Lotus Elan

Weber carb question

PostPost by: alfert » Tue Aug 02, 2011 4:00 pm

I have a 67 coupe with a fresh, totally stock engine. It has new DCOE-151 carbs and I am trying to get the car to run properly. I started to check the float level and have a simple question. The floats are the black plastic type and I don't know what to set them at. The older round floats were easy to measure, but the triangular ones, are difficult. Where do you measure? and what should they be closed and full droop? Any help is appreciated.
Thanks,
Brian
alfert
Second Gear
Second Gear
 
Posts: 105
Joined: 10 Oct 2003

PostPost by: gjz30075 » Tue Aug 02, 2011 4:32 pm

I followed the guidelines from this forum:

http://www.alfabb.com/bb/forums/carbure ... ement.html

With new 151s, I would go over all fasteners to be sure they are properly torqued. I found very loose ones and overly tightened ones with mine. I found the air bleed adjustments very useful to fine tune them.
Greg Z
Greg Z
45/0243K Sprint
36/5727 pre airflow coupe
User avatar
gjz30075
Coveted Fifth Gear
Coveted Fifth Gear
 
Posts: 2973
Joined: 12 Sep 2003
Location: Roswell, Georgia, USA

PostPost by: Esprit2 » Tue Aug 02, 2011 6:12 pm

Brian,

Standard box-stock Weber DCOE float settings are:

Brass (older production)
Float Height ..... 8.5 mm
Float Drop ...... 15.0 mm
Float Weight ... 26 gr (0.9 oz.)

Plastic (Black, new -151 & -152 models)
Float Height ... 12.5 mm
Float Drop ...... 25.0 mm
Float Weight ... ?? gr

Some applications took liberties with the float height to promote overall rich or lean conditions; but if you don't know the specific float height, use the standard Weber height. Since Lotus never used the 151 model or the plastic floats, you're kinda on your own. I'd default to the 12.5 / 25.0 mm numbers and tune from there.

The float height measurement is made with the carb cover held vertically, float hinge upper most, the floats hanging down and just lightly resting against the inlet valve. With the cover gasket in place, measure from the float to the gasket face, not from the float to the metal cover face.

In the Alfa site referenced previously, one writer posted marked up photos and said to measure from the top of the float as it hangs vertically (see the photo). That's the first time I've seen that measuring point called out, and most manuals show the measuring point as being the bottom of the float (as shown in that photo).

In the Alfa site referenced previously, one writer posted marked-up photos and said to measure from the top of the float as it hangs vertically (see the photo). That's the first time I've seen that measuring point called out, and most manuals show the measuring point as being the bottom of the float hanging as shown in that photo.

It's my opinion that the difference is in the Alfa guy?s interpretation of ?top?. Manuals typically refer to the side of the float that faces up when the cover is in the horizontal/ as-installed position as the "top". Then they specify measuring from float ?top? to gasket face? but ?top? doesn?t change just because the cover has been rotated to vertical (ie, your right hand is still your right hand even if you turn around). IMHO, the Alfa guy?s version of measuring from the "top" of the float is unique and a little off the norm.

Regards,
Tim Engel
Esprit2
Third Gear
Third Gear
 
Posts: 371
Joined: 02 Apr 2008
Location: Twin Cities, Minnesota, USA

Total Online:

Users browsing this forum: No registered users and 5 guests