Mixture setting

[rclayton12]

I have done my conversion from flat tops to SUs on my 1973 240z. I have removed the air pump and the egr valve and cleaned it all up with a 240 style balance tube. I was wondering for the other Z owners who have done this same conversion what mixture setting they run. I know the Ztherapy video says around 2 1/2 out. I also have upgraded with msd ignition with the zx dizzy. I am concerned that I am running rich when I regapped my spark plugs the other day and they were all black. I also am only getting about 19 mpg. What setting do you run on your SUs?

-thanks

[Arne]

The number of turns we all use will vary depending upon the exact float level per carb. For example, my carbs are about a half a turn different from front to rear. No two cars are likely to have the same settings, even if they are identical set-ups. The 2.5 turns out is a convenient starting point, you need to fine tune both carbs independently from there.

[beandip]

Reclaton , There is a article on the adjusting the SUs and I think you will find it if you do a search for adjusting SUs. Arne is correct the 2 1/2 turns is a good starting point to get you up and running . Do you have a flow meeter to balance the two carbs air flow ? I bought mine at the local parts store for about $25.00 , they have a performance section . mine is a uni-sen and packaged by Edelbrock . A device to balance the carbs is a must . I does sound like you are running rich , you should be getting up in the 20s for mileage . If you do replace the needles , get #54s , I think you will be satisfied with these . These are still available from Nissan . But do check the search because there is a step by step on adjusting these carbs. Gary I just tried to find my article on this and couldent. Send me a PM on this and I will go over it with you .

[rclayton12]

The carbs I bought were from Z therapy, and I installed them in late April I think. I do have the flowmeter and can balance them, but don't you only use it when using the idle screws? How do you adjust the mixture independently?

[wfl_colorado]

No. You use the flowmeter to help adjust both the mixture and the idle screws. Then once you have the idle right, you move to high rmp ~3000 and adjust the balance screw. Do you have the tape from Ztherapy? If not, I can explain a bit more since I just went through this. Let me know.

Bill