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mine appears to be 1957
thanks for info
the # on mine is ECZ-G
what is the difference in the exhaust valve 292/312 dia
it says" no heads above this point are posted" what is posted in this case?
There's not really a 312 head so don't be fooled and pay a premium for a set. The better heads are ecz-g, 113, and 471. These can be on 292, 312, and the ecz-g were also on 272s.
The Gs have the smallest chambers, 69cc
The 113s have 72cc chambers
The 471s have big chambers, 82cc, and are usually used with superchargers or turbos but were originally for naturally aspirated applications and can work very well naturally aspirated, with domed pistons.
Later Y castings were posted - this is an additional support cast above 2 of the chambers. This is usually nothing to worry about for a naturally aspirated street engine. For a supercharged engine or a race engine with high compression, it could be a concern. All 113s and 471s have this extra support. G's may or may not.
Really, after 50+ years these heads could be on any Y-Block.
Heads are interchangeable, but typically the passenger side has a plug in the rear coolant passage and the driver side has a bung for the coolant temperature sensor.
Since the heads are the same, there is no difference in valve diameters between similar castings and the 3 listed above are large valve castings which all have the same size valves.