Richard----You should be able to get very close to "ideal" performance,
when using the ZS carbs on a basically stock engine, without using $$$
equipment. If alll cylinders are pulling (vacuum) evenly, measure the
exposed parts of the carb needles at the base of the air valve, using a
vernier caliper. Set them evenly, and then adjust up or down equal
turns/amounts.
To know relatively quickly if you are rich or lean at idle, introduce
"air" into the system. Easily done by disconnecting a working *vacuum
line. If the engine speeds UP when the vacuum line is disconnected, your
carb settings are toward the rich side. Conversly, if the engine speed
drops, you were either right on the money, or a little lean.
*Holding your thumb over the vacuum line to control the size of the
opening can tell you how close you are to "ideal".
Almost as good as an 02 sensor!
Dick
From: richard.r.olson
I'll ask the question here, everything else is just background:
Is there any way, after a ZS carb rebuild, to tell if the A/F mixture is
'good' without using a $$$ commercial tester or building your own ? I
loaned out my Bentleys, so I forget if there's a procedure to blind set
the mixture prior to installing rebuilt carbs. And I've tried the 'lift
the air valve and listen to the idle' but results were inconclusive.
Background:
'72 TR6, stock engine, unknown miles ( I put on 30K), Idled
poorly, did not stay at one RPM, varied about a lot, but all other
performance was good (no missing/stalling, decent acceleration), RPMs
went up a lot when starting fluif was sprayed along the throttle shafts.
Figured the shafts could use replacing during the rebuild.
I had a spare pair of ZS 175 CD (not 175 CD2's) that I bought from TRF
in
1992. They called them "Blue Tops" for the color of the damper rod
plastic top. The only other visible difference from the original carbs
was that the choke lever has 2 spring loaded detents or stops where the
originals didn't.
Rebuilt the older carbs, set mixture fully CW, then went CCW 1.5 turns.
Installed in car, started right up.
During the road test the performance was good under hard acceleration
and idle was improved. However, under gentle acceleration, or just
barely pressing the pedal, the car seems to buck slightly with a slight
'blurble' in the exhaust tone, This condition was not present with
the original carbs.
OK, I'll ask another question: Could this condition be related to too
rich mixture? Which brings me back to my original question at the top of
the post......
TIA
Rick Olson
1972 - CC78827U/5 <- no overdrive here :-)
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