Datsun Roadster Forum-311s.org

I just finished installing my wide band O2 sensor and confirmed what i already knew, the engine is running rich (10 to 11) afr reading at idle. Pulled the domes to check and see if I could identify what needles are in there, wear, etc. Needles and nozzles look fine but I can't get one of the needles to come out of the piston so I can experiment with setting them out a few thousands, thus leaning things out at idle. Soaked with PB blaster, clamped in padded vise and pulled straight upwards HARD and it won't budge. I don't want to damage it. And yes, the grub screw is out, ha ha. U20 engine. No marking on the one needle to identify what it is....

Ideas?

Hey, glad the unit is working!
I would assume you have turned the dial that controls the nozzle height on the bottom of the carb all the way in/up, but it's still too rich? I don't remember how much you know about SUs... and I'm pretty limited. Is the base of the needle flush to the piston?

Try the Magic Number method for setting the nozzle height as described in the Tech Wiki to have a better starting point for adjustment of fuel delivery, as you dial in your AFR meter setup.

Linda

Reassembled domes, needles set flush with bottom of the pistons. At 1/2 turn out from closed I'm getting 13.1 afr so time to test drive. Thanks for the GloShift Greg, way cool tool! I have never run any of my SU's with a setting leaner than 1.5 to 2 turns out. I have ztherapy SSS SU's on my 68 wagon with L20b and will play with leaning them out some to see how the plugs/performance/gas mileage are affected in that car. I not only had a "stuck needle" in that one dome but also a stuck needle in my dome. Thanks for the help guys.

I'm really glad it's working well! They really are invaluable.

Was the stuck needle resolved?

No. I could not get it out of the piston no matter what I tried and did not want to damage it so just reassembled everything. I test drove and decided I was a bit too lean overall so settled on 3/4 turn out from bottom. Another test drive yielded 12.2 minimum at idle, 12.5 at wide open throttle and 15.5 to 16.5 at cruise in 5th. Pretty dang close to perfect according to this site http://afrplus.com/AFRplus-unit-functionality.asp.

The AFR made a 3/4 of a turn difference from where I started. The plugs were telling me that I was too rich but I had no idea if leaning it out would hurt the engine. The meter provided info and confidence critical to the tune. It idles about perfect, much better than any SU car I've owned and throttle response is right now and crisp.

14 to 14.7 for the majority of driving, shifting, etc. I could not be happier and now am a Greg Burrows advocate!! Gotta have a wideband AFR meter, yay!

Scott

Aw shucks (turning red)... really glad it helped... just passing on what I've learned... and I'm only wrong about half the time! I've honestly never heard of one using it for an SU set up, but it's really great to hear that the needles seem to be doing a great job of fueling throughout the range... pretty cool!

Correct. Now it would be cool to upgrade at some point to the HSR42 Mikuni's that Cromgnman on here says are hands down better performance wise to the SU's and use the Gloshift to tune those. Anyone seen $1100 bucks laying around? No? Oh well, I can always dream while driving what I've got as often as I can! And regarding that, boy are we having a mild winter here in Bozeangeles, MT. Probably will bite us in the butt later on....