Ratios?

I was wondering, when people talk about ratios like 18:1 or 13:1 or anything like that then what are they talking about. I am guessing fuel to air ratio right? And does it mean the same thing when they talk about getting pistons that have a certain ratio? If someone can please explain this in some good detail then it would be greatly appreciated. Thanks.

That's your compression ratio. Techinspector1 wrote this excellent compression ratio explained thread, here it is, I would never be able to explain it as good as Tech has so that's why I'm directing you to that post through this link. http://www.clubhotrod.com/forums/sho...ression+ratios

Ay thanks a lot man, I appreciate the help. I checked it out and all now... kind of hard to understand, but I understand most of it and there are things here and there that I don't understand.... Thanks again!