SU Float Setting Questions- Need yous help again z gurus

[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.

[spawpoet]

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.

Ron, was it the float height that was causing you to have one carb's egts going cold Ron?? I have the bowl sight tool on order from z-therapy, which should give us a little more accurate look at the float settings. Actually what you've said is a help. I've been trying to religiously follow factory settings, but it's helpful to know we might have to drift a bit from stock specs to find what's going to work for racing. Moreover I just never realized that the amount of oil added to the dampeners was all that important. BTW have you run your car with the new motor in it yet?

[MIKEL]

We ran 3in1 oil vs 20wt also look into diff spings in the dampners some of the english stuff is lighter than nissan. Also look into custom ground needles the two you mentioned will leave you fighting lean a lot(they are designed for mid range response). Remember most of the time you are at full throt. and slowing the piston will only help at low rpms and makes response slugish in the higher rpm range.
The MG guys can tell you where to get the light wt springs and several people have custom ground needle sets cheap or if you are talented try your hand at grinding your own (we modifed a set of english ones for our autocross car back in the day).
I think you will find at top rpm is when you are leaning out and either the needle profile is wrong or you are not getting full piston travel. On the EP car we dont run any oil and just use the spings for idle, pistons go wide open at 1500 and have the needle profle set for the cam. We run 7400-8000 on 3.5 psi pressue and have no problems with lean out.

[Ron Earp]

Ron, was it the float height that was causing you to have one carb's egts going cold Ron?? I have the bowl sight tool on order from z-therapy, which should give us a little more accurate look at the float settings. Actually what you've said is a help. I've been trying to religiously follow factory settings, but it's helpful to know we might have to drift a bit from stock specs to find what's going to work for racing. Moreover I just never realized that the amount of oil added to the dampeners was all that important. BTW have you run your car with the new motor in it yet?

With respect to one of the problems I fought for a few races I had a carb that was a bit off on the float setting and the fuel level was too high. I have sight glasses but the carb that had the setting off had a poor glass that didn't allow you to see the level. After resetting the floats many times I finally got my hands on proper glass and fixed the problem. I then further fixed the problem to make it easy to set the floats by using a "go no go" wire gauge inbetween the float tab and a fixture cast in the bowl so I don't have to worry about it - I set it with the wire gauge and I know it is good. I arrived at the proper setting by using the carb that was working well as a master.

Damper oil - Steve P and I have compared notes here and both of us agree that no damper oil doesn't work well. It worked well on Sam's dyno, but on track having no damper oil seemed to allow the pistons to slam open quickly and we both experienced throttle transition stutters. Bear in mind Steve has a 240, I have a 260, but we both had the same experience.

Too much oil, like filling the tube 2/3 full or higher, seems to cause a bit of a sluggish response. I know that description is hard to quantify but that is about the best I can do.

Mine seems to like about 2ccs (2 mL), and I use 20 weight motorcycle fork oil (I don't think this makes such a bid difference, you just don't want a multiviscosity oil in there). Why 20W motorcycle fork oil? It was what I had on the shelf that was single weight. I'm sure you could get similar results with 30W motor oil.

We have run the new motor on the track but not the dyno. On track I think I think what we have is a bit more hp throughout the range than the old motor. Beyond that they seem somewhat similar. I'm looking forward to putting it on the dyno and actually getting out and doing some racing with it!

[dspillrat]

You do need springs, you do need oil. Withoutem piston slams open at slightst throttle opening.......throws mixture outta whack...IMHO.
Try a little lighter weight to 5-10 weight....YMMV.... Yeah, and hope Katman will throw his 2 cents worth in.....

david