[SEL] Semi-OT: Engine valve alloys

[Richard Allen]

I have been doing some research on exhaust valve alloys and ran across
an interesting site. Check out the following:

http://www.automotiverebuilder.com/ar/ar99946.htm

The author mentions a pitfall that amateur and professional engine
rebuilders alike sometimes fall into that has the potential to do a
great deal of harm, which is using exhaust valves for intake
application. The thinking is that the exhaust valves are tough stuff
and will last longer. I never would have thought that it could cause a
problem, either, but according to this article it can. Of course damage
from doing the opposite of installing intake valves in the exhaust
seats is quite obvious. 

On a few of the many engines that I have worked on, the valves were not
marked according to being intake or exhaust and they where both the
same diameter. After cleaning them up and resurfacing it may be
difficult to distinguish them. Quite fortunately over the years I have
had some really good teachers for doing engine work who pounded it into
me that EVERYTHING removed from an engine has to be marked where it
came from, including what rotational position it was in as well. So I
never have mixed up the intake and exhaust valves. At least not yet,
and my fingers are crossed! My dad taught me early on about lapping
valve seats as well. I was astounded after years of successful engine
rebuilding to find that a lot of engine shops don’t bother lapping the
seats. In a perfect world valve seats don’t need lapping, but without
the correct amount of tiny interference angle for break-in and not
being able to get the seats and valves resurfaced dead on center, not
lapping them is guaranteed trouble!  

The only time I got into deep, deep trouble was when I was rebuilding
my 1967 1.5 liter Volkswagen microbus engine. I had put the cam
follower-valve lifters into a papier maché egg carton with the position
numbers written on it. I accidentally shoved the carton off the
workbench and you know the rest. For broken-in cams and followers, if a
cam follower is mated with the wrong lobe they will grind themselves up
in short order, and I didn’t have the money to buy a new camshaft and
followers. This is why every mechanic needs a tube of Prussian blue
contact indicator compound! After applying a barely visible trace of
that wonderful blue grease on the mating surfaces it took me about half
an hour to try each follower on each cam lobe to check them for wear
patterns, and I found where each belonged! When the right follower was
with its mating lobe it was extremely obvious and there was no guessing
at all. I got two more rebuilds out of that engine. If you don’t know
what to get your buddy for Christmas or a birthday, give him/her a tube
of Prussian blue, Permatex/Loctite part number 80038. Dykem also makes
a good product but I don’t have their part number in front of me.
Besides using to check parts contact, I discovered it has another
extremely valuable use. If you have someone getting into your toolbox
or locker when your back is turned, or otherwise making life miserable
for you, take a gob of Prussian blue compound and put it on the
backside of the tool box drawer pull or locker door handle out of sight
but where they will get it on their fingers. Before they realize it,
they will have intense dark blue grease all over their hands, face, on
their clothes, etc. It doesn’t wash off easily and is just about
indelible on cloth. You could even put it on their door handles, too,
come to think of it. But we all know antique engine enthusiasts are
nice people and don’t do things like that.

Richard Allen