SU Float Setting Questions- Need yous help again z gurus

[spawpoet]

FINALLY we are back out on track following our rebuild, and mostly the car ran very well. Tim got his first race in, and by tomorrow should be one step closer towards pulling off those x's. He had very good drives today, and by the end of his race today was turning laps within 6.5 secs of the ITS leaders. That said we did have some fuel delivery issues, and I had a couple of questions.
I'm not sure we have the floats set properly on the SU's. As I understand it when the floats are set properly with the suction chamber/piston removed you should be able to see the fuel just below the bridge/nozzle interface down in the carb. I can only see the fuel in our nozzles if I open the chokes up. Additionally, I have to have the mixture nozzles turned as far rich as they will go to get enough gas for the car to run, and I still think it's a bit lean with them there. I CAN'T make it too rich with the mixture knobs. As it's set though we seemed to make good power until Tim was winding it out where it would lay down a bit at higher revs.
One last quirk was that a couple of times we had fuel overflow the bowls out the float lid vent. Is it possible to overflow the bowls, and have the floats set too lean at the same time? This would happen coming off of power where the fuel was backing up in the bowl. My guess on this was that fuel pressure was too high (4.5-5lbs) so we turned it down to 3.5 lbs, but haven't run at that setting.
The carbs are z-therapy units, and are in very good shape. Timing is at 34 deg total advance, and the ignition is working well. Plugs come out with a good burn on them, and there are no vaccum leaks. What really has me miffed is that I can't get meaningful adjustment in the mixture knobs. At full rich setting it runs, and anything else is too lean to even hold an idle. Any tips with this is greatly appreciated.

[pballance]

Just thinking out loud Chris, take it with a grain of salt..
4psi max. IIRC float level is ~12mm.
Yes, too much fuel pressure will over run the bowls.
Have you checked needle height?
2 1/2 "flats" should get the car to run and then you can balance and tune the carbs.
I have had the float level change when trailering the car and it caused issues.
Check for any vacuum leaks around the carbs.

Good luck, glad to hear it is back on track!

[spawpoet]

OK then I'm fairly confident that the overflow was from fuel pressure. We HAD a vac leak, but cured that before heading to the track (backfire out the carb blew out a throttle shaft seal). We set float level from the ceiling of the bowl cover to the top side of the plastic float at 14mm (setting per Clymers/Chiltons), so we will dial that down to 12 mm. Am I correct that the measurement is between the ceiling and top of the float?

If I set mixture at 2.5 turns it won't even keep running. It's just not getting enough fuel at the nozzle unless it's wide open. I'm gonna check the needle height tomorrow. And also make sure there are no clogs in the nozzle lines. Thank you very much for your advice Paul!!

[pballance]

Chris, it may be 14mm float level and you are measuring correctly, from lid to top of float. I was going from memory and would have to check the manual so you are probably right.

Check the nozzles and make sure they move up and down and make sure the choke lever isn't binding. I have one that is a little sticky. 20wt oil for the pistons, make sure you haven't overfilled.

Good luck, just some thoughts as I watch Auburn blow it at Georgia. Dang!

[tim240z]

Still had issues today but I think were figuring it out. I'll let Chris chime in with the details but we shaved another second off today. Even though it never really ran great for an entire session the car is coming along real well. Went 4 off for the first time today... that was entertaining. As far as PBIR... I love the track but they still REALLY lack in SCCA accommodations...

[spawpoet]

Chris, it may be 14mm float level and you are measuring correctly, from lid to top of float. I was going from memory and would have to check the manual so you are probably right.

Check the nozzles and make sure they move up and down and make sure the choke lever isn't binding. I have one that is a little sticky. 20wt oil for the pistons, make sure you haven't overfilled.

Good luck, just some thoughts as I watch Auburn blow it at Georgia. Dang!

Thank you again Paul. After reading this and going through some of the old related threads I'm pretty sure I have too much oil (it is 20wt) in the dampers. Ron said in another thread he used something like a medicine dropper to fill the dampers, and I just poured in. My guess is way too much. We adjusted the installed needle height (they were out too far) and I was able to get closer to normal mixture adjustment on the mixture knob. The biggest problem we are having is similar to Ron's from a couple yrs ago where in hard rt hand corners we have one carb's cylinders going cold (rich) on the egts, and the car misses badly til it burns off the extra gas. We have the bowl overflows vented back into the air cleaner assembly, and it's going rich when the bowls overflow I think. We are going to vent into a catchcan at our next event, and I still think our floats may be a bit high. Also we have N-27 needles in there which I believe run a bit lean, and I'm going to try the N-54's in there to see if it helps a bit more.

[Ron Earp]

Wish I could help you out but my carbs are a totally different design than your carbs. You've got external bowls and so on. Mine is basically like a big Mikuni carb - float on the bottom, piston, dampener rod, jet, needle. You've got to get your float height to a happy place though and that may not be the factory setting. My factory setting is fairly close, but not quite perfect.

And you've got to get the right amount of oil in the dampener section. I'm sure the 240Z guys could help you there, on the 260Z it is about 2ccs.