Cam Degreeing

by Ron Rygelski


Ok, so you say you want to change the cam in your Buick for even
more asphalt shreading, driveshaft tortureing torque and horsepower.
Cool! Your buddies tell you to just stick it in--that degreeing is
complicated and unnecessary. Not cool! Here's why:


"What do we mean by "phasing" or "degreeing"?"

This simply means that we are going to verify that the installed
position of the camshaft is correct relative to the position of the
crankshaft. This is very important because the timing of the valve
events in relation to piston position is crucial if maximum power
production is to be achieved.


"To degree or not to degree?"

Any part that can be machined can also be mis-machined. Your
new cam has a couple of bolt holes drilled through the flange that
hold the upper timing gear in place. Are they in the proper
position? Says who? How about the keyway cut into the lower gear?
How about the dots stamped onto each? Then there's the crank keyway,
the timing chain, and the list goes on. Errors in each may be small
(or they could be large), but they pile up. Degreeing will insure
that the cam is, in fact, installed correctly, and allow you to take
measures to correct if it is not. This helps to insure that your
Buick will be fast and furious! The advantage to not degreeing is
that you get done sooner. Your choice.


"What kind of tools do I need?"

Degreeing a cam involves some careful measureing (uh-oh), but
it's really not as complicated as you may have been lead to believe.
You are going to need a 0-1" dial indicator and a holding fixture
(magnetic base). This is a simple tool that allows precise
measurements of lobe lift to be taken. These items come in very
handy for all sorts of engine assembly procedures, as well as other
work, so if they're not already part of your toolbox arsenal, they're
a good investment. You're also going to need a degree wheel (try to
find one that is marked in ATDC and BTDC degrees rather than one that
is simply marked 0-359--it makes things a whole lot simpler). You
will need a pointer of some sort (one can simply be fashioned from a
coat hanger). Finally, you'll need a piston stop. If the heads are
off the motor, simply use a piece of scrap steel (1/4") an inch or so
wide and long enough to span across the deck surface. Drill two
holes corresponding to head bolt holes for the #1 cylinder, and a
third hole that will line up with the center of the piston with the
steel fixture (a minute ago it was a junk piece of steel--now all of
the sudden it's a fixture) bolted in place over the #1 cylinder.
You'll need two short bolts (1-1/2") in the same diameter as the head
bolts, and a third for the center hole (diameter unimportant) along
with two nuts. If you are doing this with the heads on the car a
comercially available piston stop that threads into the sparkplug
hole can be used, or one can be fabricated from an old sparkplug.
That's it. Nothing extravagant.


"Ok, I've got my tools, now what?"

Now we get to play! The first step is to find true TDC (top
dead center) for the #1 piston. Now, you cannot eyeball this--it has
to be exact TDC. To find it we're going to use our piston stop,
pointer, and degree wheel:

1: Find true TDC for #1 piston.

Let's assume the heads are off the motor. Bolt the steel
fixture we fabricated to the deck surface directly over the #1
piston. Adjust the center bolt using the two nuts so that it will
contact the piston about 1/4" or so before it reaches TDC. Now,
securely mount your degree wheel to the crank snout (orientation at
this point is unimportant). Fabricate a pointer out of a sturdy coat
hanger with one end filed to a point and securely bolt it to the
front of the block so that it is pointing to the marks on the degree
wheel. Rotate the crankshaft clockwise by hand until the #1 piston
hits the stop, and mark the degree wheel at the location of the
pointer. Rotate the crankshaft counter-clockwise until the #1 piston
contacts the stop, and make a second mark on the degree wheel at the
location of the pointer. TDC for the #1 cylinder is exactly halfway
between these two points. Make a mark exactly halfway between them.
Now, remove the piston stop from the deck surface, and rotate the
crank so the pointer is at the new mark you just made. The #1 piston
is now at exact TDC. Finally, loosen the degree wheel and rotate it
so the pointer is pointing at the printed "TDC" mark on the degree
wheel, and tighten it back up. The degree wheel is now indexed to
the motor (TDC mark indicates true TDC for #1 piston. You can re-
check your work by re-installing the piston stop and rotating the
crankshaft clockwise, then counter clockwise. The degree wheel
should show the same BTDC and ATDC numbers.


"Time to degree?"

Yes, my anxious leadfooted friend, it's time to degree. I like
to use the intake centerline meathod because it's so simple. Here's

2: Degreeing using the intake centerline method:

Now we're going to get to use the dial indicator and the cam
card (hopefully included with the camshaft!). First, install a
lifter on the #1 cylinder's intake lobe. Set up the dial indicator
so that it is parallel to the lifter bore using the magnetic base
fixture and so that it is actuated by the lifter (make sure the
plunger of the dial indicator is contacting the rim of the lifter
body and NOT the plunger for accurate measurements and that the dial
indicator is slightly preloaded at zero lift. Rotate the crankshaft
by hand until the dial indicator shows maximum lobe lift, and zero
the indicator (by turning the faceplate until it reads zero). Rotate
the crankshaft clockwise until the indicator reads -0.030" and record
the degree wheel reading. Continue to turn the crankshaft clockwise
(almost two revolutions) until the indicator again reads -0.030" and
again record the degree wheel reading. The installed centerline is
halfway between those two numbers (add them together and divide by
two). The cam card provides you with the manufacturers suggested
intake centerline. Compare this with your installed centerline. If
you are within a degree then you're all done and you can finish
buttoning up the motor. If not, we've got a little more work to do.


"Well, it's what?"

That depends on by how much. Two degrees is a borderline case.
Most guys would let it go--personally I'd correct it. More than two
degrees will definately require correction.

3: Adjusting the cam:

The best way I've found to adjust cam timing on the Buick engine
is to use one of the 9 keyway timing chain sets available from
several of the Buick vendors. These are quality sets, and make the
job very easy, so it's money well spent. If you know your cam to be
installed, say, 4 degrees advanced and you wish to correct this
to "straight up", then you will need to retard the cam by 4 degrees
using the multi-keyway set. Simply select the -4 keyway to put the
cam in the desired "straight up" position, being sure the dots align
during installation (the dots must line up regardless of which keyway
is chosen).

Ron Rygelski

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