Vance---I finally took the time to look at all records of work done,
before and after I started doing my own. I have them all, even from the
first oil change when the '73 was still under new car warranty. I found
nothing in these bulging manilla envelopes that suggests that the valves
were changed and the seats altered to fit. This
would've been an expense item too large to be overlooked by me or a
I have had the valves ground three times by outside shops during the
last 25 years. The valves were replaced the last time, but I furnished
the valves. (Stainless exhaust, as were the originals)
Remember that forced induction engines get away with murder when it
comes to breathing,
If larger valves causes a power drop, I wouldn't know it. The car runs
better than any of the dozens of TRs I've driven, even in the naturally
aspirated mode. Then again, maybe I'm partial to my pet of 34 years!?
Ummm. Have you had the
engine overhauled before? Could the machine shop have upgraded the valve
size as part of a rebuild?
If you do some judicious
reshaping of the combustion chamber in the vicinity of the valve, then
this will be good for some power. If the chambers were left stock, then
most likely power fell or stayed the same.
From: owner-6pack@Autox.Team.Net [mailto:owner-6pack@Autox.Team.Net] On
Behalf Of Sally or Dick Taylor
Sent: November 10, 2007 1:26 PM
To: John Macartney
Cc: firstname.lastname@example.org; email@example.com
Subject: Re: [6pack] Early vs Late Head
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
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