Just to confuse matters... I think you have to be careful about what you perceive as an "E" or an "F" if you're outside the US market. For instance, there were clearly B20E's with CIS sold in some non-US markets; this combination is shown in the 1974 140 shop manual. Of course the B20E/CIS combo never happened in the US market, as the "E" disappeared with the beginning of the 1972 model year, 2 years before the introduction of CIS.

In any case, (at least on this side of the pond), I would agree:

- the "E" had no machined flats conjunctive with the right center headbolt surface

- the early "F" had a machined flat continuing forward from that headbolt surface

- the late "F" had machined flats continuing both forward and aft of that headbolt.

My guess is that all of this was also true in the European markets, but you have to remember - they apparently had "early" and "late" (D-jet and CIS, respectively) B20E heads, as well.
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Gary L - 142E ITB race car, 73 1800ES
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