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SU Float Level - set up

Started by _Agent 34_ , Oct 29 2014 05:10 AM

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10 replies to this topic

#1 _Agent 34_

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Posted 29 October 2014 - 05:10 AM

Guys,

can any one EXPERIENCED let me know the following;

a) the upside down measurement of the float off the cap - eg there is a measurement off the float to the cast cap

is there a difference in settings for race cars as opposed to road going cars

Last hit out had a small fuel starvation " intermittent stutter " at higher revs which sort of got worse as the day went on, so I have stated to pull the SU's apart last night for a general clean and check. the tabs on the floats seem to have been bent a few times.

G

Edited by Agent 34, 29 October 2014 - 05:12 AM.

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#2 warrenm

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Posted 29 October 2014 - 05:45 AM

1 3/4" or 2"?

What fuel pressure?

What type of needle & seat are you using? I find that the inlet needles with the ball end, which flow more fuel past & seal better if your using a higher pressure.

HS carbs with the early nylon float and steel needle. The gap between the lever and the face of the lid should be between 0.125" and 0.187".

HS carbs with the later all nylon float and delrin type needle. The gap between the float and the lid face should be between 0.062" and 0.187" with the float resting on the needle but not depressing it. This type is non adjustable.

Edited by warrenm, 29 October 2014 - 05:53 AM.

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#3 hanra

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Posted 29 October 2014 - 06:48 AM

This what I use with the twin HS2s on my red car.

39C7D731-8CB7-435A-B0D4-82685480CF1F_zps

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#4 _Agent 34_

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Posted 29 October 2014 - 07:27 PM

1 3/4" or 2"?

What fuel pressure?

What type of needle & seat are you using? I find that the inlet needles with the ball end, which flow more fuel past & seal better if your using a higher pressure.

HS carbs with the early nylon float and steel needle. The gap between the lever and the face of the lid should be between 0.125" and 0.187".

HS carbs with the later all nylon float and delrin type needle. The gap between the float and the lid face should be between 0.062" and 0.187" with the float resting on the needle but not depressing it. This type is non adjustable.

Warren,

running what seems to be a standard vk fuel pump - so pretty sure it's a 4psi standard one.
the carbies are 1 3/4
no fuel regulator
off fuel block
Ball end inlet needles
doesn't flood - which amazed me from what have heard about running a regulator

i will have to post a photo tomorrow of the float and also the carby as i am unsure which type i have.

thanks for the info guys on these. there a pretty simple set up.

I'm pulling them apart one by one and cleaning them and want to set the float level and needle height prior to going back in. although i will check prior to touching

how many flats (turns ) down on the main Jet would be a standard.starting point.?

I just need to make them the same turns down and will set with the verniers for a start. Interested to know what this base measurement is.

thanks g

Edited by Agent 34, 29 October 2014 - 07:28 PM.

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#5 hanra

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Posted 29 October 2014 - 07:37 PM

As a starting point. Wind the jet all the way up, then back it out 12 flats or two full turns. That's where I start with my HS2s.

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#6 SA EH

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Posted 29 October 2014 - 09:15 PM

And as a guide, the jets in mine ended up being 1.6mm down from flat at the top. This does depend on the main needle size though.

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#7 warrenm

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Posted 29 October 2014 - 11:11 PM

I generally set 1 3/4" at .050" down from the bridge with verniers as the starting point.

I can set my fuel pressure at 6psi(not that I use 6psi) without flooding with the high flow Grose ball inlet valves & was flat out getting 4psi with the std type.

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#8 _Agent 34_

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Posted 30 October 2014 - 05:45 AM

thanks for that.

I'll tell you the problem.

As we started the day at the track times were running around the 1.19- 20ies as the three days when on the laps times came down to a consistent 1.16.

the motor started to stumble once it had come out of the left and then onto the back straight at wakefield - like a electronic points that looses battery amps it only happened in higher 5ish to 6 thou rpm

it only seemed to be a " left hand corner issue" and when it started didn't happen on any other part of the track

then it started to happen down the main straight again once it hit the above rpm.

we checked the battery and it's charging.

My next step was to clean the carbies and check the float levels and see if there was any shit in the carbies.

seeing that I'm pushing the car harder and it's only a 4 psi pump and i have the " ball type" needle - could this be a fuel pressure issue ?

I'll check the float level tonight.

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#9 warrenm

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Posted 30 October 2014 - 06:11 AM

4psi is plenty. Have you got a pic of the carbs on the car? Was there plenty of fuel in the tank, it maybe uncovering the pickup in the turns.

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#10 _Agent 34_

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Posted 31 October 2014 - 05:48 AM

So tried the set up and measured the distances. It seems like my float has a bend in the metal part which is not as per Brad's photos. It seems to have a " z" bend in the shaft and need to know if this is correct or has been butchered.

i have looked on Su midel and they only sell a a float with a " flat bar" .

If anyone can give some clarity after looking at the photo will save a trip to Su Midel - if the floats have been bent then i will need to get new floats.

One of the photos i have a 1/8 drill bit under the float.

Also can anyone identify this fuel pump - I assume that it's just a standard type - while I'm at it will get a pump kit and rebuild.

the first photo in the garden is showing the float level as pulled out. the other ones are generally after the " arm is adjusted to give a closer 1/8th gap"

thanks

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#11 warrenm

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Posted 31 October 2014 - 10:23 PM

Take the inlet valves out(needle & seat) & check what size washer is under it, as you can adjust the float level by fitting a thicker or thinner washer.