1972 Float Adjustment ...

[David F]

So, all this talk about fuel level made me go recheck mine.  Especially since I set the rear carb the same as the front using the clear tube method.  Removing the pistons and looking at the top of the fuel relative to top of nozzle, the front was perfect and the rear was way low.  So, working on the rear, I set the float so that it was about 1/8” from hitting the cover when inverted.  Rechecked fuel level and still not even close (ie 1/16” from top of nozzle).  Turns out the tang needed to be bent so that float hit top of lid, when inverted.  But, this is okay as fuel shut off occurs prior to float hitting lid.  Now all is good, both fuel levels set to 1/16” down on 2.5 turns.  Fine tune required leaning front and enriching rear...no more than .5 turns for each.  I am hoping cold start is vastly improved.  

2/26/18 update:  Cold start is vastly improved.  But, I will need to wait until the temps are in the 30's to know for sure.  Also, engine "bucking" when cold and under load has been eliminated.  Rear carb was WAY too lean...explains alot.

Edited February 26, 2018 by David F

[Mark Maras]

Thank you David F. @jalexquijano This what I've been trying to explain. It works.

[Stanley]

3 hours ago, jalexquijano said:

Are these fuel levels on the front and rear carb floats okay

Can't verify the fuel level like that. You need to pull the tubes 2 or 3 inches more through the wire clips that hold them in place, so you have more slack. Then you can hold them right against the side of the bowl and make a horizontal line on the bowl with a pencil, right in line with the gas in the tube. Then get your micrometer and measure from the bottom of the lid to the line you drew. Write down the millimeters and then do the other one. 25 mm front / 21 mm rear down from the lid is correct.

I also want to check mine with the nozzle method. My car is raked up in the front since I removed the smog pump and swapped the stock brass radiator for an aluminum one. Beat-up stock bumper is also replaced with carbon fiber one. I did some measurements and calculations to get the front/rear carb  fuel level difference correct with the sightglasses, considering the "gasser" rake and the slope of the parking spot, but I think using the nozzle method with the car on a level spot in the parking lot will give better result.

Nice thing about the sightglasses though, you can leave them hooked up temporarily while idling or driving the car, so you can check that the valves are opening and closing correctly.

[jalexquijano]

1 hour ago, Stanley said:

Can't verify the fuel level like that. You need to pull the tubes 2 or 3 inches more through the wire clips that hold them in place, so you have more slack. Then you can hold them right against the side of the bowl and make a horizontal line on the bowl with a pencil, right in line with the gas in the tube. Then get your micrometer and measure from the bottom of the lid to the line you drew. Write down the millimeters and then do the other one. 25 mm front / 21 mm rear down from the lid is correct.

I also want to check mine with the nozzle method. My car is raked up in the front since I removed the smog pump and swapped the stock brass radiator for an aluminum one. Beat-up stock bumper is also replaced with carbon fiber one. I did some measurements and calculations to get the front/rear carb  fuel level difference correct with the sightglasses, considering the "gasser" rake and the slope of the parking spot, but I think using the nozzle method with the car on a level spot in the parking lot will give better result.

Nice thing about the sightglasses though, you can leave them hooked up temporarily while idling or driving the car, so you can check that the valves are opening and closing correctly.

23  /21 mm from the bottom of the float lid?

[jonathanrussell]

Many of the methods discussed will get a car running fairly well but in my opinion, the 10 turn method described in multiple posts by @DaveR is your best path to success. There are other factors too, getting the needle aligned, getting the pistons dropping with the right amount of dampening fluid, synchronizing, reading plugs or colortune, etc, etc. But, in my experience there is no better way to get the floats adjusted right than the way DaveR explained....quite well. It is still tedious. You have to turn over the engine, watch the top of the nozzle hole at 10 turns down, pull the float caps, bend and shape the tabs....over and over. The difference though in the 10 turn method and the methods that require you to measure the float height in relation to the float lid or the distance the fuel settles in a clear tube (of which there are differing opinions on what the real measurement is) is accuracy. Once you get the fuel level to settle at the top (but not over) of the nozzle hole at 10 turns down, you are perfect.

My 2 cents....

J

[jalexquijano]

Can you describe the 10 turns clockwise method precisely? I guess i will need to go through this method in order to get the 23 mm level or wouldnt it be the same if i open both float lids and dip in a caliper to determine how much fuel is in each bowl without cranking the engine then i will know how much i have to bend the tang.

Edited February 26, 2018 by jalexquijano

[Stanley]

16 hours ago, jalexquijano said:

23  /21 mm from the bottom of the float lid?

No, 25 mm down, front, and 21 mm down rear. There's supposed to be 4 mm difference between the front and rear. I'm not making it up. It's in the Nissan tech bulletin that I posted couple of days ago. The measurements in the bulletin refer to dimension from bottom of lid to top of float but if you do the math (addition/subtraction) you come up with 25/21. Jonathan Russell posted the bulletin originally on the parallel thread. Suggested reading if you're setting the floats.

(25+21) / 2=23 mm so the corrected numbers in the bulletin average up to 23 mm. Did you measure the fuel levels like I suggested? It's super easy. What numbers did you get ?

7 hours ago, jalexquijano said:

wouldnt it be the same if i open both float lids and dip in a caliper to determine how much fuel is in each bowl without cranking the engine then i will know how much i have to bend the tang.

Good Idea if you can remove the lids without letting some gas out, which isn't easy. Also, the float will displace some gas though so you'd need to mic it twice, once with the float in place and once with it removed to measure the difference. Suppose the difference is 2 mm (don't go by that - measure the difference !). Then the target would be 27 mm front and 23 mm rear. Don't get any gas on those plastic calipers, take the measurement with the other end.  When you're done, at least check it with the nozzle method.

 

Edited February 26, 2018 by Stanley

[jalexquijano]

Plug 5 (rear carb) and plugs 2 and 3 (front carb). Idle mixture knobs both at 4 turns clockwise. Car gets stuck on 4 to 5k rpm. Needs more fuel at high rpm. Maybe wrong  float adjustment.

[David F]

Looks lean.  If fuel level was set correctly,  I don't think you would need to be 4 turns down (I don't like clockwise or counter clockwise as it is specific to point of view).  To me, clockwise is up or lean, but I think you mean clockwise as down/rich.

So, have you removed the pistons and verified fuel is 1/16" down from top of nozzle at 2.5 turns down/out/rich?  If not, why not?  From there, fine tuning should get you darn near perfect with one turn of nozzle adjustment in either direction.

Edited February 28, 2018 by David F

[jalexquijano]

Ill try again.

Question any way of gluing the cork gaskets to the float lids? Shall i use RTV silicone or else???

[Mark Maras]

  Cliff (Siteunseen) recommends RTV. It will work just fine. Keep adjusting to get that 1/16". I predict that you're going to be so quick and so good at adjusting floats that you'll be the one giving advice in the future.

[jalexquijano]

Mark,

You are the best! Thanks for your patience! I know some people hate me for opening too much threads but every issue of these cars must be solved logically!