How to Measure Your Combustion Chamber Volume

We filled the combustion chamber completely.  As you can see the grease seals everything nicely.

Next we reweighed the cup to determine that we filled the combustion chamber with 57.5 grams of Motul ATF.  From Motul’s spec sheet, the density of the ATF is 0.845.  So 57.5 grams divided by 0.845 is 68.047cc.  We can round this off and say our combustion chamber volume is 68cc. Now we can figure out our true compression ratio if using a shelf piston or order a custom piston with our specified dome volume to get the exact compression ratio we want.

Not too hard right?


1 comment

  1. Very creative Mike ! I borrowed a 50 ml burette from work for this, and double checked one of the 6 chambers to verify consistency. My old GT6 had flat top pistons with a variation on distance from deck height to top of pistons. To compensate for this each head chamber had different volumes, so when bolted up, the total volumes were identical.

    I also borrowed a triple-beam balance for matching piston weights. Other balancing was done by a trusted machine shop.

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