1972 Float Adjustment ...

[psdenno]

Just when I thought we were nearing closure. 

Dennis

Edited March 14, 2018 by psdenno

[siteunseen]

Oh no!  He changed the color of the STOP sign. 

[Mark Maras]

4 hours ago, 240260280 said:

Also, I am not sure if 1/16" inch below the jet nozzle at 2.5 turns down is correct.  Here is what one expert measured... 10mm down from bridge.

 

So  top of fuel will be at 10 turns down.

 

 

@Bruce Palmer @240260280 @jalexquijano and all others who are interested. Hopefully we can get to the bottom of this. My experience with SU's for a few decades was with 4 screw carbs. When I set my floats using the 9/16" method, the fuel level turned out to be a bit below the nozzles at 2 1/2 turns, although checking the fuel height in the nozzles was more out of curiosity back then. Decades later, someone quoted Bruce saying the fuel level in the nozzles was supposed to be slightly below the nozzle top at 2 1/2 turns. I had no problem whatsoever over the years with my SU's and that confirmed my findings from years ago. I was convinced that the 1/16" at 2 1/2 turns was correct. I'm still pretty sure that's correct but I'd like to erase the little bit of doubt I have. I don't give a damn if I'm right. The import thing is to figure this out so we all understand it. 

[Stanley]

Allow me to drop another worm into the can. I copied from the "Technical Information Page" tuneup procedure. This procedure is also in ZTherapy video. I think it may apply to those using SM's or other British SU needles more than those using stock or modified Hitachi SU needles, due to the 0.099 station 1 dimension vs. 0.095 for Hitachi.

After passing this on countless times via email, I figured I'd post some info on setting the needle position. Many of these cars have been around the block a few times, so often times, the carbs are way out of whack - too far to straighten out with the above procedure. F'rinstance, when I got my latest "70" 240Z, the rear carb was about five turns out, whereas the front carb was at around two. Yikes! So, when you encounter something like that, or when you just can't get them lean enough, try this:

Warm up the car.

Shut it off and remove the carb domes (take out the dipsticks first).

Remove spring from dashpot (the piston-thing that lives inside the dome).

CAREFULLY remove the dashpot - see the needle on the bottom?

Loosen the set-screw that holds the needle so that the needle can move a bit.

Turn the adjusting nuts all the way in (located underneath the carb throat, where the fuel line enters from the float bowl).

Pull the needles out about 1/8" or so, you should see the shoulder of the needle sticking out past the dashpot body.

CAREFULLY reinstall the dashpot, and push down ever-so-gently to seat the needle fully in the nozzle (that's the hole the needle sits in).

Pull the dashpot back out, snug down the needle set screws, and put them back together.

Set the balance and mixture as above.

[Mark Maras]

That's not another worm in the can. I use that method to set needles too. Another worm in the can is when we start pulling the SM needles out of the pistons a bit to clean up the idle. But that worm is down the road.

[Mark Maras]

@rossiz You rebuilt your carbs a few years ago and your Z runs great. Where is your fuel level?

[Mark Maras]

 Found it. '72 SU Float Level 2/20/12. "When all is said and done and the nozzles are where ya like' em, the fuel level as viewed down in the nozzle should be about a 1/16 of an inch below the top of the nozzle. Puddling up on top of the nozzle, things'll get fat and contrary to that if the fuel level is too far down the nozzle things'll be lean." That statement comes from Bruce Palmer. If "where ya like'em" is 2 1/2 turns the fuel level should be 1/16" or so below the top of the nozzle. There's no way, IMO, that the fuel level is supposed to be 10 turns down UNLESS the 10 turns down (23 mm) fuel level is with the float removed. The fuel level raises 7 1/2 turns when the float is installed putting it at 2 1/2 turns down. Anyone?

[jalexquijano]

i guess that with a set of pictures of both of your carbs at 2.5 turns i could undertand better what do you mean by "1/16th below the nozzle".

[240260280]

10mm down is from Brian Little.  He is my Z hero so I believe him.

 

See his work here: http://datsunzgarage.com/engine/

[siteunseen]

16 minutes ago, jalexquijano said:

i guess that with a set of pictures of both of your carbs at 2.5 turns i could undertand better what do you mean by "1/16th below the nozzle".

Use your imagination but this is close to what you want.

 

[siteunseen]

This is a mo betta visualization. Didn't have any food coloring.

Edited March 16, 2018 by siteunseen

[Mark Maras]

1 hour ago, 240260280 said:

10mm down is from Brian Little.  He is my Z hero so I believe him.

 

See his work here: http://datsunzgarage.com/engine/

@240260280 I read Brian's write-up on setting floats 10 turns down, 23 mm fuel level. All seems good until you read his opening paragraph under "Setting SU Float Bowl Levels". He says 2 1/2 turns down is the proper setting. Note in his instructions that he doesn't return his mixture screws to 2 1/2 turns. It can't be both ways.