Heads - Open vs. Closed?

[ViperMan]

Okay I've been sitting here (kinda bored) doing all kinds of searches on stroking, compression ratios, pistons, quench, etc...

Most of my searches have been fruitful because other people are asking the same questions I have.  However everyone seems familiar with the concept of open or closed heads, so no one's asking what that means!

So what's the difference?  And what would a 902 or 906 head be?  Advantages/Disadvantages?  What does the difference between open or closed dicatate when it comes to things like valve choice, piston choice, or compression ratio choice?

I'm trying to keep my questions to a minimum. 

Jeff

[Pistol Gripper]

Here's a good article on mopar heads:

http://www.moparmusclemagazine.com/techarticles/5115_cylinder_heads/index.html

http://www.moparmusclemagazine.com/techarticles/5118_cylinder_heads_ii/index.html

http://www.moparmusclemagazine.com/techarticles/5120_cylinder_heads_iii/index.html

P.G.

[Chryco Psycho]

open chamber heads are emission heads & are raised above the deck surface over the whole piston top , closed are D shaped chambers & are left at deck height over approx 1/2 the piston area, 906 are open chamber as are all heads after 67 , the chamber design has no effect on valve size , but piston shape has to be carefully selected to get quench & control the compression ratio . The only way to get quench is to use a closed chamber head which in my opinion is a big advantage