Weber 40-45 DCOE Experts - Proper Float Level?

A long time ago someone very knowledgeable about these things told me that the very easy way to check for a correct float level on DCOE carbs was to simply pull one of the emulsion tubes (which hold the air and gas jets) and see where the fuel level hit on the emulsion tube(s).

Really easy to do and great advice. Fantastic. But two small problems, I don't remember where on the tube he said was the "correct" level and 2) it's really, really hard to see exactly how high the fuel comes up on tube, even after wiping it off first and reinserting.

So, regarding problem #2, it's an easy fix -- just use a black tiewrap as a dipstick into an empty emulsion tube hole. You can easily read the fuel level on that and then translate that to the tube.

Regarding problem #1, clever me decided to RTFM (Read The F___ Manual). Guess what, none of the manuals tell you where the fuel level in the bowl should be. Sure they give you the correct float settings. (You know, remove the top, hold the top assembly vertical and measure from the base of the top to the bottom of the brass float, etc. etc.) Well guess what; there ain't no brass floats around these days, only plastic which ain't round but rather oddly trapezoidal or some such shape.

Not to be discouraged, somewhere I read that for the plastic floats should be 12mm or until the bottom of the float is parallel to the top (instead of the 8.5mm specified for the round brass floats). Guess what, to get the plastic float parallel to the base plate requires a 15 mm gap.

So damn the torpedoes, full speed ahead. After setting the floats at 12mm gap (and not parallel), much popping and farting at idle -- Fuel level clearly too high. So I reset 'em to be level which turned out to be a 15 mm gap (see pics). Now idles fine. Gaining on it.
http://teamterrificracing.net/RMVR%2...E_Pics_web.jpg

(To see a much higher res image of above, CLICK HERE)

The standard Weber DCOE schematic for the fuel during the normal power stage (see pic) would imply the fuel should come to point "A" on the attached picture of a tube. As noted, even at 15 mm gap (i.e the float bottom is parallel with top's base) the fuel level is way higher than the schematic would suggest. And, at idle it runs great.

But it still seem to me the gap setting on the floats is only "correct" if it results in the appropriate level in the bowl to run well at speed. Thus question remains. What is that "correct" level for fuel (not float gap) when using the emulsion tube observation which would seem to me to be the very best way to gauge it? Then set floats to get that level.

Any thoughts or suggestions? As usual, thanks to ApexSpeed for all the residnet expertise.

There is a weber side draft forum run by one of my Lotus Elan friends. The forum a restricted group, but its easy to request access.

He discovered a means of direct measurement of correct fuel level in the emulsion tube wells. He is an instrument maker by trade (Lawrence Livermore National Lab) so he understands measurement theory.

Cut a piece of paper or thin card stock into a strip 3/16" wide by 3" long.
Mark the strip of paper 25mm from one end with a pencil.

Engine fully warmed, running at idle, carbs synched.

• Remove the jet covers.
• Remove one emulsion tube assembly at each carb.
• Stick the paper into the e-tube well and note if the paper just wets with fuel with the mark at the edge of the top cover. If the 25mm mark is even with the emulsion well opening, you are good.
• You can reuse the paper strip, just allow the fuel to evaporate from the strip.

If not, then-
Adjusting float levels:

• Remove the carb cover
• Use a fuel banjo with gaskets and connect 2psig air hose to the banjo on the fuel port of the carb top cover.
• Turn the carb cover upside down.
• Measure the gap between the float and the underside of the cover gasket.
• Air should not leak by the needle and seat.

Determine where the needle lifts off the seat.

• Roll a drill bit between the float and cover.
• Incrementally increase the drill bit diameter until you can hear the air start to leak across the needle and seat.
• If you need to go up 1mm, use a 1mm smaller drill bit and bend the tabs until the smaller drill bit barely opens the needle from the seat, listening for air.
• If you need to go down 1mm, use a 1mm larger drill bit and do the same.
• Replace the top covers and repeat your level check.

Hope this helps.


https://groups.yahoo.com/neo/groups/...t_central/info

Got it. Thanks, Dan. Great detailed info. Basically that's how I went about it, But for using a a tie-wrap dip-stick instead of rolled up pager. But rolled paper would be even easier to "read." (A lit cigarette probably not a good idea, huh? But the right size!)

