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SU Sightglasses available (see fuel bowl levels)

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After continually fiddling with my SU's I've created a fairly inexpensive Sightglass for my carburetor float bowls. My device will allow me to see what the floats are set at and ensure that the carb gross fuel mixture setting is correct. Then I'm able to dial in the fine mixture setting with the adjustment knobs on the nozzle to get back to factory specs.

Would there be interest from any members in a set (allows you to see levels in both carbs at the same time)? I'd be willing to provide 2 sightglasses with instructions for $15 including shipping anywhere in the US. PM me if you're interested and I can provide more detail.

post-26781-14150824328667_thumb.jpg

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Dave:

Excellent idea. I've made my own, and thought how I'de always wanted to offer the service, but well, you know... Glad you're taking it on. Many will benefit.

One comment. I've been twiddling with several peoples SU's recently, and I've been using the standard 23mm down from the top of the float bowl measurement. I looked at the FSM this Morning to find the nifty picture you attached and noticed something about the reference for the "top" of the 23mm measurement that I didn't realize.

post-12190-14150824328903_thumb.jpg

I seems I've been doing this wrong. I've been measuring down from top of the cover at the gasket, not the internal "roof" as it were as the FSM drawing indicates. I think its only a 1mm or so, but still. Might want to amend your drawing to reflect this too.

I'm going to review a few of the posts about this (there are many) and see what everyone else has been doing.

Jim

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Great point, Jim. I actually just grabbed this pic to illustrate what we were trying to accomplish. I'm still formalizing my instruction manual based on my learnings throughout the years. The funny thing is I was running at about 15mm of fuel and having tons of issues, raising it back up improved the drivability and performance once tuned properly.

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I found the drawing you used, its from Blue, in this post;

http://www.classiczcars.com/forums/su-carb-technical-articles/44010-setting-fuel-level.html #8

Right next to it, he has the FSM drawing I used, showing the top reference at the 'roof' of the cover, but his drawing has it at the gasket....

Now we'll have to convince him to make an amendment to that thread. !! He's never going to let me forget this.... ;)

Now we need a better way to improve the tedious and gasket wasting method of endlessly adjusting float levels...

Edited by zKars

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Now we need a better way to improve the tedious and gasket wasting method of endlessly adjusting float levels...

Sounds like you want a set of OER triples. LOL

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Great idea! I know from experience that getting the float level correct on both carbs is the essential first step to adjusting the mixture in these carbs. I've done this using a clear vinyl tube on the nozzle-tube nipple, but that takes fiddling since you obviously can't check it with the engine running. Can I assume that you are using the drain plug on the bowls? If so, remember that some of the early Series 1 cars came with SUs that had no float drains.

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I created this tool out of necessity since now that gross jets are no longer available, its a pain to accurately set the float level on the bench while rebuilding the carb's.

The approach I took is for the tool to used temporarily while checking float levels; once set, the sightglass is removed. I pull the fuel hose from the float bowl & connect my sightglass to the nipple. Its preformed and graduated to allow the user to easily see how high the fuel level should be. Then a couple cranks of the engine (coil wire unplugged & trans in neutral), the sightglass fills up. Then it becomes a game of opening up the float bowl lid, bending the tang and re-filling the bowls.

Once set the floats should be good for quite a long duration, thus the reason I didn't invest in drain plug bungles. I actually prefer running this test without the engine running.

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I'm interested. I've been fighting with mine and need to redo them very soon.

BTW, is there a better way to deal with the bowl gaskets? They work great the first time and then they curl and get hard to line up. Can we glue them to the lids? Is there a better gasket material? I hate these things.

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The approach I took is for the tool to used temporarily while checking float levels; once set, the sightglass is removed. I pull the fuel hose from the float bowl & connect my sightglass to the nipple. Its preformed and graduated to allow the user to easily see how high the fuel level should be. Then a couple cranks of the engine (coil wire unplugged & trans in neutral), the sightglass fills up. Then it becomes a game of opening up the float bowl lid, bending the tang and re-filling the bowls.
Very good. That's exactly how I did mine, except my tubes weren't calibrated. This will work.

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Dave, Got a silly question about exactly where you connect you site glass. You say you remove the fuel hose from the bowl and connect to the nipple. I'm hoping you mean vent hose. I'de also really like to see a picture of this contraption of yours and how it measures fuel level from the vent line nipple. I can see a probe that touches the top of the float to give you an indication, but that's not the top of the fuel level. Please help the eternally confused. Thanks

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Here is my tool:

I tee'd 3 clear hoses, two of these carry fuel the normal path from the bottom of the fuel bowl to the bottom of the jet.

The third "fuel level" hose is open at one end and rises up from the "T".

I have a 23mm (or other LOL) mark on the outer fuel bowl wall and hold the "fuel level" hose against it while cranking with the plugs out.

