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Float level advice, please.


siteunseen

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4 hours ago, Blue said:

 If you are in a Hurricane chasing an ME-109E, you can't push the negative Gs to give chase because the floats lift and shut off the fuel.

   Could Cliff be correct? Oh Boy, More discussion. As I understand it, the Miss Shilling's (Tilly's) Orifice was a restrictor orifice in the fuel system that restricted the total amount of fuel the carb. could deliver to match the maximum amount the engine could use and no more. Thus preventing flooding at negative Gs. At least that was the way my Dad explained it to me. WW II, Army Air Corps, Biak Island, South Pacific. The pilots, back then, would roll the plane over when going into a dive to temporarily counter the effects of the negative Gs. Although they couldn't sustain the dive. You see WW II fighters doing that rollover-dive maneuver in the movies and documentaries.

 

 

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  • 1 year later...
On ‎08‎/‎14‎/‎2016 at 6:26 AM, jonathanrussell said:

Attached is a scan of TS73-10.

 

TechnicalSupportBulletin-TS73-10.PDF

Where do you got this?? I  have been looking for this measures for a long time. I tried getting the gap with a 9/16 inch drill bit and a digital caliper and have not been successful in the contrary to others.  My floats are still too lean. I think everyone has a different method.

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Others can fill in the gaps if I get details wrong but every year Datsun / Nissan published a Technical Service Bulletin book for dealership service departments. Each book contains multiple bulletins or instructions on various topics where the factory service manual needed correction or elaboration or explanation based on new knowledge once models were out and being driven. Each yearly book covers all Datsun / Nissan models....in other words is not exclusive to the zcar models. Each book may contain bulletins pertaining to current or recent prior model years. So, the 1974 TSB book may have bulletins that pertain to 240z cars. You can find the TSB books from time to time on Ebay. I have collected pretty much all of them through about 1984. I find them to be really informative. The TSB I cited above is from the 1973 book. For 240z owners, if I were to only own one TSB book it would be the 1973 book. 

Here is an example of a TSB book on ebay.

1978 TSB book 

Regarding adjusting floats....personally I think it is the most important and tedious step in getting the carbs working right. Bending the little tabs one way and then the other in an effort to get the float set just right is insanely frustrating but worth the effort. My personal preference for setting the floats is to remove the bowls, turn down the mixture screws 10 turns, and set the fuel level so that the convex meniscus fuel bubble sits perfectly even with the top of the nozzle. Once you get this accomplished, in my experience, you are able to freely adjust the mixture down to 2.5 turns and then detail adjust using Color Tune or similar. This technique has been documented multiple times on this site and others, fyi.

 

Edited by jonathanrussell
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  • 3 years later...

The 1972 round tops (3-screw) used different float needle valves in the front an rear carbs. Does anyone have the length measurements for the original long and short 72 needle valves?

Here's a pic for (what I believe are) the earlier 70-71 round tops. The length of the valve (just the valve without the sealing washer) is 18.5mm (0.729 in😞
P1190058.JPG

After all that I've read, it is my belief that the two 72 valves should be on either side of the valve measured above. In other words, I'm thinking the front valve should be longer than 18.5mm and the rear should be shorter than 18.5mm. But without having the parts here, that's speculation.

So anyone have some original 72 long and short ear valves handy they could measure. Or anyone have any old ones they replaced before that they would send me to poke around with?

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Here's some I have handy. The first are OE Nissan. The 2nd ones are aftermarket. The pins are different. It's in inches, I'll let you convert to millimeters. Doing yardwork and on a beer break. Front Nissan...

20210417_133132.jpg

rear Nissan...

20210417_133304.jpg

Front aftermarket...

20210417_133512.jpg

Rear aftermarket...

20210417_133552.jpg

I can do bettet later on. I'm covered in weed. LOL

 

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20 minutes ago, siteunseen said:

I had a graft on my eye lid after a welding accident. He got the pliable skin off my penis and it all worked out perfect. He did say I may be a little c o c k eyed temporarily.

What happens when you rub your eye?😂 Do you go bug eye?

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18 hours ago, Terrapin Z said:

Short one in the front carb, tall one in the rear. 

