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Ruler to measure and set gap between the lid and bottom of the float on 3 screws su carbs


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#1 jalexquijano

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Posted 12 February 2018 - 06:23 AM

After watching the just su dvd produced by ztherapy i was wondering where can i get a ruler to neasure the 9/16 or .55 mm gap needed for the floats. How would you get a precise measurement?

#2 thisismatt

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Posted 12 February 2018 - 06:30 AM

9/16" is nowhere near .55mm. I'm not familiar with SUs to know what exactly you're referring to or how accessable, but if it's small like .55mm then use feeler gauges.
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#3 ]2eDeYe

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Posted 12 February 2018 - 06:48 AM

I don't know much about SUs, but....

This link states that you should use a test bar. This is basically a block that is at the dimension you need, similar to the feeler gauges Matt mentioned but those are super thin. 

 

http://sucarb.co.uk/...ng-float-height

 

I don't see 9/16 or a metric measurement there though, you may want to verify exactly which SUs you are running before making adjustments. It may be a better idea still to pick up a factory service manual for your car. 


PS
.55mm is .0216"
9/16" is about 14mm 


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#4 Crashtd420

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Posted 12 February 2018 - 07:17 AM

After watching the just su dvd produced by ztherapy i was wondering where can i get a ruler to neasure the 9/16 or .55 mm gap needed for the floats. How would you get a precise measurement?


I don't know much about su carbs... but from the info redeye posted it sounds like you use a pin with the correct diameter...
With that said you can use a drill with the correct diameter...

#5 Doctor510

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Posted 12 February 2018 - 07:33 AM

Check out a product called Float Synch.  I have used a 14mm rod slipped under the float arm curve with the cover upside down.



#6 datzenmike

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Posted 12 February 2018 - 08:46 AM

The float level setting is rather arbitrary as higher than recommended fuel pump pressure can force it's way in and raise the fuel level in the bowl. The setting may be correct, but the unseen fuel level inside is not. A better way is to set the actual fuel level by using a clear plastic hose set into the drain plug hole at the base of the float chamber and held up beside it. The clear vinyl hose must be taller than the float chamber. Fuel will flow out and up the tube and can be perfectly measured down from the float chamber gasket on top to get 22 or 23mm setting. Or what ever the manual says.

 

SUs and most carbs react much differently when the fuel level is wrong. Most Datsun carbs have a window in the front so you can actually see the fuel level. This visual much more reliable than simply measuring and setting the float drop. I've never seen a 340 Hitachi that had perfect fuel level no matter how accurate the float drop was set. They always can be tweaked.


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#7 Doctor510

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Posted 12 February 2018 - 10:08 AM

After watching the just su dvd produced by ztherapy i was wondering where can i get a ruler to neasure the 9/16 or .55 mm gap needed for the floats. How would you get a precise measurement?

Try .55" not .55mm



#8 Stoffregen Motorsports

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Posted 12 February 2018 - 10:15 AM

Again with the metric crap...!



#9 datzenmike

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Posted 12 February 2018 - 10:32 AM

I grew up with Imperial measure but am so converted to metric that now when someone says 100' I have to convert to metric for it to really mean anything. Thirty meters? Oh hell yeah that's about 1/3 of a football field length. About twice the length of a semi trailer, 3 times the height of a telephone pole and 1/3 the height of the Statue Of Liberty...... easy.

 

Good luck converting 5/32" to decimal without a chart.


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#10 Dolomite

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Posted 12 February 2018 - 01:57 PM

I use a length of clear fuel line and run it above the top of the bowl so it won’t spill fuel. Measure from the mounting surface of the top of the bowl to the fuel in the line. It should be anywhere from 19-23mm depending on your fuel needs at wot. Make sure both carbs measure the same and bobs your uncle.

Edit: shite, didn’t notice mikes post.
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#11 jalexquijano

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Posted 12 February 2018 - 02:14 PM

Sorry its .55 inches which should be 12mm.

#12 datzenmike

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Posted 12 February 2018 - 02:20 PM

I use a length of clear fuel line and run it above the top of the bowl so it won’t spill fuel. Measure from the mounting surface of the top of the bowl to the fuel in the line. It should be anywhere from 19-23mm depending on your fuel needs at wot. Make sure both carbs measure the same and bobs your uncle.

Edit: shite, didn’t notice mikes post.


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#13 distributorguy

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Posted 13 February 2018 - 05:23 AM

Use a drill bit.  



#14 jalexquijano

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Posted 18 February 2018 - 07:38 AM

9/16 drill bit with or without pressing the needle valve pin that shuts the fuel?

#15 Doctor510

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Posted 18 February 2018 - 08:34 AM

Sorry its .55 inches which should be 12mm.

Actually it's 14mm.



#16 jalexquijano

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Posted 19 February 2018 - 04:38 PM

.55 inch with or without pressing the needle valve stem? still not clear!!!



#17 Doctor510

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Posted 19 February 2018 - 06:31 PM

.55 inch with or without pressing the needle valve stem? still not clear!!!

Without!



#18 datzenmike

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Posted 19 February 2018 - 07:06 PM

I use a length of clear fuel line and run it above the top of the bowl so it won’t spill fuel. Measure from the mounting surface of the top of the bowl to the fuel in the line. It should be anywhere from 19-23mm depending on your fuel needs at wot. Make sure both carbs measure the same and bobs your uncle.

Edit: shite, didn’t notice mikes post.

 

This eliminates all the guess work. Set the fuel level not the float. 


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#19 jalexquijano

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Posted 21 February 2018 - 01:50 PM

19-23mm measured from where?