Lotus Elan and Lotus Elan Plus 2 Forums

I looking to buy a float height gauge. They are available 5-9 mm in 0.5mm increments. What size do I need for the above carb, please?

Malcolm

8,5 + 15mm sandy

Sandy,

I read the work of Keith Franck, an American gentleman who runs a web site called sidedraft central. He states that the fuel level should be set at 25 mm below the top of the carburettor, as the method given in the manual does not take into account variations in the weight of the floats. Having checked my carburettors, I had to adjust the floats differently to achieve the same fuel level on both carburettors.

Be polite and Keith will be very helpful.

Richard Hawkins

Take a look at Keith's original white paper on making an optical sight gauge from a piece of lucite round stock. You can find this at most hobby shops. One of the first things I did back in 2006 when trying to tame my Webers. Makes a huge difference in the way the car runs. Far better than the factory method.

I agree it is better to measure the fuel level from the top as stated above.
Even easier is to measure from the rim of the jet cover.
Fuel chamber top is 16mm down from the rim, so 25mm is also 41mm from the rim.
Make a simple dipstick marked at 41, a cocktail stick or similar will do it.
Remove one of the large jet stacks and lower the stick in, watching with a small torch.
When the stick touches the fuel, the surface will shiver noticeably.
I use a Vernier depth gauge because I have one, but it not necessary to use that.
Keith Franck insists that the level must be below the top of the fuel chamber by 25mm, plus or minus 1mm.
This applies to all Weber DCOE 40 and 45 types.
Even Keith says that his optical device is no better than a dipstick and he no longer recommends it.
Hope this helps.
Eric in Burnley
1967 S3SE DHC
Edited for spelling mistake

+1 for the above.

John

Gentleman,

I cannot thank you enough for this information, I especially like the dipstick method!

Although I grew up with twin 40s, (I've spent too much time in recent years around fuel injection and maps), it is the first time I've set about to properly understand, clean and service them.

As a matter of interest and so that I can see what is installed, what were the factory jettings/chokes for this carburettor, as fitted in 1966 to S3 engines (non S/E, U.K. Market)?

Thanks
Malcolm

Malcolm,
According to the workshop manual, Technical data, page 14

For 40 DCOE18, Standard engine

Choke 30mm
Main jet 115
Air corrector jet 200
Slow running jet 45 F .9
Acc. pump jet 40
Starter air jet 100
Starter petrol jet F .5/100
Emulsion tube F .11
needle valve 1.75
Air trumpet length 1.75"

I think the first four and the emulsion tube need to be checked first.
Cheers
Eric in Burnley

Doh!
I really should have looked there before asking!
Thanks, Eric.

Malcolm

Does anyone have a copy of the Keith Franck white paper. I keep seeing it referenced but cannot seem to find the paper?