Several years ago I noted that my valves had fallen under the desired
spec, so far as stem diameter. This was on what is considered to be the
late (1973) head, with the better intake manifold. So I ordered a set of
both intake and exhaust valves, along with the new guides. Imagine my
surprise when the delivered exhaust valves were smaller than the
original ones! I confirmed that the part numbers were
the ones ordered, and sent them back, asking then for the "early",
larger ones. It appears that there was a crossover, when the later head
used the larger exhaust valves. Being the original owner of my '73, I
know that neither the head, valves or their seats had been previously
replaced or altered.
All of the Big Three parts books show that the '73 uses the smaller
valves. The '72 uses the larger ones. The build date on my car was
August, 1973.
John---Any ideas?
Dick
From:
standardtriumph@btinternet.com(John Macartney) Date: Sat, Nov 10,
2007, 12:07am (PST+8)
Ken - a great deal of research work was done about 8 years ago in the UK
by a guy called Chris Witor who is something of Triumph guru. Chris
wrote a very interesting and informative article in one of the UK club
magazines on cylinder head flow properties. The 219015 and 016 heads
(the later ones) are better overall even though the later head has a
smaller exhaust valve diameter. In tests using a variety of different
heads, Chris' report showed conclusively that in terms of optimum gas
flow,
an 015 or 016 head with the smaller exhaust valve dia was by far the
best.
Jonmac
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