CCs for flat top pistons
01-19-2014, 07:31 AM
#1
CCs for flat top pistons What # for piston CC do you guys use for calculating compression when using flat top pistons?
Reason I ask is that I've always thought of them as having 0CC, but recently an acquaintance mentioned that they really have something like -1CC due to the gap between the piston and the bore...so it's not a perfect 0 but acts like a small relief.
Is that true or is this kid splitting atoms with this theory? I can see this, but never thought it be anywhere near 1 full CC with the tiny gap between the pistons and cylinders.
Reason I ask is that I've always thought of them as having 0CC, but recently an acquaintance mentioned that they really have something like -1CC due to the gap between the piston and the bore...so it's not a perfect 0 but acts like a small relief.
Is that true or is this kid splitting atoms with this theory? I can see this, but never thought it be anywhere near 1 full CC with the tiny gap between the pistons and cylinders.
01-19-2014, 08:07 AM
#2
TECH Fanatic
Stock piston top ring lands are pretty thin, about 0.5cc of volume above the top ring. This applies whether or not the piston is dished.
Aftermarket piston ring lands are thicker (and smaller diameter), roughly 1.5cc of volume above the top ring.
Piston deck height also influences this volume when at TDC.
But yes, at the end of the day this is "splitting atoms". The calculator you're using may already take this into account, or it may not.
Here is a figure I made to illustrate the subject. Hope this helps.
Aftermarket piston ring lands are thicker (and smaller diameter), roughly 1.5cc of volume above the top ring.
Piston deck height also influences this volume when at TDC.
But yes, at the end of the day this is "splitting atoms". The calculator you're using may already take this into account, or it may not.
Here is a figure I made to illustrate the subject. Hope this helps.
