Jon G.
I do not KNOW why Carter returned to the two step rod, but GUESSING testing may have shown that the 216/235 had insufficient torque to maintain the vacuum for the mid-range step on the metering rods, and that the 3-step rods were simply additional expense for these engines. Again, this is a GUESS!
As far as smog emissions are concerned:
That company with the same name as a famous country and western singer from Tennessee pioneered smog emission testing; building a laboratory in southern California that employed quite a few folks about 1960. By 1964, this company had a viable working smog emission system (obviously not to 2022 standards, but a beginning).
The California legislature was sufficiently impressed to create smog emission legislation to take effect with the 1966 model year; NOT that they were interested in smog emissions, RATHER that they figured the legislation would REQUIRE AMC, Chrysler, and GM to also build laboratories in southern California, employing more folks. Oh, and the legislation was written so that the other company's results, were not applicable, requiring they continue their laboratory!
The Feds implemented smog emissions in 1968.
I will now get off my soap box, other than to state my personal opinion that the car companies, with the consumer footing the bill, really did a good job in spite of the various government requirements. I feel that if there was NO legislation, public opinion would have created sufficient pressure on the car companies once the first system was in production; and smog would have been reduced by a significantly greater amount much quicker, and MUCH cheaper than with the legislation!
Jon
