Lotus Elan

Stromberg air valve orientation

PostPost by: bulfin » Sun Jun 03, 2018 8:58 pm

Hi,

Searching through the forum and reading the manual I can find nothing on air valve orientation. Does it matter which side of the air valve is facing the front, for example. Mine have two square cutouts on the bottom about an inch apart and a larger square cutout on the body at 6 o'clock. Of course I did not look when I took them out.

TIA,

Bob
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PostPost by: oldelanman » Mon Jun 04, 2018 5:05 am

Hi Bob,
The air valve is correctly orientated by two small tabs on the diaphragm which locate in corresponding recesses in the top of the air valve and the body of the carb, however, they are small and easy to overlook. Section L16 of the Workshop Manual para 8 has a brief reference to them.

diaphragm.jpg and
Last edited by oldelanman on Mon Jun 04, 2018 8:29 am, edited 1 time in total.
Roger
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PostPost by: 69S4 » Mon Jun 04, 2018 7:19 am

The devil is in the detail with a lot of these things isn't it. Roger's answer is the correct one - there's a small and easily overlooked tab on the edge of the diaphragm that fits into a small slot on the top of the mixing chamber and that sets the orientation of the air valve. If you ever have to change the diaphragm there's a similar tab /slot arrangement in the centre.

The cutouts with the holes in them need to be on the the engine side of the jet, i.e. between the jet and the throttle plate. The function of the holes is to transfer the vacuum to the chamber sealed off by the diaphragm and thereby raise the air valve. Put the air valve in the other way round so the holes are at the front and it won't rise.
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PostPost by: bulfin » Mon Jun 04, 2018 3:13 pm

Thank you both so much. I'll reread the manual and make sure they are in the correct position.

Lotus owners are a great bunch of people.

Bob
Bob Bulfin
1969 Elan S4 DHC
Mobile, AL USA
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