1972 Float Adjustment ...

[Stanley]

Found it, posted couple years ago. I was wrong it's 4 mm difference not 3. Still not clear how this relates to the 23 mm down from the underside of the lid measurement. Fig. EF-47 in the FSM shows a dimension "H" = 14 to 15 mm, that's almost but not exactly like the measurement of 11.5 to 12.5 mm rear, and 15.5 to 16.5 mm front in the tech bulletin. Fig. EF-47 shows the dimension from the underside of the lid to the tang on the float, while the picture in the bulletin shows it from the lid to the outer surface of the float. No big deal I guess.

0.55 inch = 14 mm     15.5 mm = 0.61 inch      11.5 mm = 0.45 inch
So maybe make the plastic 0.61 for the front and 0.45 for the rear.

TechnicalSupportBulletin-TS73-10.PDF

I still think that method's iffy. Too dependent on fuel pressure and the action of the valve. Maybe the new valves with the skinny pins react different. BTW, the pins in the new valves are kind of wobbly and will stick open if the tang on the float isn't flat enough. Too much curve in the tang is bad. Maybe it's possible to substitute the pin with an old type pin, with the other parts new. Haven't tried, might not work.

Edited February 23, 2018 by Stanley

[DaveR]

3 hours ago, jalexquijano said:

Until this moment nobody has come with a precise response regarding from where to where is the .55 inch, 9/16  or 14mm measured? Is the measurement taken with the tang barely touching the neddle pin or with its weight on.  I measure it with the tang barely touching the needle pin and the mixture at 2.5 turns clockwise is still lean. Please see my post #156 for pictures as reference. Am i still to lean? Should i lower it?

There are solutions posted that don't require anything but an initial ballpark for the float position. This is what I had to do. I would suggest not even bothering with a measurement, and instead install it, fill the bowls and see how high they are. Then adjust the float up or down and repeat. This is the only way I could get mine properly set, and I well understood why my original measurements weren't working.

Bite the bullet and forget about the 14mm etc. I stand by the 10 turns approach and set as I detailed above. This didn't originate from me, but it did work well for me. 

Edited February 23, 2018 by DaveR

[DaveR]

2 hours ago, Mark Maras said:

 Someone correct me if I'm wrong. I'm assuming the 10 turn down method is viewed with the float cover removed and the 2 1/2 turn down method is with the floats installed. More assumption now, that would mean the installing the lids (floats) would raise the fuel level in the bowls about 7 1/2 turns. is this a correct assumption or am I missing something?

Fuel adjustment all the way up. 

Turn it down 10 turns with everything assembled except the domes and pistons. 

Let the fuel pump fill up the bowls without the car starting.

Check the fuel levels relation to the top of the nozzle by eye shining a flashlight in.

If it's above the top of the nozzle, remove the float lid, bend the Tang in correspondence with raising or lowering the fuel level, suck out some fuel so it's back below the nozzle top.

Reinstall float bowl top.

Run the fuel pump again. Check. Repeat until done. You want the fuel level right at the top of the nozzle hole and right on the verge of flooding the top on the nozzle which is now 10 turns down into the bushing. You want the fuel to remain down inside the nozzle but right the the top.

I unplug the dizzy and use my starter motor and battery to cycle the fuel pump and check what it fills to.

After you are happy with the level... Reassemble everything. Undo all 10 turns so the fuel adjustment is at the top. Then go down 2.5 turns and use that as starting fuel level for tuning.

Edited February 24, 2018 by DaveR

[DaveR]

2 hours ago, siteunseen said:

Turn the damn thing over blow lightly into the fuel inlet tube while moving the float toward the lid. When the needle closes you should feel resistance to your breath. That's where your measurement should take place. Bend the tang on the float to get that gap from the top of the float to the bottom of the lid. Once you get both set the same, put your hands in your pockets and back away.

For what it's worth I tried this before my above method and it wasn't as accurate as I liked... But it was better than a blind guess. I still prefer the check and adjust with the nozzle 10 turns down

[jalexquijano]

22 minutes ago, DaveR said:

For what it's worth I tried this before my above method and it wasn't as accurate as I liked... But it was better than a blind guess. I still prefer the check and adjust with the nozzle 10 turns down

Front and rear fuel levels after adjusting tang.

[Stanley]

I see you hooked up the sightglasses. Just bend the plastic hose and hold it vertical right against the side of the float bowl. Get a pencil and draw a horizontal line on the float bowl that lines up with the fuel level. Then do the same with the other carb. Get your micrometer and measure the millimeters from the bottom of the lid (or the top of the bowl plus the gasket) and write it down. Then check the other one and write it down. It should be about 25 mm down for the front one and 21 mm down from the lid for the rear.

