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By darrell - 4 Years Ago
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i have tried several times to find out when they stopped using core plugs in 56 heads.does anyone know and did dif and cf heads change at the same time.
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By carl - 4 Years Ago
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Not sure when they quit but 56 mercury 312s had them.I think they were marked ECZ C but will have to look to make sure Carl
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By paul2748 - 4 Years Ago
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I don't know when either, but both styles were ECZ-C heads
darrell (9/15/2020)
i have tried several times to find out when they stopped using core plugs in 56 heads.does anyone know and did dif and cf heads change at the same time.
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By Ted - 4 Years Ago
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I have ECZ-C, ECG-D and ECL-A heads with and without the core plugs in their ends. My understanding is that the core plugs were required as part of the casting process. As soon as it was figured out how to cast those heads without the core plugs, the holes for the core plugs went away. Eliminating the core plugs in the heads simplified both the casting process and the machining of the heads. This also increased the production numbers which would have been a big deal. One pair of ECL-A heads I have that’s without core plugs still shows evidence where the core boxes were simply filled in at the core plug area and the heads were cast using those older core boxes.
Going through all those heads and recording the casting dates would give a better idea as to when the elimination of the core plugs took place. Without going into detail in cataloging when the actual change took place, it would appear to be in early 1956 but that might not hold true for all the different head castings. Also to be taken into consideration would be if the heads were Dearborn or Cleveland castings as that would also make a difference on the timeframe and especially if both foundries were casting the same head as in the case of the ECZ-G heads.
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