the "wide" head, as many seem to call it, first appeared on the TR5 in
1967. My TR5 still has its original head
in 1968 the GT6 & Vitesse models got a thinner version of this head
(different combustion chamber volume), . In 1969 a few 2000 sedans were
built with this "thin" head and some other block changes, but it did not
become widespread in UK or Australia until the 2.5PI sedan of 1970. At this
time, the TR6 PI was well underway and used the exact same head/engine as
the TR5
When the GT6 changed to domed top pistons, it allowed the same 'thick" head
casting to be used on both 2000 & 2500 engines, but there were still subtle
differences in the heads
none of the above referenced models used the US style TR250 head with its
narrow port spacing.
why it took till 1971 or 72 to change the head to the more universally used
type, is unknown to me.
hopefully, can someone shed some light on this ??
Terry
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