Listers:
I hope you are having a very happy Christmas day.
I would appreciate some help on (again) carburetor adjustment. I have read
the Haynes carb manual and Nelson Riedel's articles for background.
First, I was having some problems with my front carb running rich. After
checking it out thoroughly, the only problem I found was a leaking O-ring
which
led to loss of dashpot oil. I ignored that problem for a while and adjusted
the mixture so that all 6 plugs had the correct color and the car ran nicely.
Yesterday, I took apart the top of the carb and replaced the O-ring with one
from the hardware store. That solved the dashpot leak. The diaphragm
looked very good, perhaps replaced by the PO. I reassembled the air valve,
carefully checking that the needle retracted and extended with the adjustment
tool.
I reassembled the carburetor top, making sure that the 2 vent slots were on
the manifold side. I made sure the carburetor top was replace in its
original position. The air valve opened and shut nicely. I followed Nelson's
advice and screwed the needle position to maximum clockwise (full rich), then
backed off 1 full turn. I warmed up the car, then cleaned the plugs to make
sure that they had a good baseline appearance. I synchronized the carbs with
the tube method (works for me) and set the idle. Then I tried the air
valve/screwdriver method to check the mixture on the front carb, but I never
can seem
to get reliable information from that test. Finally, I buttoned it up and
took it for a test drive. The car bucked and sputtered on acceleration under
load from 2000-3000 rpm. From Nelson's article, that indicates a lean
mixture, so I pulled out the choke and it seemed to get a little bit better,
but
not much. I richened it by 1/2 turn. No change. Then I tried the opposite,
going back to baseline and then leaning it by 1/2 turn. No change. I have
tinkered with it for the better part of 2 day trying different mixture
settings, but to no avail. I took the air valve apart again to look for
problems
with the way I assembled it, but it looks good. And I will say that the
dashpot oil leak is fixed!
Any suggestions? The car will start fine, run smoothly until I put my foot
into the throttle, then buck, stumble, and sometimes backfire when I do so.
I'm frankly surprised that having only one carb misadjusted could make it run
so badly. Plugs 4-6 continue to be picture-perfect. Plugs 1-3 seem to get
a modest black coating, but not too bad, and it hasn't changed on the short
test drives I have been taking. The car runs so badly that I hesitate to take
it for a longer test drive.
Thanks as always.
Michael
'76 Tahiti Blue
CF 57044U
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