In a message dated 12/10/98 3:23:50 AM !!!First Boot!!!, EISANDIEGO@aol.com
writes:
<< We have encountered a challenge in doing the valve job on the 73 GT6
(Street
car). The head has the appearance of the early heads - although the previous
original owner stated he had done no engine work. The replacement valves
needed for the head are different than factory standard specifications.
Neither the standard intake or exhaust valves that should fit this early head
are fitting properly. The previous head gasket and intake/exhausgaskets match
the replacements ones which were for the early head. Anyone out there
experienced a similar situation ?
>>
Cary-
Be glad to tell you more than I know...
First, let's dismiss the v early head style as on the early MK I cars (intake
and exhaust ports about on the same horizontal level, as opposed to later cars
where the intake ports are noticeably higher than the exhausts).
The usual head on a GT has kept the same port spacing throughout, so the
gaskets will be the same. The GT head spacing is the same as the LATE TR6
head. This came about because the GT head was supposedly derived from the TR5,
while the early TR6 was a completely different casting. In the TR6 range, the
earlier valves were larger than the later valves (an effort to stop cracks
between valves). The GT head should have the large sized valves throughout.
That said, I have seen later GT heads (the thicker ones) with the small
valves. This may be the root of your problem. I can't remember exactly what
the thickness changes to the heads is, but I think that the MKII early head
measured 3.330" thick (from face to machined area of valve cover gasket (or
head stud) interface). If the valves you got are too large, you can either
open up the seats for that little extra breathing room, or order a set of late
style TR6 valves.
Of course size may not be your problem, in which case...nevermind
Size does count...
Nick in Nor Cal
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