I want to get a set of forged pistons and a good set of rings, but I have no idea what I'm looking for. I have a few questions for you pros.

1. Is .030 stock bore size.

2. explain bore size and the effect

3. Flat top, dome top, what does it all mean?

that's really about it. I'm just not to educated on this area.

thanks

Jason S

 

let see what I can do here:

1&2: The bore of an engine is otherwise known as the diameter of the piston. the stock bore size is refered to as std (or standard). A cylinder needs to be bored(made bigger) when somebody wants a bigger engine or if the cylinder walls have scratches on them. a SBC(small block chevy) can be bored to a max of .060, but usually people feel safer at .030 because of thicker walls. If you bore a STD 350 to .030 you can make it a 355, if you bore it to .060 if probably becomes a 360. A 350 has a 4.0" bore, and a 305 has a 3.75" bore. You cannot bore a 305 to a 350.

Bore combined with Stroke create engine displacement. Stoke is the distance the pistons travel in the cylinder(up and down) while bore is the diameter.

3: Pistons need to be ordered according to the bore. a STD piston be too small for a .030 bored block and vise-versa. A flattop piston is exactly that. it has a flat top with some reliefs(dents) for the valves. A domed piston is exactly that. It has a dome to make the combustion chamber smaller and raise compression. A "dished" piston is the opposite of a dome, it reduces compession by making the combusion chamber bigger. think of the bottom of a pepsi can as a dished piston, and the opposite would be a dome.

Hope this helped!

 

I think alot of people have accidentally left an aluminum can in the freezer for too long before, so if you need an example of a domed piston, thats what it would be... a bottom of a Pepsi can left in the freezer too long.

 

Great illustration.

Thanks!!!!