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Float level advice, please.


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Posted (edited)

I got the ones that were the same lengths from ztherapy. They're on the car with 2 rear lids, short arms.

Here's the OE front. Looks to be a little more than .806? Could be an eyelash fell on there.

20210418_093230.jpg

Edited by siteunseen
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7 minutes ago, Captain Obvious said:

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

Here's some aftermarket needle type.

20210418_093942.jpg

 

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@Terrapin Z, @siteunseen

When you guys get a chance, could I trouble you both to take a caliper measurement of the short valve going all the way to the top of the valve?

Also, do your short valves have the "R" stamped on them? Looks that way in the pics, but just checking.

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59 minutes ago, Captain Obvious said:

 

@Terrapin Z, @siteunseen

When you guys get a chance, could I trouble you both to take a caliper measurement of the short valve going all the way to the top of the valve?

Also, do your short valves have the "R" stamped on them? Looks that way in the pics, but just checking.

👌

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Terp, Awesome. Thanks for the great pics. And your number matches the Hitachi valves I have here.

So assuming site's 72R valve comes in at the same dimension as what's in your pic, here's a summary of what I have so far. Most of this is old news, but just to put it into a form that my little brain understands...

The float valve for the 72F should be 20.5mm. That is 2mm longer than the previous years and Datsun adjusted both the length of the float ears and the depth of the valve recess of the 72F lid to accommodate that change. The intent seems to be "They wanted the front carb float level to be approx 2mm lower than it used to be in previous years."

The float valve for the 72R should be 18.5mm, and it's interesting to note that this is the same length valve Datsun used on the previous round tops in 70 and 71, but a different part number*. And again, Datsun adjusted both the lengths of the float ears of the 72 R lid as well as the depth of the valve recess to change the float level. The intent seems to be "They wanted the rear carb float level to be approx 2mm higher than it used to be".

*An interesting side conversation would be... So if the float valve for 72R was the same length as the previous years, why did Datsun bother to change the part number? Why not just spec the 70-71 valve for use in the 72R lid? I've got two theories about that:

First is that there's a note in the EF section of the 72 FSM about how they changed from a hardened steel tip to a rubber tip for the sealing of the float valve. Second is that I've got (what I believe are) early 70 valves here and they have a different through hole. The 70 valves I have 2.0mm through hole, while the later 72 valves have a 1.7mm through hole.

So while the length may be the same, they may have sprung for a new part number because of those changes. However, despite those changes, it seems to me you could use the same valve for the 70-71 round tops and the 72R. The 72F is still the outlier.

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7 hours ago, siteunseen said:

Here's mine.

18.5mm and has an "R" on it.  Perfect. You guys are the best!!  @siteunseen  @Terrapin Z

My rebuild kits should be here in a couple days. I sure hope one of them is the long version. I really don't want to have to carve a new one myself.     LOL

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