If it's close then you're ready to fine-tune it with the "nozzle" method. If it's Within 1 mm it's close enough since the fuel level goes up and down that much when the engine is running, as the float valve opens and closes. If you watch the sightglasses carefully with the engine running you can see that happening. Use the nozzle method for the last stage since it's the most accurate. Also with the nozzle method you don't need to think about the fuel in the front bowl being lower than the rear. They should both be the same level in the nozzles.

If you check it 10 down in the nozzle and they're both very close to right, then you're done. Don't get carried away getting it perfect. You can get almost perfect, adjust the tang very slightly, and just make it worse. In fact the process can be described as "make it better, make it worse, make it better, call it good". Just make sure you "call it good" after making it better, not after making it worse.

[jalexquijano]

14 hours ago, Stanley said:

Found it, posted couple years ago. I was wrong it's 4 mm difference not 3. Still not clear how this relates to the 23 mm down from the underside of the lid measurement. Fig. EF-47 in the FSM shows a dimension "H" = 14 to 15 mm, that's almost but not exactly like the measurement of 11.5 to 12.5 mm rear, and 15.5 to 16.5 mm front in the tech bulletin. Fig. EF-47 shows the dimension from the underside of the lid to the tang on the float, while the picture in the bulletin shows it from the lid to the outer surface of the float. No big deal I guess.

0.55 inch = 14 mm     15.5 mm = 0.61 inch      11.5 mm = 0.45 inch
So maybe make the plastic 0.61 for the front and 0.45 for the rear.

TechnicalSupportBulletin-TS73-10.PDF

I still think that method's iffy. Too dependent on fuel pressure and the action of the valve. Maybe the new valves with the skinny pins react different. BTW, the pins in the new valves are kind of wobbly and will stick open if the tang on the float isn't flat enough. Too much curve in the tang is bad. Maybe it's possible to substitute the pin with an old type pin, with the other parts new. Haven't tried, might not work.

Just noticed that the fuel  pressure even with the new pump is 3 psi when the former one when installed Brand new measured 4.2 psi. Something must  be limiting the fuel pressure even though you argue that 3 psi is enough. Another thing i have noticed is that the engine does crank at 2.5 turns clockwise but  will not hold it for many seconds if i dont open them to 3 turns clockwise on both. I thought that if the engine does not keep up to 2.5 turns without the choke on, something is wrong.  

Edited February 24, 2018 by jalexquijano

[Patcon]

57 minutes ago, jalexquijano said:

Just noticed that the fuel  pressure even with the new pump is 3 psi when the former one when installed Brand new measured 4.2 psi. Something must  be limiting the fuel pressure even though you argue that 3 psi is enough. Another thing i have noticed is that the engine does crank at 2.5 turns clockwise but  will not hold it for many seconds if i dont open them to 3 turns clockwise on both. I thought that if the engine does not keep up to 2.5 turns without the choke on, something is wrong

I do not understand why you obsess over this fuel pressure. IT IS NOT THE ISSUE! I have been working on cars for close to 40 years. The issue is in the carb tuning somewhere

[Jarvo2]

I think it’s the hot cam along with the Datsun parts LLC engine!!


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[Captain Obvious]

@Bruce Palmer 

What is your recommended process for dealing with needle alignment on the three screw 72 carbs when the alignment cones have been sheared off? Is that addressed in your instructions or your video? I thought I had seen some documentation about how to handle this in the past, but I can't put my fingers on it.

I mean, I know what I would do, but for someone who doesn't understand the issue... What do you guys recommend?

[Bruce Palmer]

43 minutes ago, Captain Obvious said:

@Bruce Palmer 

What is your recommended process for dealing with needle alignment on the three screw 72 carbs when the alignment cones have been sheared off? Is that addressed in your instructions or your video? I thought I had seen some documentation about how to handle this in the past, but I can't put my fingers on it.

I mean, I know what I would do, but for someone who doesn't understand the issue... What do you guys recommend?

With the piston in and dome in place start running the screws down unformly while lifting the piston with a finger and allowing it to drop. If you are cattywompis and the needle is binding, back the screws off a smidge and nurse the dome sideways until it  (the needle) drops freely. Continue until screws are tight and the needle drops cleanly into the orifice...... Do not under penalty of death, adjust your floats during this operation...... Now that's funny I don't care who you are!!

[Captain Obvious]

51 minutes ago, Bruce Palmer said:

With the piston in and dome in place start running the screws down unformly while lifting the piston with a finger and allowing it to drop. If you are cattywompis and the needle is binding, back the screws off a smidge and nurse the dome sideways until it  (the needle) drops freely. Continue until screws are tight and the needle drops cleanly into the orifice...... Do not under penalty of death, adjust your floats during this operation...... Now that's funny I don't care who you are!!

I'm not sure how well that procedure would translate to other languages, or how much sense it would make to someone who's native language is not English.

You might be about to find out...