Esprit S2 - Fuel level height in carbs

[Billy_Idle]

Hi

Has anyone had any success with setting the fuel level in the carbs to 27mm from the top of the carb body as described here?

http://sideways-technologies.co.uk/forums/index.php?/topic/1048-setting-dhla-dellorto-dellorto-float-fuel-level/

Over the last 3 days I must have adjusted the float level and measured the resulting fuel level over 30 times, but I can't get consistent results. I'm having 2 problems:

1. Results are inconsistent - decreasing the float gap will sometimes increase the fuel level as expected, but sometimes not. Or I'll set the float level then re-check the resulting fuel level 3 times (emptying some fuel then refilling from the fuel pump each time). Maybe twice I'll get the expected result, the third time the level drops 2mm or something.

2. The fuel level seldom gets as high as 27mm (or higher, eg 26). Out of 30+ attempts I've seen the fuel level at 27 or 26 maybe 4 times, the rest have all been 28, 29 or 30, with the vast bulk of adjustments coming out at 28mm. I'm now thinking that 28mm is the max level that the fuel can go regardless of the float level, (which I've set as low as 12mm from the gasket and am still got the 28mm fuel level). I've also tried filling the fuel to the 27mm level with a syringe, then holding in the floats without the lid and pushing them down 15mm - they are clearly trying to push up, which seems to confirm that 27mm is not achievable.

I've noticed my car is fitted with 7g floats rather than 8.5g, but apparently this shouldn't matter.....although maybe that's the problem, and with 8.5g the maximum fuel level would reach 27mm?

Any thoughts very much appreciated!

Thanks 🙂

[DaveyT]

Perfect timing. I will be following closely.

I recently balanced my carbs (DHLA 45s)and started to check the 27mm level, but the problem i noticed was that my carbs dont seem to sit level. (Front to back difference in the fuel level in each bowl)

I was certainly nowhere near the 27mm figure, but can't recall which way now. The car itself is currently on gravel standing, and I cant move it, so it could be that the car itself is not sitting level, so I decide to crack on with other stuff and revisit fuel level when I know its on flat ground.

but in essence, answer to your query, with a static setting of 15mm, the fuel in my carbs does not appear to be colse to 27mm as described above, even if I averaged out the level differences.

[Billy_Idle]

I see your point, mine is the same. I was jacking the car a couple of inches at the back to get it level, but now I think about it that was maybe a mistake.

Here's a quote from the article:

'Its important to do this (measure the level) on the car, as different fitments/manifolds give a different "angle" or rake to the carb, the main-jet stack must be supplied with a proper fuel level.'

I took this to mean that the fuel level must be 27mm at the jet stack regardless of how the carbs are angled. It's the measurement at the stack that is key, regardless of what is happening elsewhere in the bowl. 

But are the jets far enough apart for any front to back difference to be significant? Hrm

[DaveyT]

@Billy_Idle....seems it is possible!

 

[gvy]

Hi,

After I rebuild my carbs,(years ago)  I used this method to set float level. I did not test this a number of times, because the engine was fine.

Some months ago , I retested the float level and all was still OK. So uptill now, for me this method works.

Some remarks.

1. I used viton tips instead of metal tips when I rebuild the carbs.

2. I had trouble in the past with the fuel pump and had to change it for a new one.

3. Make sure there is a free flow of fuel from the pump, so no filters blocked. You can trie that with a glass bowl and deconnect the fuel line at the carbs and let the fuel free running ( fuel pump pumping of course) in the bowl

 

[Billy_Idle]

Thanks very much for the replies.

The problem may be solved! Here's an update.

I made a little wire frame to emulate how the carb lid holds the floats, filled the bowl to 27mm with a syringe and put the floats in the bowl on the wire frame. The floats (7g )sat around 11.5-12mm from top. It looks like to achieve a 27mm fuel level the float gap would need to be set to around 11.5-12mm, which is a long way off the recommended 14.5-15mm. However, I previously tried a 12mm gap several times and got inconsistent fuel levels from 26-28mm, but mostly around 28mm. My conclusion from all this is that setting a reliable fuel level of 27mm may not be possible with 7g floats on a 907 engine. Perhaps this is due to the angle of the carbs? 

I then wrapped some wire evenly across the top of the floats to take their weight to 8.5g. 

Immediately the fuel level started behaving itself. The level could set the level at 27mm, or indeed anywhere through a range of 26-29mm. Any adjustment in the float gap gave the predicted result to the fuel level. The results were identical on both carbs.

And the results are consistent. I set the level to 27mm on the rear carb and let it refill 5 times, with the correct  27mm result each time. Checked 3 times on the front carb as well.

Achieving a 27mm fuel level required a float gap of 14mm (measured from the gasket). http://sideways-technologies.co.uk recommends a gap of 15.5-16mm, the lotus manual recommends a gap of 16.5-17 including the gasket, (which equates to 15.5-16mm from the gasket). So my float setting is 1.5-2mm off the recommended. Not ideal, but acceptable? (especially as my botched up floats may not behave exactly like genuine 8.5g floats)

I think I need to treat myself to some 8.5g floats and some Viton needles too, as suggested.

I haven't tried starting the car yet, I'll update again when I do!



 

[DaveyT]

Genius!

I have viton needles, and mine’s a 912 with 8.5g floats, but your description, reasoning and methodology for setup is impeccable!

this time next week, Rodney!....

[Billy_Idle]

I started the car today - what a difference!

Beforehand,  I had set the float level at around 16.5mm  on the 7g floats and was getting an inconsistent and unreliable fuel level, but maybe around 30mm as far as I could tell. The engine was barely running, and sounded like a sack of hammers - it would reluctantly start, more or less idle without choke, but had to be very gently coaxed up the revs or it would cut out immediately, and was spitting back badly. It would cut out completely after about 5 minutes. I had balanced the carbs as best I could and improved it slightly, but it was terrible, no chance it could be driven.

It's sooooo much better with the 8.5g floats and the 27mm fuel level. It starts very enthusiastically, and revs up no problem. I haven't tuned it yet, but had the vacuum gauges attached anyway so roughly equalised the two carbs.

The car isn't on the road so can't be properly tested. I also suspect compression problems, and haven't even set the ignition timing yet. But the fuel level was definitely at the root of the poor running. It sounds like a runner now - a bit rough, but a runner! 🙂

 

[DaveyT]

Hi Jason, glad to hear it all worked.

just managed to get mine level, and I have the following, so obvs need to make adjustments Averaging 3mm (I also set static float height to 16mm)

I assume your fuel level also sit this wonky in the carbs? So did you set it to an average 27mm, or bias towards the lhs (jet stack). Meantime, Mean average is what I shall aim for

@MikeJ, I would also appreciate your review of performance on this based on yr changes above...

thx, Dave

[jonwat]

15 minutes ago, DaveyT said:

Those carb mounting nuts look over tightened to me, especially the right most one. 

[DaveyT]

Thanks John,

I”ll go back and re-check the spacings....

fuel heights successfully set....😅

[DaveyT]

I’ll start a new thread to ask you for some help John... 

[MikeJ]

Hi Dave, carbs are re-built and re-mounted but haven't yet had time to tune up and try it out. I adjusted the nearside float down a mm to reduce the level to nearer 27mm at the jets. I'm hoping it will solve my right hand cornering problem. cheers Mike

[peteyg]

The carb mounting washers should be tightened to a gap the width of a 2p coin is what I've always been told.

Pete