What are the chances in the vortec combustion chamber that make them so "neato". What makes them less prone to knock? What size combustion chambers do they have, 58cc? Also, Does the size of the combustion chamber of a given set of heads effect the power/combustion? Like If i built a block around a set of 58cc and 64cc heads both at 10:1 compression would one make more power than the other? One be less likely to knock? Thanks ------------------ 1985 Iroc-z, 14 second 305, new engine in the works.

Vortecs are advertised as 64cc, but some say they're closer to 61cc.

The rest of your question can get complicated. Are you talking about a 305 or 350? That's important, but I'll address other generalities first.

Generally speaking, a larger chamber allows the valves to be less "shrouded", and therefore should flow better. But, flat top pistons tend to use the generated pressure better than raised dome pistons. So, those things can offset each other.

A 10:1 305 with 64cc chambers is going to have to have pop-top pistons. The extra flow of the larger chambers probably isn't going to help much because the small bore is going to shroud the valves anyway, and the raised dome is going to hurt you. No reason to go that way. For reference, a stroked 305 to 334 will have 10:1 with 58cc chambers and stock deck height and gasket thickness.

In a 350, you can get 10:1 with 64cc chambers and flat tops by controlling deck height and gasket thickness. A well-designed 58cc chamber with D-shaped valve reliefs might make even more power, though.

Lots of variables. 58cc chamber 350 heads are typically aluminum, which make less power than identical iron heads, but the weight savings can make them worth it.