Lotus Elan

Dellorto Float Height Confusion

PostPost by: William2 » Thu May 18, 2017 5:37 pm

Sorry to start up yet another topic on Dellortos!! Having read a lot of previous threads there seems to be conflicting information about float height settings. My Dellorto 40Es' have 10 gram floats and I intend to go with the Lotus advice and set them to 15mm, having experimented with 16mm. However, I noticed that on an American Dellorto website that the recommendation is 17mm for this weight of float and also a strong warning to only use Viton tipped needle valves. Are Lotus suggesting 14.5mm to 15mm because that suits the Twin Cam engine better or could it be partly due to the fact that the engine is canted over slightly on its mountings possibly affecting fuel levels? On my car I had to use the same mounts either side (level engine) to get the cam cover to clear the bonnet.
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PostPost by: Robbie693 » Wed May 24, 2017 12:14 am

I'll be checking my float heights this week too, I don't remember which floats I have but I was intending to use this guide from Tim regarding float heights for each weight- http://www.lotuselan.net/forums/lotus-carbs-f40/dellorto-advice-t32497.html (about halfway down the page).

Pertinent info reposted (with acknowledgement to Tim Engel) :

DHLA
Float ...... Float
Weight ... Height
10 gr ...... 16.5-17.0 mm
8.5 gr ..... 15.5-16.0 mm (Lotus calls for 14.5-15.0 mm = 1.0 mm higher = richer)
7.0 gr ..... 14.5-15.0 mm

By the way, Des Hammill gives one float height for all float weights... 15.0 mm. I suspect you'd have to do a little additional tuning to make that work universally. I always use the engine manufacturer's spec, and drop back to the three settings given above if the mfgr's spec isn't available. With Lotus, I also presume their setting will be 1.0 mm higher than the Dellorto default (that presumption works on the 907 & 912 as well).

A heavier float naturally rides lower in the pool. So for a given fuel level, a heavier float will be lower = larger number. Conversely, a lighter float will be higher = smaller number. So, in the pursuit of one correct fuel height, all three of the above standard weight & height combinations should produce the same standard fuel level.

Note that for the 8.5 gram float used with the Twin Cam, Lotus specifies a 1 mm higher float height, which will give a 1 mm higher fuel level, and an overall richer condition in the carb. If you wish to tune your engine the way Lotus set it, then use Lotus' specs, and not generic Dellorto specs.
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