DeTomaso Mailing List: August 99, Message #316

Cristiano asks;

'Can anyone please explain to me why it is a good idea to degree a cam, and
what you actually do when degreeing it. Can you do anything else than seeing
at how many degrees (0, +4 or -4) you have installed the cam yourself?'

According to Smokey Yunick - "You must absolutely do it!.The reason is so
many things can alter the phasing between the camshaft and the crank. Four
mechanical elements in the cam drive affect the camshaft phasing.

1) The keyway in the crank
2) The keyway in the crankshaft chain sprocket
3) The drivepin  in the nose of the camshaft
4) The drivepin pilot hole in the camshaft chain sprocket

These components are generally manufactured to reasonable tolerances, but
there are going to be variations when all these things are bolted together."

Most of us when rebuilding our engines use a new timing chain, and cam from
different manufactures than the crank. It seems reasonably likely there
would be some variance.  The last engine I lent a hand on rebuilding was
Kirby's, and if my memory serves me correct ( I am sure he'll correct it if
I am wrong), he uncovered his assembly was a couple of degrees off which he
corrected.

If you don't degree your cam, it may not be worth losing sleep over it as
several paragraphs later Yunick almost contradicts himself.
    "Modern camshafts are  extremely sophisticated, and if you move the
phasing plus or minus four degrees, you generally won't find much change in
overall horsepower.  In some instances you may significantly change the
torque output- If you advance most cams (Cristiano, this addresses your
second question) you will get more midrange torque but you will at the same
time ALWAYS lose top-end power- but in general, it isn't going to make a
real big difference."

Go figure, he later goes on to talk about the importance of checking the
degreeing on every lobe to uncover possible manufacturing variances in the
cam.

FWIW, my cam calls for installation 4 degrees advanced.

John T