Jump to content
jalexquijano

Setting Correct Float Level On 3 Screws Su Carbs For 1972 240Z

Recommended Posts

How do you set the .55 inches 9/16 measurement on the front and rear 3 screws su carb floats? Do you use a set of calipers? I need to know if the measurement is taken from the rim of the lid to the base of the float depressed or unpressed?

Share this post


Link to post
Share on other sites

It's all described in the workshop manual.

Share this post


Link to post
Share on other sites

It's all described in the workshop manual.

 

I watched the Ztherapy Just SU DVD and its not clear. I also reviewed the Haynes Manual and its not even explained precisely.

Share this post


Link to post
Share on other sites

I would like to know if the .55 inch gap must be measured between the float valve lid bottom to the float valve as shown without depressing the pin on the needle valve. The video you uploaded deals with grose jets not neddle valves. Its really difficult to set the floats level this way.

post-106003-0-87161000-1518877340_thumb.jpg

Share this post


Link to post
Share on other sites

Set it exactly like in Gav's 1st video from around the 26 minute mark. Set it with the lid upside down so the valve is closed by the weight of the float, don't use your fingers to push on the float to close the valve, you may push too hard causing the tab on the flaot to bend and get an incorrect reading. Grose jets are no different to needle valve as far as setting float height. Calipers are a bit fiddly to use, grab a 9/16" drill bit and use that, similar to the way the guy in the video uses block of the right thickness.

Edited by 1600dave

Share this post


Link to post
Share on other sites

It is taken with the valve closed by the weight of the float. You need the float to be in that position when the valve closes and shuts off fuel to the float chamber so that it keeps the level of fuel in the float chamber correct. 

 

To open another can of worms, to get it 100% perfect, you can ignore all that 9/16  float height setting stuff and set it by measuring the level of fuel in the jet, although I don't know what that setting is for 3 screw Hitachi SU's.  :-X

Share this post


Link to post
Share on other sites

Im posting some pictures to obtain your clarification if the 0.55 inch gap is taken from the bottom of the lid to the pin of the neddle valve not pressed by the weight of the float.

Share this post


Link to post
Share on other sites

Im posting some pictures to obtain your clarification if the 0.55 inch gap is taken from the bottom of the lid to the pin of the neddle valve not pressed by the weight of the float.

post-106003-0-20232300-1518965118_thumb.jpg

post-106003-0-82106900-1518965209_thumb.jpg

Share this post


Link to post
Share on other sites

Set it exactly like in Gav's 1st video from around the 26 minute mark.

 

 

It is taken with the valve closed by the weight of the float. You need the float to be in that position when the valve closes and shuts off fuel to the float chamber so that it keeps the level of fuel in the float chamber correct. 

Share this post


Link to post
Share on other sites

Like this???? I installed the longer needle and seat that goes on the 3 screws front carb float bowl and set the idle mixture screw to 2.5 turns clockwise. What next? Do i measure the fuel height with the pair of clear tubes connected to the drain plugs?

post-106003-0-79535700-1519234222_thumb.jpg

post-106003-0-41145300-1519234267_thumb.jpg

post-106003-0-93625000-1519234301_thumb.jpg

Share this post


Link to post
Share on other sites

That's all you need to do, if you've set the float to correct height you're done. I can't vouch for specific settings for 3 screw carbs, never played with them.You did take the gasket off the float chamber lid to set float height ?

 

Connecting clear tube to drain plugs isn't required assuming setting float height is done correctly.

Share this post


Link to post
Share on other sites

2 Questions:

 

1. Does the float needs to be parallel to the float lid when measuring the .55 inch gap or can it be bent or incline downward?

 

2. Is the measurement taken from the base of the lid to the bottom of the float or from the edge or rim or the float?

Share this post


Link to post
Share on other sites

2 Questions:

 

1. Does the float needs to be parallel to the float lid when measuring the .55 inch gap or can it be bent or incline downward?

 

2. Is the measurement taken from the base of the lid to the bottom of the float or from the edge or rim or the float?

 

I think you're over thinking it.

Share this post


Link to post
Share on other sites
Posted (edited)

1. Nope, doesn't have to be parallel. Measure to roughly the centre of the float / across centre of float chamber lid, ie try to "average" it.

 

2. Usually gasket surface of lid to bottom (well, top...) of float. I haven't seen a 3 screw float up close and personal to be 100% sure of shape, but that's how you do it on British SU's.

 

Really, you're talking a millimeter or two difference for the various methods of measuring you've suggested. Get it close enough and it will be fine, like the pic beow (ignore the fact that its a pommy carb, different float, different way to adjust float height and different sized rod used to set height).

post-100293-0-80552800-1519875429_thumb.jpg

Edited by 1600dave

Share this post


Link to post
Share on other sites

1. Nope, doesn't have to be parallel. Measure to roughly the centre of the float / across centre of float chamber lid, ie try to "average" it.

 

2. Usually gasket surface of lid to bottom (well, top...) of float. I haven't seen a 3 screw float up close and personal to be 100% sure of shape, but that's how you do it on British SU's.

 

Really, you're talking a millimeter or two difference for the various methods of measuring you've suggested. Get it close enough and it will be fine, like the pic beow (ignore the fact that its a pommy carb, different float, different way to adjust float height and different sized rod used to set height).

attachicon.gif float.JPG

Okay. So it doesnt matter if the gap is measured with the weight of the float closing the needle stem when the gap is .55 or 9/16 inch? Its really hard to accomplish this measurement blowing through the gas hole to keep the needle pin from depressing. I am using a wooden stick that measures .55 inches.

Share this post


Link to post
Share on other sites
Posted (edited)

Its really hard to accomplish this measurement blowing through the gas hole to keep the needle pin from depressing..

 

Why would you want to do that ? 

Edited by 1600dave

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×