No, the lean idle calibration didn't come until several years after the
closed crankcase system. I'm not sure exactly when it did happen, but I
would guess it wasn't until 1975 or so. The "lift the piston" test
should work fine on your TR4.
Since AFAIK the only spec for the lean idle is exhaust CO content, a CO
meter is the only practical way to set it accurately. There are other
methods that would work (for instance propane enrichment/idle speed
drop), but someone would have to work out a spec.
59 TR3A daily driver - no emission controls at all
63 Sports 6 - ditto
Dylan Pedersen wrote:
> Randall wrote:
> I've lost track of which car this thread is about, so I'll just throw in a
> caveat :
> The "lift the piston" test does not work for later cars with US emissions.
> It will always indicate lean, because the emission carbs were calibrated to
> run lean at idle, to reduce CO emissions.
> Hi Randall - Is this true for all Triumphs with emissions controls?
> If so, how do you set the fuel/air mixture while the engine is idling?
> I ask because I'm in the middle of a carb rebuild and want to set the
> mixture correctly.
> I'm working with my '63 TR4. It has Zeneth-Stromberg CD175 C1825s. The
> only emissions control I have found is the re-breather going from the valve
> cover to the air filters, so I don't think I'll have the problem you
> describe, but I'm curious none the less.
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