Originally Posted by cross-country
I'm guessing by measuring the amount of air displaced by running the motor through.
A clear solid tube with calibrations down the side of the tube.
Out the bottom of the tube is a hose with a screw in adaptor on the end of it.
In the tube is a plug that cam move freely up and down the tube.
Pull a spark plug, screw the hose from the tube into the spark plug,
crank the motor over.
There maybe be slight variations between engines due to running different cam shaft profiles.
But the testing guy after awhile can pick if an engine is not reading how it should.
There was a guy breaking records all the time, NHRA.
he used to come in at the right capacity engine.
Theway the car was built one cylinder was easy to get too,
the other seven were down right pain in the butt to get the plug out.
So scrutineering would check the easiest cylinder to get too.
Not thinking that the other seven cylinders were over capacity :)
Which they were.