Listers,
Thanks to several listers, my six is running smooth again. Here is
the resolution of my Stromberg carb adjustment problem on my 76 TR6. Sorry
for the length. If you'll remember, last Thursday evening, in a fit of not
leaving well enough alone, I used my special Zenith carb adjusting tool and
my new Colortune to adjust my Strombergs into the stone ages. Well, a number
of listers provided me with some extremely detailed and helpful advice. Here
is the outcome. When I diasassembled the front carb (I merely removed the
top cover and piston assembly...left the carb on the car) I found that,
indeed exactly as several people said, I had backed the needle adjustment
screw off of its threads leaving the needle in the fully extended lean
position. This was not obvious in a visual examination. If someone had not
told me specifically what to look for, I probably still would've missed it.
If you'll remember, the symptom Thursday night was that I could turn the
adjustment tool endlessly without ever hitting the stop and without
affecting the fuel/air mixture at all. So, with the air valve piston out of
the carb, I reset the needle on the adjustment threads and set it with its
shoulder flush with the bottom of the piston and then reassembled the carb.
The diaphram on the front carb looked good.
Then, I disassembled the rear carb (Thursday night, it was after I
messed with the rear carb that the car REALLY started running bad). On the
rear carb, the needle had NOT come off of its threads...instead the whole
diaphram had pulled loose from the inner plate that holds it to the top of
the piston. Therefore it was loose and air was getting past it. The diaphram
was not torn, it was merely not in place. I can tell you exactly when and
how this happened. Thursday evening when I was using the carb needle
adjusting tool on the rear carb, I was trying to turn the allen key while
holding the outer barell of the tool firmly. The needle adjustment screw
was not turning very easily and in the process, the barell of the tool
slipped my grip and turned about a quarter of a turn and I felt something
give. I guess that I turned the whole piston and consequently pulled the
diaphram from under the mounting plate. The diaphram wasn't torn but I was
worried that it may have stretched, so I replaced it with a new diaphram
that I had from a pair of carb rebuild kits that I had sitting on my parts
shelf. (I usually try to keep my shelf stocked with gaskets, filters, and
other bits that are not very expensive but very irritating to find yourself
without on a Sunday afternoon. It also helps me meet that minimum shipping
charge. ;-)) Anyway, I then adjusted the rear carb's needle to where its
shoulder was flush with the bottom of the piston (a couple of people on the
list suggested this in order to have both carbs starting from exactly the
same adjustment setting). Then I reassembled the carb and fired up the car.
Already, it ran much better but it was still a little lean. So, I CAREFULLY
enriched the mixture adjusting each carb in the same increments until it
sounded right. I didn't bother using the Colortune on it.
The car is now running as well as it ever has, but there is one more
mystery. In the book, it tells you to, with the engine warmed and running,
remove the air cleaner and lift and hold each carb piston about a 1/4 inch
with a screwdriver as a test of fuel/air mixture. If you are too lean, the
car's idle will drop drastically and it will try to die. If you are too
rich, the car's idle speed will increase. And if it is correct, I think it
said the car's idle will momentarily increase and then return to normal.
Using this test, I found my car was trying to stall when I lifted the carb
piston. I adjusted the mixture needle all the way up into the piston to its
stop at full rich position but the "lift the piston 1/4 inch" test still
caused the idle to drop and falter. Why? What am I doing wrong? It did this
on both carbs. Anyway, it doesn't really matter, I adjusted the needles to a
point where the car is running very well regardless so I think I'll leave it
alone. Thanks again to everyone for their help! Regards, Greg Hutmacher
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