Lotus Elan

flooding stromberg's

PostPost by: Bits » Sun Jan 22, 2023 5:32 pm

Hi All,
I have stromberg 175 CD 2’s from a Land Rover on my S4 elan and they have the jet/needle adjustment at the bottom of the float.
I/m just completing a restoration of the whole car and have had the engine running and set up the carbs.
They are fed with an electric fuel pump (3-5 psi) and regulated down to 2psi (which I have checked with a gauge which I have let run for several minutes and it has remained at 2psi).
I have refurbed the carbs and set the floats to between 16-17 mm.
If I leave the ignition on the carbs flood and fill the engine cylinders with fuel.
I have checked everything over and over and can't find why the fuel will not shut off.
The floats are not full of fuel.
The fuel shuts off when I have removed the bowl and used my finger to lift the float.
I'm at the end of what I can do - can anyone help please?

Mark.
Last edited by Bits on Mon Jan 30, 2023 10:10 pm, edited 2 times in total.
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PostPost by: Bits » Mon Jan 23, 2023 6:54 pm

I've just found out that the float bowl is required to be vented to the atmosphere.
Does anyone know how this is achieved please.
A blocked vent could be the cause.

WIN_20230115_12_15_06_Pro.jpg and
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PostPost by: SENC » Mon Jan 23, 2023 7:14 pm

Screenshot_20230123_141318_OneDrive.jpg and


I would also wonder about the valves and whether they are correct for the Elan, since the carbs are from an LR. Did you change them for the proper size?
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PostPost by: Bits » Wed Jan 25, 2023 4:28 pm

mine do not have the vent.

WIN_20230125_16_24_27_Pro.jpg and


WIN_20230125_16_44_51_Pro.jpg and


Mine vent to the outside through this hole! which I filled with mastic (now removed) So with it vented to the outside dirt can get into the float bowl.
Is this a very early detail before a further drilling takes it to the air box?
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PostPost by: SENC » Wed Jan 25, 2023 9:48 pm

My carbs are off - when at the shop in the next couple of days I'll take a look and grab some pics if of value. Will also check my book to see if there are any noted differences for the LR version. There were multiple versions of the same 175 CD carbs for different vehicles.
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PostPost by: Bits » Thu Jan 26, 2023 7:17 am

Thanks SENC
A guy I know has a pair on his stag and he helped me set mine up.
I think my carbs are early ones.
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PostPost by: SENC » Thu Jan 26, 2023 5:14 pm

Mine do have the vent - see picture below. I circled series marking on mine - have other carbs where the series marking is on the edge of that flange or the edge of the flange on the other side of the carb (eg, 3322R).

IMG_20230126_120137.jpg and


This picture of one of my carbs from the side does not show the same hole as yours. It looks like there is a brass tube in the same hole on your other carb - somewhere in my memory is lodged an image of that being used, I'll have to look around.

IMG_20230126_115944.jpg and


The following excerpt from a Zenith service bulletin on the 175 CDSE and CD2 (https://zenithcarb.co.uk/zencdsecd2/?___store=zenith) would confirm that ventilation is important...

IMG_20230126_120320.jpg and


I haven't put my hands on my Zenith carbs booklet that identifies components by (many of) the vehicles the carbs were installed on, but will keep looking. In the meantime, can you add what LR yours came from, confirm the model (175CDS, 175CDSE, etc.), and see if you can identify series numbers on both your carbs (may be different)? One note about the model number on the top of the carbs, those tops are somewhat interchangeable so unless you know the history it is also possible they were swapped onto other bodies.
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PostPost by: SENC » Thu Jan 26, 2023 6:13 pm

Thinking about your problem and rereading the first post, I wonder if the vent isn't a red herring (though it could be another problem). You're getting flooding, and I'd think lack of a vent might cause poor fuel flow rather than excess fuel flow - because fuel flow into the venturi is caused by lower pressure in the venturi than in the bowl, right?

You've selected carbs with adjustable jets, which weren't selected for the Elans - so determining how to set them is a bit of a crapshoot, I'd guess. Are you certain how they are set isn't causing too much fuel to be siphoned into the carb? Maybe an exceedingly rich condition is allowing a start and initial idling when cold bit then becoming a problem? Re the needles you've selected the right match for them? I'd have no idea how to select for adjustable jets, but know in the usual fixed jet versions that needle selection is critical.

Assuming needles and jets are ok and not allowing too much fuel to be pulled in at full vacuum, I'd look next at the cold-start device to make sure it is oriented correctly (the disk can fit 2 ways around on the same side, 180 degrees out from each other) and not allowing fuel to be pulled constantly. Do you have a gasket on that cold-start mechanism? Another potential cause is if the leak valve (rectangular vent on the same face as the bowl vent should be) is covered in some way - that would result in a rich condition, too.

Just a few other thoughts/ideas.
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PostPost by: Bits » Fri Jan 27, 2023 5:48 pm

I doubt that I will be able to find out which model of LR they were from. Or if they were from one vehicle.
One carb is marked 322T and the other 324TA - this one has the cold start device on the side.
There is a pair of 175 CD-2 Jaguar E Type Series 3 V12 on eBay for £340 inc post which have the top adjusting (fixed needle). These would probably need the jets, needles and springs replacing.

IMG_4413.jpg and
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PostPost by: SENC » Fri Jan 27, 2023 10:35 pm

This is the booklet I mentioned - it lists the various applications for CD carbs (by vehicle): https://zenithcarb.co.uk/zenith-cd-catalogue.html

If I can find my copy tomorrow afternoon I'll see if I can find the 322t and 324ta specs and also the specs for the Jag for you, but worth ordering to have on hand. I'll try to find a thread here on elan.net where I posted a picture of the Elan section. I think if you can find some with similar specs you'll be better off then you can order needles, jets, springs, etc to the Elan spec. I'm in the US, but pretty certain I have a couple spare carb bodies I could send you (can't remember if they were off a Europa or maybe a Triumph or MG) if you can't find a good match there.

Edit: this thread from my rebuild might have some useful resources:
viewtopic.php?f=40&t=41122&start=15
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PostPost by: Bits » Sat Jan 28, 2023 2:32 pm

Many thanks again for the information.
I have checked the cold start - and realised it supplies fuel to both carbs when actuated!! :D

cold.jpg and
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PostPost by: SENC » Sat Jan 28, 2023 6:53 pm

Interesting comparing that device with the same in my thread. Is there a position where fuel flow through it is fully stopped?
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PostPost by: Bits » Sat Jan 28, 2023 9:35 pm

The part with the gasket - the slot is closed when not in use and slides towards the slot on the base. Fuel then flows to the two rows of smaller slots (each row supplies fuel to one carb) when the choke pull is actuated.
How much fuel flows depends on how much the choke cable is pulled, which corresponds to how many of the small slots are exposed.
One set of holes goes through and supplies fuel into the choke on the carb it is fitted too.
The other set goes to the tube at the top which is connected to the other carb via a plastic tube.
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PostPost by: Bits » Sun Jan 29, 2023 7:28 pm

I also have another problem with both carbs.
The air valves do not drop all the way down - leaving a small gap. It should stop with a clunk, but I have never achieved this.
So I have just spent half of today to understand why.
I've managed to get one carb to close all the way but no clunk. The other one will have to wait until my patience returns. :evil:
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