Precision Measurement Supply - Fixtures, Tooling And Measuring Devices For Professional Engine Builders

Cylinder Head CC Kit Instructions

Introduction

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!

Procedure

  1. Start 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.

  2. Have 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.

  3. Complete 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.

  4. Coat 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.

  5. Block the head up so that one side is slightly higher than the other.  This will help you get the air bubbles out.

  6. Coat the periphery of the combustion chamber with grease – white heat-resisting brake grease is easy to see and works very well.

  7. Place 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.

  8. Carefully assemble the burette, stand and clamp.

  9. Using 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.  

  1. With 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.

  2. Fill the chamber until the fluid just touches the BOTTOM of the hole.  Be sure ALL air bubbles are out.

  3. Carefully read and record the amount of liquid metered into the chamber.  (Remember what was mentioned about meniscus.)

  4. Repeat procedure on remaining chambers.

  5. After 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 mind:  Once 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.  NOTE:  Only sink the exhaust valve – never the intake.

  6. After 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!

  7. The 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.  

The following procedure will allow you to determine the amount to be milled from the heads.  

A.  Clean and assemble the heads.

B.  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.

C.  Fill burette to the exact amount of fluid that the FINISHED chamber should contain – minimum legal CC’s and safety margin for carbon buildup.

D.  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.

E.  The reading on the micrometer is the amount to be milled from the head surface.  

This 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

We 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!  

  1. Finally, it’s a good idea to check the stem height of each valve and grind them all to the length of the shortest one.  Put them back in the same place you got them from!  

 How to Figure Compression Ratio

The compression ratio is simply a ratio between the filled and compressed volume of the cylinder.  When figuring this ratio, you are dealing with four variables:  

1.  CYLINDER VOLUME  = .7854  X  BORE2  X STROKE

 2.  DECK CLEARANCE VOLUME     The volume between the top of the piston deck and the top of  the block when piston is at T.D.C.  Deck clearance is measured with a depth micrometer and deck   clearance volume is computed as follows:   

0.7854  X  BORE2  X  DECK CLEARANCE = DECK CLEARANCE VOLUME

3.  HEAD GASKET THICKNESS VOLUME  =  0.7854  X  BORE2  X  GASKET THICKNESS

4.  COMBUSTION CHAMBER VOLUME      Record when CCing heads.