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Uncle! Was: lean and leaner

To: IfixMGs@aol.com
Subject: Uncle! Was: lean and leaner
Date: Tue, 4 Jan 2000 21:25:00 -0500
Cc: spridgets@autox.team.net, midgetspriteclub@listbot.com
References: <0.c8d3da31.25a3d151@aol.com>
Well I just got back from checking everything. The jets are centered 
and the floats are at the correct level (as near as I can tell 
between 3/16" and 1/8") and are not leaking and the pins are not 
loose, the needles are true and set in the pistons at their 
shoulders, the pistons rise and fall smoothly. All this is as I 
expected since the carbs were rebuilt this summer by Jim Taylor. 
According to the data sheet that he supplied, he replaced the floats 
and valves, the piston springs, needles, seats, and jets. Both bodies 
were reamed and oversize shafts fitted. Again, these carbs ran nearly 
perfectly for several hundred miles following the rebuild. The float 
valves that Jim installed are ball rather than needle valves and 
don't appear to be adjustable, but again, they look to be set right 
between the workshop manual specs.

Anyway, after checking the above, I reset the carbs, this time with 
all between-carb linkages disconnected. The carbs are drawing evenly 
and only required 1/2 turn to give a good idle at 850-900 rpm. Still, 
the mixture on the front carb is only 6 flats down and the rear is 2 
flats down. This is better than last night, where it was 3 down and 1 
up, respectively. These mixture settings give a smooth idle and good, 
smooth acceleration up to about 3100 rpm in second, at which point a 
flat spot is reached with coughing exhaust. This is alleviated by a 
quick tug on the choke.  Above this rpm, acceleration continues and 
choke is not needed.

I am now out of time on this job. I need to have the car for highway 
travel this weekend and don't want to hole a piston due to an 
over-lean cruise, so I think I'm going to take it to my local LBC 
mechanic, Neil Estes. He's good, reasonably priced, and works 5 
minutes from my house. No doubt this will turn out to be an obvious 
fix. I am morbidly curious at this point to see what he finds. I'll 
let everyone know what it turns out to be. Also, apologies to all 
those in the past who I told "tuning SUs is easy." It's easy as long 
as everything goes by the book.

Jeff

Thanks to all for the suggestions.
---
On 1/4/00, IfixMGs@aol.com wrote:
>Jeff -
>    Sometimes a loose float pin will allow the float to vibrate and raise the
>fuel level. Once the level gets high enough, it dampens the vibes, and
>reduces the seat bypass while enrichening via the jet.... I knew that 4 years
>of engineering school and 2 years of post grad philosophy would SOMEDAY come
>to good use....... Mark

Jeffrey H. Boatright, PhD
Senior Editor, Molecular Vision
http://www.molvis.org/molvis
"Seeing the Future in a Very Tiny Way"

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