Once the fuel level in the hose is noted against the 23mm mark, I tip the "fuel level" hose out into a cup and drain a bit more fuel from the fuel bowl then dump the cup into the fuel tank. The float level can then be adjusted at the tang and the level check repeated Ad nauseam until correct.

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Thanks to gravity and atmospheric pressure, water (and other fluids including gas) seeks its own level. What this means is if you take a tube and hold it in a “U” shape and fill it partially with water, no matter how high you hold one end of the tube, the water will be the same height on both sides. This is the basic function of the sight glass. The level of gas shown in the sight glass is the same height as the fuel in the float bowl.

My approach is to pull the fuel line from the bottom of the floatbowl.

post-26781-14150824364933_thumb.jpg

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Dave:

Well DUH on me. I get the fluid level in both sides of the U tube part, it was the "just where are you hooking it up" part that eluded me. There are 3 nipples on an SU bowl of course not two, I neglected the one on the bottom as connection point for your site tube. Thanks for the clarification. This does remove the issue with some bowls not having the drain plug. I like it!

Blue, the idea of a permanent site glass right in the side of the bowl! Now that's brilliant! Nice simple 1/4 NPT. The glass center seems to be about 3/8 in diameter, ~ 10 mm which is plenty to see the level. Just make sure it doesn't protrude too far into the bowl and interfere with the float. Install it on the engine side of the bowls or on the ends, so you still have a chance to see the level with the air cleaner in place.

Edited by zKars

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the idea of a permanent site glass right in the side of the bowl! Now that's brilliant!

Yeah, too bad Datsun didn't include one.

Oh wait... They did!! :bandit:

flatcapacity1.jpg

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No! really? You mean there may be a good reason I kept a set of flat tops? They aren't just to hold the bbq cover on in a wind storm?

Cute story. I went to the site Blue posted and tried to buy two site glasses via their online store. $6.62 each. Got to the checkout. Guess how much the shipping quote was ? (CA to Alberta). $102 US..... I was about to throw my hands up and JB weld a scrap piece of clear plexi over a drilled hole when this revelation about site glasses on flat tops comes up. Nothing like OEM parts. Even though I might have JB weld that site glass to a round top fuel bowl :)

Thank's capt'n!

Edited by zKars

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Here's mine, from ztherapy: post-24191-14150824370436_thumb.jpg It works ok but I'm thinking maybe install a permanent one, maybe one of these:McMaster-Carr Happy reading !

Also, I got some new float bowl gaskets and stuck them to the bowl with the blue stuff on the bowl side. They're doing fine and I had to remove the reinstall the lids on both carbs about 10 times to get them more or less right. It would help to have an adjuster screw or something on the tang on the float to make it easier to adjust, but at least once they're set they should stay that way, unless the needle valves get bad or the fuel pressure changes.

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Got to the checkout. Guess how much the shipping quote was ? (CA to Alberta). $102 US.....

Thank's capt'n!

Jim, I'm in the US for a month. I'll pickup a couple of sets and send you one.

Philip

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What carb is that Cap'n?

Haha! Yeah, that's the sight glass from a "boat anchor" flat top. Just one of the many improvements they made to the Cro-Magnon antiquated round top design. (Where's my hornet's nest smiley...?) :) Seems that what's old is new again?

No! really? You mean there may be a good reason I kept a set of flat tops? They aren't just to hold the bbq cover on in a wind storm? Thank's capt'n!

My pleasure JK. I've taken those sight glasses out before. They are real glass (I wouldn't use plexi for gasoline), and are pretty thick. They are sealed by one O-ring that gets squished up against the face of the glass disk when you tighten the screws. Use Buna-N (or Viton if you can find it).

$102 shipping. That's rude. Would you like me to order some of those sight glasses for you and send them to you? The screw in types would probably be easier to mod into the round top bowls than the ones from the flat tops.

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cappy, seems like Mr Phil is getting me some, but thanks for the offer!

After looking at my bbq anchors it wouldn't be simple to adapt those site glasses to the round bowls. Man they went to a lot of work to mount them.

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I saw Phillip's message as soon as I finished mine and saw that he's got you covered. He should be able to hand carry a few of those for you (and him, I suspect). Excellent.

And you're right about adapting the sight glasses from your anchors. They are designed to mount into a large flat surface, which doesn't exist on the round top bowl sides. You got a tig capable of aluminum? :pirate:

But before you pull the trigger on a sight glass... Take a look at the other options at that web site. They offered straight threads as well, and I don't know which would be a better approach. If you're relying on pipe threads to provide both mechanical strength and hydraulic seal, I'd be wary about the small number of threads of engagement that you'll be able to get in the relatively thin wall of the bowl casting. I'm thinking that a straight thread and an O-ring might me a better alternative. Just something to think about.

I've given it some thought in the past as sight glasses into the round tops has been a stalled project on my workbench for years, but never enough deep thought to make chips.

Measure once, cut twice, I always say! LOL

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