Assuming that SLC stands for Salt Lake City, the altitude is higher than recommended for the standard metering rod.
Carter used the standard metering rod from sea level to a maximum of 4000 feet.
4001 ~ 6000 feet used one size lean rod
6000 ~ 7000 feet used two sizes lean rod
Leaner rods are thicker than standard, thus raising the A/F ratio (higher is leaner).
Since the effective metering area is the area of the jet less the dynamic area of the rod, simply changing jets will not give the proper A/F ratio at all values of vacuum.
Jon.
