measuring combustion CC?

[John Van Nghiem]

Hey guys,

just saw John Denman's post on the 7.5cc in K1.

What's the proper way to measure the CC?

thanks.
John

[John Denman]

The correct way requires the additional LAD tool, but to get close enough, either way requires a calibrated Burette. Available from most Scientific stores.

Use Marvel mystery oil as the liquid.

Ready?
1) Fill the Burette with Marvel Mystery oil about 1cc above the zero mark. Let the tiny bubbles rise to the top (about 30 seconds). Drain off the excess to zero (also fills the dispense at the bottom.

2) Tilt motor so the cylinder is straight up & down. Bring Crank to TDC.

3) Fill cylinder from burette to bottom of spark plug threads. Move cank a few degrees back and forth to bring fluid to top to nail TDC. With TDC nailed, fill to top of sparkplug hole. Thats the key measurement.

Actual CC would subtract the sparkplug hole, but many things can be done to cheat around this make more compression. Spark plug hole is about 2 CC.

That simple.

[John Clasen]

Back up to where John said use the LAD cc fixture. Trying to eyeball the fluid at exactly where the threads begin is impossible. That is why the LAD tool was made. The tool volume is exactly 2cc. So you just screw the LAD fixture into the head (including any sprark plug spacers that were in use when the kart came off the track) fill the cylinder with the appropriate fluid from an 'A' standard scientific burette and read the results at the bottom of the meniscus.
When you subtract the two cc volume of the calibrated fixture, you will have the actual
combustion chamber volume or CCV for that engine combination.
Thanx, J.R.

[Dennis Brown]

What JR described is the proper way to determine your actual combustion chamber volume. However, so as not to confuse anyone when a cc # is called out for tech there is no use of spark plug spacers under the LAD tool, and the volume of the LAD tool is not subtracted.
DB