verify the timing spec.

Have you removed and thoroughly cleaned the carbs? Set the idle balance and idle mixture? Then properly balanced the linkage?

What you describe is classic description of the idle circuit not working properly on the carbs. The transition rpm is a 2600-3000 rpm going from idle to mains. No fuel (or too much fuel) will make them bog and then catch up.

Since the car is unknown and sat for a long period of time I would remove the carbs, carefully disassemble and clean out every passage, float bowl, jet, etc. It will make a huge difference. While you have it apart, verify all the jet, venturi, air correction and emulsion tube sizes to make sure they are appropriate for your car. Just because you think it is original doesn't mean it is after 47 years.