When it comes to planning out an engine build, one of the most important specifications in the long list of measurements, is the volume of your cylinder head’s combustion chambers. After your bore and stroke, combustion chamber size is the next largest factor in your engine’s compression ratio. Besides just housing your intake and exhaust valves, the combustion chamber shape and size can really increase the efficiency of your engine.
With all the development in the shape of the combustion chamber, they have become a highly irregular shape, which makes them incredibly difficult to measure the volume of through traditional means. Sure, if you have access to the CAD file for the porting program you could see the volume of the chamber pretty accurately, but the second you leave the digital realm and get into the real world, chances are that volume will stray from ideal.
If you were to touch up the chamber by hand, deck the heads, or even change valves, you need a way to check the new volume of the chamber so that you can accurately calculate your engine’s compression ratio. What about with a second-hand set of heads? You might know what the manufacturer’s specs were originally, but a lot of things can change between the manufacturer delivering a part to the original owner, and when it finally ends up in your hands.
In the case of scrapyard heads, you might not know what they were even supposed to be from the factory, let alone what happened to them before they found their way to the junkyard. So checking the combustion chamber volume is an absolutely necessary step in order to properly plan your engine build.
This kit from Goodson Tool and Supply includes everything you need to check your combustion chamber volume. A 100cc burette, a funnel, a burette stand, a sealing plate, and a cleaning brush.
How To Measure An Irregular Shape
In order to measure an irregular shape, we have to go back more than 2,200 years, to the days of the mathematician Archimedes. While he is credited with discovering a large number of principles we still use today, the one that applies here is the principle of displacement. That states that an object’s volume can be measured by the amount of water displaced when submerged.
Conversely, we can extrapolate that by measuring how much water it takes to completely fill a void, we can know the volume of that void. In our case, that void is the combustion chamber, in…
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