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Discussion Starter #1
On my original '66 389, are there multiple 093 head options?
Or are all 093 heads the same, as long as the 093 is stamped on the side?

I ask because a machinist was telling me mine weren't for the GTO. My 093 stamped heads have a B and a C stamped in some 2nd location and the machinist is thinking it it should be an X or a G.
 

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093 should be found and is cast on the center exhaust port. This is a 1966 only head for GTO and the 421HO. It will be a closed chamber head with 1.92" intake & 1.66" exhaust. Here is the complete casting number which should be on your head: Alamo Area Chapter of the Pontiac-Oakland Club International (AACPOCI) Here is a little more info where to look for the number: https://books.google.com/books?id=MGzXnpw2xwoC&pg=PA345&lpg=PA345&dq=date+codes,+1966+pontiac+GTO+093+heads&source=bl&ots=fxaInW9qyB&sig=GPxl2GJF2UlrZnSMqRk608kcoNY&hl=en&sa=X&ved=0ahUKEwjir9ai0ofMAhVFXh4KHSxuAkIQ6AEIIzAB#v=onepage&q=date codes, 1966 pontiac GTO 093 heads&f=false

Hope your machinist is reputable - he may not know anything about Pontiac engines, its not a Chevy. :nonod:
 

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Discussion Starter #3
Thanks for the reply, Jim. Here's a pic of mine. I definitely have 093, but what's throwing off the mechanic is the B stamped on the right exhaust port and a C on the other right exhaust port. What do the B and C mean?




Extra info- inside next to the center rocker studs, is stamped
D286
2093 on one

D26
2083 on the other
 

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The large B and the large C, cast, not stamped into the end exhaust port area are simply designations of the series of casting boxes used to cast the "093" casting heads. There are various castings of these for the 093 heads, as well as there several for the lower horse 092 heads. There is no specific higher horse 389 version or higher horse 421 version of the 093 head.

Now if one goes back to '63 and '64, there were different versions of the "714" heads, due to different machining of the valve spring pads. That particular head, used for various performance 389's and 421's, and on all '64 GTO's, will have small secondary stampings on the center exhaust area.
 

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PH knows his stuff, so accept his explanation on the "B" and "C" castings. Your head casting dates are when they were cast - D=May, the second and third digits are the day, 2=2nd day, 28=28th day, last number is the year 6=1966. These are 1966 heads. The 2093 is correct and the other is also 2093 except the casting is poorly done - saw another set for sale on the internet that had a poor casting and it appeared to be an "8" but looking hard it is a "9". Again, 1966 GTO heads. :)
 
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