Definitive 70 & 71 240z SU Fuel Level Thread

[240260280]

Here is all you need to know to set the fuel level in a fuel bowl for 240z from 1970 to 1971 inclusive (You will have to deal with the oddball bowl in the 72's however the FSM states that the fuel level will be the same in each bowl).

Below are two marks at 20mm & 23mm down from the top lip of the fuel bowl.  The FSM shows the fuel to be 23mm down from the roof of the fuel bowl(which is 20mm down from the top lip  but it may be a typo. Pick one and be happy.

 

 

The great Brian Little transposed the 23mm down from the top lip of the fuel bowl to a depth from the top of the bridge in the carb throat.  He came up with 10mm down.

I repeated the experiment below by using a telephoto camera shot to reduce parallax distortion and arrived at the same result.

 

 

 

Here is almost how you should measure fuel level with an installed carb. (I like to scribe a mark on the fuel bowl and use a long clear pipe Tee'd into the rubber line from the bowl to the jet).  I then press this line against the fuel bowl scribe and adjust the float tang to set the level).

 

The photo below almost has it correct but the hose is too far away from the side of the fuel bowl for accuracy. Also, there is no scribed fuel level on the bowl to use as a reference.

 

 

 

Here is better way to measure:

 

 

Here is the controversial FSM reference of 23mm down from roof of bowl:

 

 

Here is Brian Little's work:

 

 

 

Edited March 22, 2018 by 240260280

[jalexquijano]

This means for accuracy i will need the float sync one of this members developed and sells.

[240260280]

Just scratch a line on the side of each fuel bowl 20mm or 23 mm down from the top lip (you chose 20mm or 23mm).  Next, bend you clear hose down then over so that it  can be pressed against the line you scratched.  Adjust the float tang until the level in the clear tube matches the scratched line.

Basically just do what you are doing but bend the clear hose against the fuel bowl... do not have it so far away.

20mm down is very close to the top of that extruded block on the side of the bowl.  You can put a mark on that like I did above.

[Stanley]

Thank you, that photo with millimeter lines is helpful. I  was wondering how 20mm vs 23 mm from top of bowl question affects the 10 turns down at nozzle which the photo illustrates. I haven't decided on 20 vs. 23 yet, I want to check it with the sightglasses first since I suspect probably the rear fuel level is going too high at times causing intermittant flooding or rich condition, due to either too much fuel pressure or  a worn needle valve.

If the needle valve tip is OK I'll go with the 23 mm average since I definitely don't want it smoking or leaking gas. Since I have the later carbs I'll go with the 4mm front/rear difference per the tech bulletin, which makes it 23 average (from top of bowl), 10mm down / top of nozzle, and 25 mm down front, 21mm down rear (from top of bowl measured with sightglasses).  If the 20mm average down is really correct, I don't think using 23 down average will cause the front bowl to go dry since I have plenty of fuel pressure. It might cause problems for a racer going WOT around long banked turns but I'm not doing that.

[siteunseen]

I did 23mm from the underside of the lids. Balanced the two at about 400 rpms each I beleive. The rear is 2.5 and the front is 2.750. Runs great with no overflow and I've beat it pretty hard then popped the hood. No gas smell. I think I got 23 from zkars? He's who pointed out that matches the top of that rectangular boss on the side.

I did put two rear short ear lids on mine. Rear lid on the front carb too.

Edited March 21, 2018 by siteunseen