Not exactly sure what if "the 25mm mark is even with the emulsion well opening" really means. However, since 25mm is just sort of an 1" (.984) and based on the calipers shown in my picture which are open to about 1.25", it appears the correct fuel level would be just about between the "A" and "B" points in the in the picture, Or about midway on the fat barrel portion of the emulsion tube.

http://teamterrificracing.net/RMVR%2...e_only_Web.jpg

I'll set the floats to get that result, run it Aug.2-3, and report back. I'm amazed that all the Weber manuals don't provide this bit of wisdom for easily checking fuel levels. Seems so logical and important.

Many thanks. Good info.

The 25mm reference is from the machined surface at the top of the emulsion tube well.

The hard part is seeing when your zip tie breaks the surface of the fuel when the engine is running. You can measure within 60 seconds of engine stop, but the needles want to weep fuel until the residual fuel pressure is released.

"The 25mm reference is from the machined surface at the top of the emulsion tube well."

Oh. Measuring from the top down to the fuel. OK, I can still figure out where that 25 mm would be and likewise how far it would be from the bottom (which is easier to observe on the dip stick) .

The issue with Webers (all) is not only float height, but float drop. Not enough and it can run low on fuel during on a long, full throttle run.
Too much and it could "hang-up" in a long sweeper.
You can't measure the drop with the top still on.

Thanks. Got it. I'd always wondered about the "why" of too much droop. Yes, whenever I set floats (to get proper level relative to the emulsion tube) I also adjust droop. I've been adjusting for droop by adding about 6mm to whatever the float gap is for starting to close the float valve.

FYI to everyone, additional verbal input of interest: The inclination of the carbs (i.e. if not 100% horizontal to the ground or perhaps "rake" on the car impact the "correct" level of fuel. This is another reason that the traditional way of measuring/setting floats (i.e. gap to base) can be wrong. Setting the float gap to manage the fuel level in the emulsion tube bore is really the proper way to set float levels. It seems consensus that fuel just barely below the inlet from the bowl into the emulation tube orifice is the real target for fuel level. That would correlate to be near the top of the barrel ("B" in my photos) of the emulation tube. But no higher as raw fuel will spill into the otherwise proper fuel/air passage way.

Bob,

I take a small, about 3mm, allen wrench and I put a small 'O' ring at 25mm from the end.
Then look down the emulsion tube bore with a flash light, slide the alllen down the bore to where the allen just hits the fuel, it will wink at you when you touch it, then see where you are in relation to the 'O' ring. At least that's how I do it. David

Just found a Steve Jennings document on the 45 DCOE carbs used on a BDD
he says .0560" and the droop should be set so that the lever is just clear of the ball

I do need to check the fuel level on the tube though

any new ideas on this post ?

DCOE Float adjustment


Weber Redline bulletin circa 1985-1990

"the float height is set by bending the tab on the float ball.....The height 14mm is measured from the gasket to the top of the PLASTIC float, without the weight of the float depressing the ball in the needle valve. After setting float height, set float drop for 1.5mm of travel. (of float). Adjust by bending the tab on the float resting on the outside of the seat area.
FUEL PRSSURE 2 to 2.5 psi.


Weber Redline Carburetor Applications ca. 2002-2203

DCOE...Early style brass floats 8 to 8.5mm, at radius of float to lid with gasket. Late style plastic float 12.5 to 13mm at extreme tip of float. All setings are gasket to float.
2.5 to 3 psi.
For agressive off road use, float drop s/b limited to 1. to 1.5 mm.

Haynes Book........@ 1979, 1980, 1984

Float level with brass...... 8.5mm drop ... 15 mm
no dims for plastic floats (published before plastic)

All the above are out of the respective books.....translated to Italiinglish.

My comments....I use the lid off system and a metric drill. Takes just a few minutes.
Using Nitrophyl floats you might have heavy floats as they tend to get gas soaked.

all text book stuff is for road going cars and a good base for most applications
however the full race BDD engine with 45 DCOE is a different beast which involves the gurus who know these engines. such is steve Jennings who uses a custom needle seat without a spring and has specified .560" with the droop set at just away from the ball.
does anyone have information based on these engines, carbs and seats ?
cheers