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Recently, to commemorate the millennium,
I began a series of articles posted on our web site,
www.iskycams.com,
entitled “Tech Tips 2000.”
The first ten or so are under the heading
“Modern Myths of High Performance.” I decided
to write them because I didn't necessarily enjoy repeating
myself
over and over in order to undo the misinformation rampant
in our industry.
So, like “Tech Tips 2000,”
Cam Session is intended to set the record straight with
the truth, the whole truth and nothing but, so help
me.
Ron Iskenderian: will be setting
the record straight in each issue of Drag Racing Online.
If you have any questions concerning cams or valvetrain
components or tech, just email camsession@racingnetsource.com
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Cam-Timing Mythology:
No it didn't end with Ancient Greece
In the movie "The Bridges at Toko-Ri", (a Korean war era drama), Frederick
March plays a Navy Admiral who is notified of the death of one of the
pilots under his command (played by William Holden) who had been shot
down during an air raid and was like a son to March in the movie, having
given up a successful career to serve his country. The Admiral's tribute,
after hearing of the young pilot’s death, is one of the classic lines
from a bygone era, when unlike today the quality of the script was far
more important than any action scene or stunt. “Where do we find
such men?” he asked. A great line from a great movie delivered
by one of our finest actors (thanks to an excellent screenplay).
Why do I mention this in an article about cam timing? Because the script
writers from the good old days of Hollywood aren't the only journalists
who have “gone with the wind.” Technical writing has also
taken a hit in recent years. In the case of High Performance today,
I am generally not very impressed with what I see coming from the magazines.
People seem to have forgotten the two most important rules in writing:
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Get your facts straight
-
Omit needless words.
Why? Because all the words in the world won't make up for incorrect
assertions and nothing is better than the plain truth, simply stated.
Recently (for the umpteenth time) I received a phone call from a customer
who, like many others, had become a victim of High Performance misinformation.
He had been told by another misinformed individual that when aligning
cam timing marks on a Chevrolet V8 engine (cam mark at 6 o'clock, crank
at 12 o'clock) that the crankshaft's keyway slot would be a the 2 o'clock
position, and the piston would be at T.D.C. ignition (compression).
All true except for one small detail. The piston would be at T.D.C.
alright, but not on the compression stroke! Top Dead Center overlap
(opposite of compression) is where you would be with the marks aligned
in this position. Actual T.D.C. Compression is when both cam and crank
timing marks are at 12 o'clock high, one revolution of the crankshaft
away.
You're probably starting to get an idea of what came next. “How
can I set my ignition timing on overlap?” he asked. I spent nearly
20 minutes on the phone reassuring him that his cam was not ground incorrectly,
and let me tell you, it was a struggle. For you see, once something
like this gets into print it tends to be taken as gospel, whether or
not it is true! What finally turned the tide was when I got him to understand
that the engine doesn't know which T.D.C. it is on until the cam tells
it. He finally realized that his timing marks were in alignment every
other revolution and that he should be observing the motion of his engines
valves to verify T.D.C. compression, in order to set his ignition timing.
Where did this misinformation about cam timing marks alignment and
T.D.C. come from? His friend had seen it in print somewhere (kudos to
some magazines), and taken it as gospel. In fact, like respected engine
builder, Joe Sherman, I've seen it in the print media too, along with
other inaccuracies (my favorite is “advancing the cam increases
top end power but hurts the bottom end torque.” No, I'm not kidding,
and it's happened more than once.)
I do not know the name of the person responsible for originally putting
out this misinformation. He alone is not guilty however because others
have perpetuated it. This is a perfect example of why you should abide
by the old adage, “Believe little of what you hear and only half
of what you read in the press.” Why?
Because the print media in this country is in a sorry state of affairs.
Newspapers and magazines forsake accuracy in order to slant stories
in favor of political and big business interests. Book publishers gleefully
distribute a product which is, in reality, often so bad it is unreadable,
while talented authors struggle to get published. Is it too much to
ask that within the High Performance industry we deserve more than the
sub-par performances that some magazines, their writers and editors,
have been delivering? We need accurate, concise distribution of technical
information within our industry. If it is to happen, we must begin with
qualified journalists who really understand what it is they are writing
about. Where do we find such men?
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