Piston ??'s

[trueblue450]

Now, I have been on here for awhile and learned a lot of stuff, but there is still something I have been wondering. What does 10.8:1 those numbers mean. Everyone types in I want a 101983049283 piston. I just wanted to know what the 3 numbers meant, and how they affected the engine. Thanks

[Wheelie]

The numbers 9:1 or 12.5:1 describe the difference in cylinder volume at BDC and TDC.

9:1 means when the piston is at BDC there is 9x more air volume in the cylinder than there is at TDC.

[Drtridr18]

simply put, it's a ratio. like the seond number is the reference, the first decimal (10.8) is the important one

more is better, higher compression=more power, also more heat