Lotus Elan

Stromberg Question

PostPost by: whaig » Sun Jul 07, 2024 7:56 pm

I recently removed a pair of Stromberg carburettors from my 1969 S4 Lotus Elan. I had them for sale on eBay, but the buyer returned them because the needles could not be adjusted. I did not realise this. I did a bit of research and found on a Triumph website that Stromberg created carburettors for about a year. Does anyone have any information about whether these were fitted to the Lotus Elan?
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PostPost by: Sadbrewer » Sun Jul 07, 2024 10:05 pm

My 69 S4 was fitted with Strombergs...they were a common carburettor of the day and despite what many people say, we in the garage trade regarded them as a good reliable instrument. The Triumph website is talking crap, they were making Carbs before WW1...many manufacturers used them over many decades.
From October 1968
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PostPost by: whaig » Sun Jul 07, 2024 10:22 pm

My point is the needles could not be adjusted, I have checked them. I have another elan and the needles. Can be adjusted from the top using special tool. Has anyone had similar issue with carbs that needle is fixed?
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PostPost by: rgh0 » Sun Jul 07, 2024 10:27 pm

The "emissions" Strombergs had fixed needles. I believe at least the US cars used these. i dont know whether the UK ones did at any time

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PostPost by: reds4se » Mon Jul 08, 2024 8:11 am

On the Strombergs with fixed needles you normally find the needle jet can be adjusted for height from the float bowl underside via the hexagon nut thus enabling fine-tuning of the mixture.
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PostPost by: SENC » Mon Jul 08, 2024 12:28 pm

As noted above, initial Strombergs on Elans were fixed needle - when Lotus started offering Elans with Strombergs in non-emissions markets (1970), they offered adjustable needle Strombergs. There is a Lotus Service Bulletin describing jet adjustment on the fixed needle carbs - if not in the wiki here you should be able to find it by searching this forum.

Here's the listing of variants...

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69 Elan S4
65 Seven S2
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PostPost by: david.g.chapman » Mon Jul 08, 2024 6:28 pm

My +2 has a federal engine converted back to UK spec, and has fixed jet Stromberg carbs. On my carbs the main jet is not adjustable. However, mixture adjustment can still be made as follows:

1. Unscrew and remove the damper.
2. Take off the top of the carb (4 screws)
3. Loosen the diaphragm at its edge and take off the piston, diaphragm, and needle assembly.
4. Get hold of a well fitting flat screwdriver and loosen the needle holder grub screw, accessible through a hole in the side of the piston.
5. The needle can now be moved in and out of the piston to adjust the mixture before retightening the grub screw - not too tight! The starting point is aligning the needle shoulder with the bottom face of the piston, without pulling the needle out (it's spring mounted). Then check your mixture and spark plug colour and re-adjust accordingly.

Sounds tedious but it's not too bad.

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PostPost by: TonyA » Tue Jul 09, 2024 3:44 am

I would add mark the orientation of the carb cover and the rubber diaphragm relative to the carb body before removing them.. Tony
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