I measured just the hex portion without the sealing washer.  (Is your measurement up on the round part near the top of the valve?)

Thanks guys for the float valve measurements. I did measure from the base all the way to the top of the valve. I figured overall length was the important parameter. I would assume that the dimension from the end of the hex to the top of the valve would be pretty consistent within the same manufacturer, so I ought to be able to convert your measurements to overall.

I wouldn't complain, however, if one of you guys would measure the length from the bottom of the hex to the rounded top of the body. Just don't catch the little retainer spring under the caliper jaw. Easy peasy.

Also, I found a stock long valve here. It's cracked (so it's unusable), but I will check that one too.

Thanks!

Edited by Captain Obvious
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You want base to the top of the circle? I can get that in the morning. I have 3 different sets to show. 2 have "1.7" stamped on them. The Grose valves do not.

I went from the base to the top of the hex, making sure not to get the spring's wire on the one's I posted. Sadurday night baby, my eyes are bad at the moment. LOL

Screenshot_20210417-212835_Samsung Internet.jpg

 

 

Edited by siteunseen
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Yeah, I'm measuring including the rounded top portion. Essentially I'm interested in "how far does the valve stick out of the bowl lid", and that includes more than just the hex portion.

So I'm measuring everything from the sealing washer surface to the top of the valve (not including the movable internal bits). Like this:
P1190060.JPG

 

So this is my (cracked body) 72F valve. I get .806 (20.5mm), That makes sense since the TSB mentioned earlier says they lowered the bowl level for the 72 front carb by 2mm. Both the valve and the bowl lid ears got 2mm longer for the 72F, so all the numbers line up to support that:
P1190059.JPG

So when your eyes get back into focus, let me know.  LOL 

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Oh, and it's clear to me that Datsun really messed around with stuff in 72. The float valves are unique, the lids are unique, everything is different than the previous years. It looks to me like they were chasing minutia. Some engineer realized the slight geometry differences between front and back carb bowls when they mounted on the car and convinced management he could make it better. I'm thinking they should have just left well enough alone.

Also makes it clear why I was having a hard time getting these carbs right... They're all kinds of wrong inside from previous owners.    :excl:

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28 minutes ago, Captain Obvious said:

Yeah, I'm measuring including the rounded top portion. Essentially I'm interested in "how far does the valve stick out of the bowl lid", and that includes more than just the hex portion.

So I'm measuring everything from the sealing washer surface to the top of the valve (not including the movable internal bits). Like this:
P1190060.JPG

 

So this is my (cracked body) 72F valve. I get .806 (20.5mm), That makes sense since the TSB mentioned earlier says they lowered the bowl level for the 72 front carb by 2mm. Both the valve and the bowl lid ears got 2mm longer for the 72F, so all the numbers line up to support that:
P1190059.JPG

So when your eyes get back into focus, let me know.  LOL 

.806" Exactly what I have. I'll get a picture in a couple of cups.

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28 minutes ago, Captain Obvious said:

Oh, and it's clear to me that Datsun really messed around with stuff in 72. The float valves are unique, the lids are unique, everything is different than the previous years. It looks to me like they were chasing minutia. Some engineer realized the slight geometry differences between front and back carb bowls when they mounted on the car and convinced management he could make it better. I'm thinking they should have just left well enough alone.

Also makes it clear why I was having a hard time getting these carbs right... They're all kinds of wrong inside from previous owners.    :excl:

The thing for me was the newer valves you get today are the same length, front and rear. They said to use the washers to make up the difference. I never could get it right so I took the rear off another set and now have two rear lids. I went back to "they should have just left well enough alone".

Also I think the DVD shows how to set the height using the Grose valve but you can't do that with the newer style "needle valves". I wish they would add a sheet of paper in the rebuild kit explaing that. It took me a year to figure it out.

Edited by siteunseen
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Well I guess I'm going to test that statement about the new aftermarket valves being the same front and rear. I just put in an order on rockauto for rebuild kits for the 72. They call out two different part numbers for the kits and make it clear there is a different one for front and rear. So I'm going to soon see why they spec different kits for 72 F and R.

If it's not the needle valve length, then I don't know what it's gonna be. I guess I'll let you know in a little while when the kits get here!  LOL

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