CCing Heads - How To - Pontiac GTO Forum
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post #1 of 3 (permalink) Old 05-05-2018, 04:09 PM Thread Starter
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CCing Heads - How To

Finally getting around to doing this. It is important to know, or have a good idea, of how many CC's your particular head's combustion chamber is. This is important when trying to figure out the big question of Compression Ratio. Pontiac advertised the combustion chamber CC's and websites will also give you that number, but those numbers are typically off and less than accurate. Then if your heads have ever been modified or cut, you could have a greater unknown as to the actual CC's of your heads. So here is a simple & inexpensive way to check and at least get pretty darn close.

Pic#1 shows the tools needed. Small Level, Food Coloring, Flat Plastic Panel, & Vaseline. The Plastic Panel is what you will place over the combustion chamber to seal it so you can fill it with a measured amount of liquid - water with food coloring added. I used an acrylic photo stand that was on sale for a couple bucks, but a piece of plexiglass would probably do the job - just don't get it too thin and flimsy. You can see it is 5" wide, so it was probably for a 5"x7" photo. The acrylic panel is pretty sturdy. I used my die grinder and cut-off wheel to cut off the base and then cut it off at the top where your photo would normally slip in. Then grind the edges smooth so it lays flat. No doubt you could use a jig saw to cut it as well.

You will need to drill 2 holes in it - I believe I used a 1/4" drill bit, but the hole size has to be a little larger than the end of the syringe you will be using. Where? I placed my panel over the combustion chamber and simply marked where I wanted the 2 holes which need to be within the combustion chamber area. I want one near a chamber edge which I will call the "top" and the lower hole to be about 3/8"-1/2" away from the chamber wall. You will be adding your water/food coloring at the hole at the "top." The other hole acts as a vent.

The Vaseline will act to seal the plate to the head surface. I suppose you could use some Vicks Vapor Rub, light axle grease, or even tooth paste (maybe?), but I use the vaseline.

The Syringe come from my local pharmacy. You will see articles that use a graduated glass burette & stand which we all used in out science classes, but why? I'm cheap and I'll never have a use for a glass burette -even when measuring the exact ingredients for an experimental alcoholic concoction. Now it may take a little convincing to get your pharmacist to give you one of these for free (because they are thinking "drug user" when they see me and my tattoos), but tell them you need it to measure the CC's of the combustion chamber on a Pontiac head so that you can calculate the needed compression ratio for pump gasoline with the ethanol in it. They won't have a clue what you just said, but it sounds scientific and not "druggy." Mine is a 12 Milliliter syringe which is the most common among drug users like me of course. 1 milliliter is equal to 1 CC for our purposes.

Pic #2 are the stands I use to hold up the head. Got these at Harbor Freight for real cheap - made in China. They are called "V-Shape Hang All" by StorHouse. Should be able to find these at a number of places as I have seen them in other stores. I drilled a hole at the top arch which a short 9/16" bolt/washer/lock washer will go through. This bolt will be used to attach them to the side of the head to act as legs. I suppose you could also use two flat pieces of bar stock, drilling matching holes at one end, which would then create a set of legs by passing your bolt through the holes and bolting to the head. The "Hang All" just seemed convenient & cheap.

Pic #3 is the combustion chamber on a 4X head I just picked up. I only cleaned one chamber. Used brake cleaner, green scuff pad, and wire brush to get it fairy clean. Make sure the head surface is nice and smooth as this is where you will lay the plastic panel. Also, do not forget to insert a spark plug to seal off the spark plug hole and it is needed to get an accurate CC reading.

Pic #4 is what the head looks like with the attached "Hang All" legs. Don't get carried away with tightening the bolts & crush the tubing. Tighten just enough to keep the head from rotating on you.
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post #2 of 3 (permalink) Old 05-05-2018, 04:25 PM Thread Starter
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Pic #5 & #6 shows getting the head level on the table. You want to get the head level in the two directions to aide in filling the combustion chamber evenly. It will also be used to allow trapped air to escape as the combustion chamber gets closer to becoming fully filled with the water/food coloring mix. I keep my bolts that hold the legs to the head snug, but loose enough so I can rotate the head to get it level. If it is off in the lengthwise span, you can put some shims of some sort under the legs to get it level in its lengthwise span.

