How are you going to remove the head without removing the timing belt?
~~~~~~~~~~
I believe it is possible to replace the valve seals using compressed
air to hold the valves closed.
Something like a large socket with the side ground away can be used to
compress the valve spring and remove the keepers.
You still have to remove the camshafts.
Doesn't make any sense to me to try just the exhaust to avoid removing
the timing belt.
What is so difficult about removing the timing belt?
Let me answer my own question.
The most difficult thing about removing the timing belt, is removing
the side engine brace with very limited clearance to reach the lower
two bolts.
Secret?
Remove the crankshaft pulley first, then you can reach those bolts much
more easily from beneath.
How to remove the crankshaft pulley bolt?
Electric impact wrench worked on mine.
Then later acquired a high torque air driven impact gun for the axle
nut. This would be more than adequate for the crankshaft pulley bolt.
An impact gun allows you to remove the bolt without the engine turning.
~~~~~~~~~~~~
My personal opinion.
Not worth changing the valve guide oil seals if they're just going to
start leaking again.
However, that puff of smoke on cold start could shorten the life of the
oxygen sensor, and I was getting (sometimes) a large cloud of blue
smoke which just didn't seem right.
The following worked for me.
First, having acquired the car with 80,000 miles - conventional oil
changed at 5,000 mile intervals, I changed the oil more often several
times.
Then added auto-rx (auto-rx.com) and drove 500 miles on the freeway,
drained the oil, added Mobil 1 10W30 and 3 cups (20%) Lucas heavy duty
oil stabilizer.
Problem solved.
That was in August of 2002, still no problem.
Oddly, I too, will not use most motor oil additives. Many have been
proven useless or harmful and the companies fined for deceptive
advertising practices by the FTC.
I do not like the idea of adding anything that doesn't belong in the
engine or could alter clearances.
The Lucas is a pure petroleum product with no solvents or particulate
additives.
If the viscosity is 50w, the effective viscosity of the blend when warm
is 34W - not excessive in my view. But the Lucas is different than
10W40 for example, in that it clings to parts and doesn't seem to drain
off over night.
I searched these groups extensively before first use, and of those
actually having tried it, they seemed to have around 300,000 miles on
the engines and be pleased.
It does not "swell the seals", so in theory, you can just drain it back
out and be back to the original state with no harm done, but I've
continued to use it because that blue smoke on cold start is gone.

My '96 had some blue/white smoke on start-up. It had at some stage been
oil-change abused, as it has some black tar-like deposits in the oil-filler
neck. I changed the oil using 20-50 as indicated in the driver's manual for
summer here, and the smoke disappeared. In winter, I use 10-40,..still no
smoke.

Jason

Here's another reason to be glad you're not replacing the valve seals.
Was reading the factory service manual last night, and there is are
several special procedures for removing and replacing camshafts. The
one that caught my attention is the way to avoid _breaking the head_
when installing or removing them. Because the thrust clearances are so
close, if the hardened steel camshafts are inserted into (or removed
from) the aluminum bearing holders at a slight angle they can crack, so
one needs to observe the angle of the locating pin on the end of the
camshafts such that they rest evenly on, for example valves for
cylinders one and three, and with the exhaust camshaft it has to be
carefully "rolled" into position along the cam gear.

If you were only gonna do the exhaust ones, I think all your money and
effort and time would be wasted and you could possibly do more damage.
Change that oil to Pennzoil high mileage and put on a toyota or
purolator filter first. Then if you
need to add the additive you mention...I hate any additives myself but
at least try the oil change first. You would not put that additive into
dirty oil would you? Not sure what oil or viscosity you are using but
if your running 5w-30 maybe its time for 10w-40
which I use during the summer heat.
Here is another reason. Camrys rear main seals when they get old will
harden and leak oil, PLENTY of oil on your engine and the ground. I had
one fail on my old camry before they made the high mileage oils.
Transmission has to be pulled to replace seal, very costly.