I am trying to identify (date) a NH barrel (external pushrod tube type), and cannot find any info in the knowledgebase on how the height of the spiggot at the top of the barrel differs between early and later models.
I understand the depth of the recess in the cylinder head also matches the barrel, so a deep recess head cannot be used with a lower spiggot height.
If anyone has this info available, including when the changeover of types occurred, perhaps they could post it.
If the info is already on the knowledgebase, but I have not used the right search terms, please let me know. If not, could the info be added once verified.