Pic #7 is where we use the Vaseline. With the head now level, put a light coating on the head surface around the combustion chamber. The Vaseline is what will make the seal between the head surface and the plastic plate. You don't want any liquid to run out between the two. The amount you put on will not be uniform, so don't be concerned. Just put a thin even layer as best you can first - you will see why in the next picture.

Pic #8 is the plastic panel laid on top of the vaseline and combustion chamber. Most important thing here is to make sure that your "top" hole, or fill hole, is right at the edge of the combustion chamber edge. There is a reason for this which will be seen later. Once you have the plastic panel laid on top, push down on it to seal it to the head surface. You may see some of the vaseline squish out into the combustion chamber. A little will not hurt. A bunch of it will and means you put on too much and should redo it by taking the panel off, wiping off all the vaseline and then put a lighter layer on and repeat. It is also ok if you shift/move the panel around a bit. I actually do this a little after seating the panel to the surface to get a little better/even seal of the vaseline - seems to work.
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post #3 of 3 (permalink) Old 05-05-2018, 05:03 PM Thread Starter
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Pic #9 is all the great stuff to make the colored water and the syringe. Being a single guy, I can grab any bowl, dish, pot, pan, or other food holding item and use it without getting yelled at. So Corelle came to the rescue for my food coloring bowl. If I had China, I'd have used it instead. I used red to color my water. Then insert the end of your syringe into the water and draw the elixir of combustion chamber life into it. Draw about 11 ML into the syringe as you will have trapped air in it at first. Turn it upside down like in the movies to allow the air to escape unless you want to inject air into the veins of the combustion chamber and kill it - or if you don't want an accurate reading. Now push the plunger until it lines up with 10ML. You should have no air in the chamber or tip. This is the only time you have to do this as I found that from that point on, liquid will stay in the tip to keep air out each time you draw another round of water/food color.

Pic #10 shows the syringe with its 10 ML of water inserted into the "top" hole of the plastic panel. Simply inject the liquid through the hole and into the combustion chamber. Refill and repeat. I ONLY fill the syringe up to 10 ML each time as it is easier to keep track. I know that the combustion chamber on the 4X head is said to be about 98 CC's on a 400CI engine. So with this, I will load up my syringe to 10 ML each time for 9 times or a total of 90 ML (90 CC's).

Pic #11 shows what you should see at 90 ML of liquid. It is just reaching the full stage and the liquid will adhere to the plastic panel and be very obvious. You will see an air bubble form along the edges in the combustion chamber. This air is now trapped as the vent hole has now become useless because of its location. So stop at this point because we have to get that trapped air out which will be seen in the next picture.

Pic #12. What I did here was to put a piece of tape over the lower hole to seal it off so no liquid will run out. You are going to use the "top" hole as your vent. I tilt the head slightly (attaching bolts should be loose enough to allow you to tilt the head slightly) so the trapped air/bubbles will go to the "top" hole. Tilt as far as needed only to get that air to the top. Then I fill my syringe another 10 ML knowing that my combustion chamber should be 98 CC's. 10 ML gives me a little extra as these heads are not always accurate. I slowly fill the chamber through the "top" fill hole and watch the air pocket get filled in. You can tilt the head back towards level as it fills. You don't want to let the liquid spill out the fill hole. Eventually with a slow and steady hand, you will continue to add the liquid until it fills right up to the fill hole. The head should be level at this point and you won't see any air. This is why it is important as to where you place the "top" fill hole so it does not add to the problem of trapping air - it eventually becomes the vent as the chamber is completely filled.

You should not use all the liquid in the syringe. What ever is left is deducted from the 10 ML you just put in, so if you had 2 ML showing on the scale on the syringe, it would mean you used 8 ML. Add this to the 90 ML you already used and you have a total of 98 ML, or 98 CC's. This then tells you that your combustion chamber is indeed what the factory claimed it to be - 98 CC's. it seems to be the case, the head chambers are typically a couple CC's more than advertised. This held true with my 4X head. The combustion chamber was exactly 100 CC's which is 2 CC's more than advertised.

Now that you know what your chamber size is, you can mill it to reduce the CC's or even different valves can reduce it a few CC's. With the known CC's of the combustion chamber, you can now go about selecting your pistons that will provide a piston top with its CC's to arrive at a compression that will work for your application.
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