Strange 3946074 ( ZL-1 & L-88 ) heads

[nuch_ss396]

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Hi, When GM cast the first batch of D port ex port heads they had the 074 casting #, the part # was different than the 074 round port casting part # a few months after they changed the casting # to 077. I had some of these D port 074s when new, I think around 1980.
Jerry

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Jerry,

Are you certain about this? I would have thought that the
change to the exhaust ports would have mandated a different
casting number. Think of the early 3933198 ( ZL-1 & L-88 )
intakes. GM used the standard 3933163 intake, milled down
the divider, then removed the "163" portion of the casting
number and stamped in a "198" in their place.

I would expect GM to do the same with the '074 heads with a
drastic change cast into the exhaust ports.

I'd like to hear more about this.

Steve