leaded or unleaded fuel

yellow rose said

You have no idea what the dome volume of the piston is unless you do a downfill and measure it. Otherwise it’s a guess, and probably a poor one.

Can’t count how many engines came through the shop that the owner said has XX.XX compression ratio and 99% of them were a point or more off.

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Yes, but what if the piston manufacturer says it has a certain dome volumn? Do you not believe them?
I absolutelyagree that lots of times people don't have the cr they think they do, because they simply don't measure. I have a trw "11 1/2 to 1" engine that is really in the low 10s, determined by actual deck height and chamber size measurements . I have another with arias "12 1/2" pistons that are more than .050 in the hole ( damned if I'm gonna deck a real max block .050 !), and with an 84cc max head is barely 11 to 1.