I've torn apart both carbs in search of an answer. This is after messing with tuning for hours, and not getting good or repeatable results. I've read different things about how to tune the mixture. Some say the results of lifting the pin to raise the piston shows the mixture of the other carb. Some say lifting that pin shows the mixture on that carb. Either way, I wasn't able to get understandable or repeatable RPM change results to make heads or tails of anything. So I ripped them apart. Here's what I found.

Front SU Carb



Rear SU Carb



As you can see, the rear carb's jet is longer than the front. Both needles appear to be the same. Would different length jets make these carbs pretty much untunable?

Another observation not shown is that after running the car a long time, then shutting it off and removing the piston and needle assembly, I had fuel pretty violently percolating out of the jet. I had to keep the needle in there to keep from loosing lots of fuel. It would do this for 15 minutes after shutting off the car. The rear jet didn't percolate at all. Am I boiling my fuel in the float chamber?

I can't find any identifying marks on the needles or the jets.

I checked everything else I could think of. The float chambers and floats themselves look in good condition. Neither float was leaking, and they both appear set at the same level.

At this point getting matched jets seems the logical step, but I'm not sure how to proceed. I'm trying to assess the condition of everything and figure out how deep a rebuild I want to go. Should I consider a complete rebuild at this point?