It’s obvious you are a serious racer or you wouldn’t
have purchased our kit; however, we
would like to drill a few things into your mind before you start.
First of all, head CCing is not difficult, but it is time consuming
if done right. Secondly, your
results will only be as accurate as the person doing the job (anyone can
get a set of heads close). Your
goal is to get them RIGHT!
These instructions are written with the assumption that you
are building a set of heads for Stock
or Super Stock, where
polishing or metal removal is illegal.
If you do not fall into this category, DISGREGARD sinking the valve to gain volume and pick up your volume
the easy (and most beneficial) way by unshrouding the valves.
Sinking valves is a necessary evil for the stockers and is not the
H.P. trick of the week. The
more a valve is sunk, the more it is shrouded – so only sink a valve as
much as absolutely necessary and NEVER
sink the intake. Also, keep in
mind that once a valve is sunk, it CANNOT
be raised – so go easy!
Finally, before beginning, we suggest that you locate a COMPETENT
MACHINIST. A squirrel on
the business end of a Storm Vulcan can wipe out hours of work and produce
high-dollar boat anchors – believe it!
with CLEAN (as in spotless) heads.
Have the heads glass-beaded and boiled out.
It if is a stocker, and you are worried about glass-beading,
find a shop that will blast them with cracked walnut shells.
The point is: The
heads must be clean.
the shop that cleans the heads check the block mating surface for
straightness before starting. If
it isn’t straight, have the shop mill them just enough to true them
up – probably .002 to .003.
the valve job to the point of the final pass with the finishing
stones. NOTE: If you
don’t plan on sinking valves to obtain volume, go ahead and complete
the valve job entirely at this point.
valve seats with a THIN
coat of light grease and assemble the heads.
Be sure to use the same type of spark plugs for CCing that you
intend to run.
the head up so that one side is slightly higher than the other.
This will help you get the air bubbles out.
the periphery of the combustion chamber with grease – white
heat-resisting brake grease is easy to see and works very well.
the Plexiglas plate over the chamber, with the hole on the high side
and the counter sink up. Press
evenly and firmly to insure a perfect seal.
assemble the burette, stand and clamp.
either automatic transmission fluid or clean solvent with a couple of
drops of food coloring as a measuring fluid, fill the burette to the
“O” line. NOTE: The surface
of the column of fluid will appear to be concave (or sunken) in the
center. This is known as meniscus.
For accurate results,
align the marks on the burette with the lowest (sunken) portion of the
fluid for all measurements.
the burette positioned over the countersunk hole, and the head FIRMLY
blocked, slowly open the stop-cock and begin filling the chamber.
Watch for leaks at the seal of the plate and the head surface
(this is where the white grease helps).
If a leak develops, be very patient and START OVER.
the chamber until the fluid just touches the BOTTOM of the hole. Be
sure ALL air bubbles are
read and record the amount of liquid metered into the chamber.
(Remember what was mentioned about meniscus.)
procedure on remaining chambers.
you have recorded the volume of all the chambers, the next step is to
bring all chambers to the exact volume of the LARGEST one. This
is where sinking the valves comes in – (if rules disallow grinding
in the chambers). Different
people have different approaches to sinking valves.
The following is only a guideline.
If flow bench tests have proved better angles for your
particular heads, by all means use them.
To sink a valve, top the seat with a 15-degree stone to
unshroud the seat circumference. Check
the rules before making the top cut so you don’t get too wide.
Reestablish the seat with a 45-degree stone (or whatever your
seat angle is). Go very
easy on the first couple of chambers or you’ll sink it too far.
Make a light pass, clean everything, reassemble the head and
re-check volume. Keep in
it’s sunk, it can’t be raised.
It’s cheaper to check it three or four times and work up to
the volume than it is to hog it out the first time and scrap the head.
Only sink the exhaust valve – never the intake.
all chambers are exactly equal, you can finish up the valve job.
If the sinking operation left some of the seats too wide, they
may be narrowed with a finishing stone of a greater angle than your
valve seats – maybe 55-70 degrees.
Again, check your racing rules for maximum angles and depth of
bottom cut. You can get
illegal in a hurry!
next step is to bring all chambers down to the legal CC’s.
It’s not a bad idea to stay .5 to 1.0 CC over the minimum to
allow for carbon build up, etc.
following procedure will allow you to determine the amount to be milled
from the heads.
Clean and assemble the heads.
On a bench or solid table, get the heads dead level in both planes.
Use a machinists’ alcohol level if available – if not, make it
available – they gotta be level.
Fill burette to the exact amount of fluid that the FINISHED
chamber should contain – minimum legal CC’s and
safety margin for carbon buildup.
With the head perfectly level, use a depth micrometer to measure
chamber –- read mike just as the fluid
“jumps” to the tip of the micrometer shank.
The reading on the micrometer is the amount to be milled from the
is where that COMPETENT machinist comes into play.
Watch him and make certain he uses a dial indicator to indicate the
cutter with the head in both planes. If
you had the heads trued before starting, they will indicate zero run out,
and that’s what you want. Also,
make sure he uses an indicator to measure the depth of cut.
Backlash and wear may render the dial on the hand wheel inaccurate.
This sounds nit-picky, but remember what
said at the start – anyone can get them close – you want them RIGHT.
If the machinist won’t
do it right, you’re in the wrong shop anyway!
it’s a good idea to check the stem height of each valve and grind
them all to the length of the shortest one.
them back in the same place you got them from!
to Figure Compression Ratio
compression ratio is simply a ratio between the filled and compressed
volume of the cylinder. When
figuring this ratio, you are dealing with four
= .7854 X
when piston is at T.D.C. Deck
clearance is measured with a depth micrometer and deck
DECK CLEARANCE VOLUME The volume between the top of the piston deck and
clearance volume is computed as follows:
BORE2 X DECK
CLEARANCE = DECK CLEARANCE VOLUME
HEAD GASKET THICKNESS VOLUME
COMBUSTION CHAMBER VOLUME
Record when CCing heads.