It is important to level and secure the head when doing cc measurements V-style... (Photo
How To Measure CC Volume We have established that determining the volume in the chambers is critical. Now, how do you measure this volume? First, you will need some specialized tooling. Don't worry, specialized does not always mean expensive, at least in this case. It is important to have a way to hold the head so the chambers are held facing up and are level. This type of head stand is available from any number of tool suppliers that service the performance and racing industry. Powerhouse Products is one company that sells several different types of head stands.
Then, you need to cover the combustion chamber so that it is possible to fill the chamber with fluid. The cover can be something as simple as a piece of Plexiglas with a small hole in the center. The Plexiglas needs to be large enough to cover the chamber and rest on the flat part of the head. This can be purchased at the local hardware store or one of the larger home improvement centers. A piece about 5x5 inches will be just fine; the thicker the better.
You need some grease to coat the head at the "Plexiglas to head" interface to keep the fluid you will be using from leaking out of the chamber as you fill it. You also need a fluid to fill the chamber. Mondello prefers alcohol with food coloring so the fluid in the chamber can be seen as the chamber is being filled. You can also use very thin oil, such as Marvel Mystery Oil. The fluid must be thin and visible.
...or peg-style head holders do the job nicely. (Photo by Powerhouse Products)
The next item needed is a burette. Just as a point of reference, a burette is a glass or plastic tube with graduated markings on the side, usually marked off in cc's, that has a petcock on the bottom. The top is open, so you fill the tube with the fluid you plan to use for measuring your volume. Once you fill the burette to the top, use the petcock to slowly let out fluid until you lower the fluid level to the zero mark. The zero mark will be very near the top of the burette. After the burette is filled, it is a simple matter to just fill the chamber and record the volume that leaves the burette.
Great care must be exercised to ensure that the chamber is filled completely and no fluid is spilled. Once the chamber is filled, it is a simple matter to view the burette and see how much fluid was required. Depending on the size of the burette, you may have to refill the burette to fill the chamber. If that is the case, make sure you write down how much fluid you have placed into the chamber. While this is not a complex task, it can be avoided by using a larger volume burette.
Once you have filled all the chambers and have the numbers in front of you, make some decisions depending on the outcome. If the chambers are too small, you have to increase the size of the chamber. This can be accomplished by doing the following:. Simply grinding some material out of the chamber. Great care must be exercised in this process. The shape of the chamber can and will affect flow numbers, so care must be used.. Adjusting the valve job to sink the valve lower into the chamber. Once again, great care must be exercised and you must not go too far.. Using different valves that may have more dish on the face or remove material in a lathe from the face of the valve.
There is nothing to be afraid of when it comes to the tooling required to measure cc's. A
If the chambers are all too big, the options are just a bit more limited. Just like drilling a hole, it is always easier to make the hole bigger than to add material to make the hole smaller.. You can mill the head to reduce the volume in the chambers. You can change the valves so they have less of a dish shape on the face. Changing the head or heads is also an option
There are many different heads on the market today. The selections we have now are much broader than when the only choice available to you was what the OEM's had available. You may be constrained by the engine rules of the class in which you race, so the selection process just gets easier.
As the constructor/engine builder, you make the choices. You make the final determination as to the final chamber size. You have the power to make power. In today's racing environment, we have to pay attention and know these kinds of details in order to improve our performance. In order to know, you must measure. The goal is always to improve, so we must measure the cc volumes and equalize them if we expect to end up with a smooth-running, balanced engine. CT
Mondello Tech Center - 888/666-3355
Powerhouse Products - 800/872-7223