I took my 1980 MGB in for the annual New York emission inspection
this Saturday. I was a bit concerned because, since last year, I had
converted from a single Zenith-Stromberg to a pair of SU HS4s. The
conversion required me to use pre 1974 intake and exhaust manifolds,
eliminating the catalytic converter which bolts directly to the one-piece
intake-exhaust manifold on the post-1974 design.
The mechanic who works on my American cars suggested that I lean
the mixture out a bit, just enough to drop the idle speed by about 50-100
rpm. That worked out to 6 flats (one complete turn) up on each jet on
the SUs. He said that the idea was to lean the mixture just enough to
drop the CO level but not enought to make the engine start to miss which
raises the hydrocarbon emissions. The car passed with the following
results:
HC(ppm) CO (%)
Test limits 300 2.5
Test results 95 0.7
Just for reference, I have the timing set at 17 BTDC @ 600 rpm, using 93
octane.
The air pump is connected with an anti-backfire kit from VB, but the gulp
valve
circuit is not connected.
Peter Schauss
pschauss@aol.com
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